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rfc:rfc3103

Network Working Group M. Borella Request for Comments: 3103 D. Grabelsky Category: Experimental CommWorks

                                                                 J. Lo
                                                  Candlestick Networks
                                                          K. Taniguchi
                                                               NEC USA
                                                          October 2001
             Realm Specific IP: Protocol Specification

Status of this Memo

 This memo defines an Experimental Protocol for the Internet
 community.  It does not specify an Internet standard of any kind.
 Discussion and suggestions for improvement are requested.
 Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2001).  All Rights Reserved.

IESG Note

 The IESG notes that the set of documents describing the RSIP
 technology imply significant host and gateway changes for a complete
 implementation.  In addition, the floating of port numbers can cause
 problems for some applications, preventing an RSIP-enabled host from
 interoperating transparently with existing applications in some cases
 (e.g., IPsec).  Finally, there may be significant operational
 complexities associated with using RSIP.  Some of these and other
 complications are outlined in section 6 of the RFC 3102, as well as
 in the Appendices of RFC 3104.  Accordingly, the costs and benefits
 of using RSIP should be carefully weighed against other means of
 relieving address shortage.

Abstract

 This document presents a protocol with which to implement Realm
 Specific IP (RSIP).  The protocol defined herein allows negotiation
 of resources between an RSIP host and gateway, so that the host can
 lease some of the gateway's addressing parameters in order to
 establish a global network presence.  This protocol is designed to
 operate on the application layer and to use its own TCP or UDP port.
 In particular, the protocol allows a gateway to allocate addressing
 and control parameters to a host such that a flow policy can be
 enforced at the gateway.

Borella, et al. Experimental [Page 1] RFC 3103 RSIP Protocol Specification October 2001

Table of Contents

 1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . .  3
 2. Specification of Requirements . . . . . . . . . . . . . . . .  4
 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . .  4
 4. Architecture  . . . . . . . . . . . . . . . . . . . . . . . .  5
 5. Transport Protocol  . . . . . . . . . . . . . . . . . . . . .  7
 6. Host / Gateway Relationships  . . . . . . . . . . . . . . . .  7
 7. Gateway Flow Policy and State . . . . . . . . . . . . . . . .  8
 7.1. Local Flow Policy . . . . . . . . . . . . . . . . . . . . .  9
 7.2. Remote Flow Policy  . . . . . . . . . . . . . . . . . . . .  9
 7.3. Gateway State . . . . . . . . . . . . . . . . . . . . . . . 10
 8. Parameter Specification and Formats . . . . . . . . . . . . . 11
 8.1. Address . . . . . . . . . . . . . . . . . . . . . . . . . . 11
 8.2. Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
 8.3. Lease Time  . . . . . . . . . . . . . . . . . . . . . . . . 13
 8.4. Client ID . . . . . . . . . . . . . . . . . . . . . . . . . 13
 8.5. Bind ID . . . . . . . . . . . . . . . . . . . . . . . . . . 13
 8.6. Tunnel Type . . . . . . . . . . . . . . . . . . . . . . . . 14
 8.7. RSIP Method . . . . . . . . . . . . . . . . . . . . . . . . 14
 8.8. 8.8.  Error . . . . . . . . . . . . . . . . . . . . . . . . 14
 8.9. Flow Policy . . . . . . . . . . . . . . . . . . . . . . . . 15
 8.10. Indicator  . . . . . . . . . . . . . . . . . . . . . . . . 15
 8.11. Message Counter  . . . . . . . . . . . . . . . . . . . . . 16
 8.12. Vendor Specific Parameter  . . . . . . . . . . . . . . . . 16
 9. Message Types . . . . . . . . . . . . . . . . . . . . . . . . 16
 9.1. ERROR_RESPONSE  . . . . . . . . . . . . . . . . . . . . . . 17
 9.2. REGISTER_REQUEST  . . . . . . . . . . . . . . . . . . . . . 18
 9.3. REGISTER_RESPONSE . . . . . . . . . . . . . . . . . . . . . 19
 9.4. DE-REGISTER_REQUEST . . . . . . . . . . . . . . . . . . . . 19
 9.5. DE-REGISTER_RESPONSE  . . . . . . . . . . . . . . . . . . . 20
 9.6. ASSIGN_REQUEST_RSA-IP . . . . . . . . . . . . . . . . . . . 21
 9.7. ASSIGN_RESPONSE_RSA-IP  . . . . . . . . . . . . . . . . . . 22
 9.8. ASSIGN_REQUEST_RSAP-IP  . . . . . . . . . . . . . . . . . . 23
 9.9. ASSIGN_RESPONSE_RSAP-IP . . . . . . . . . . . . . . . . . . 26
 9.10. EXTEND_REQUEST . . . . . . . . . . . . . . . . . . . . . . 27
 9.11. EXTEND_RESPONSE  . . . . . . . . . . . . . . . . . . . . . 28
 9.12. FREE_REQUEST . . . . . . . . . . . . . . . . . . . . . . . 28
 9.13. FREE_RESPONSE  . . . . . . . . . . . . . . . . . . . . . . 29
 9.14. QUERY_REQUEST  . . . . . . . . . . . . . . . . . . . . . . 30
 9.15. QUERY_RESPONSE . . . . . . . . . . . . . . . . . . . . . . 31
 9.16. LISTEN_REQUEST . . . . . . . . . . . . . . . . . . . . . . 32
 9.17. LISTEN_RESPONSE  . . . . . . . . . . . . . . . . . . . . . 35
 10. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 36
 10.1. Use of Message Counters  . . . . . . . . . . . . . . . . . 36
 10.2. RSIP Host and Gateway Failure Scenarios  . . . . . . . . . 37
 10.3. General Gateway Policy . . . . . . . . . . . . . . . . . . 38
 10.4. Errors Not From the RSIP Protocol  . . . . . . . . . . . . 39

Borella, et al. Experimental [Page 2] RFC 3103 RSIP Protocol Specification October 2001

 10.5. Address and Port Requests and Allocation . . . . . . . . . 40
 10.6. Local Gateways and Flow Policy Interaction . . . . . . . . 40
 11. Security Considerations  . . . . . . . . . . . . . . . . . . 40
 12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . 41
 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 41
 14. Appendix A: RSIP Error Numbers . . . . . . . . . . . . . . . 42
 15. Appendix B: Message Types  . . . . . . . . . . . . . . . . . 44
 16. Appendix C: Example RSIP host/gateway transactions . . . . . 45
 17. Appendix D: Example RSIP host state diagram  . . . . . . . . 50
 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 52
 19. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 53
 20. Full Copyright Statement . . . . . . . . . . . . . . . . . . 54

1. Introduction

 Network Address Translation (NAT) has gained popularity as a method
 of separating public and private address spaces, and alleviating
 network address shortages.  A NAT translates the addresses of packets
 leaving a first routing realm to an address from a second routing
 realm, and performs the reverse function for packets entering the
 first routing realm from the second routing realm.  This translation
 is performed transparently to the hosts in either space, and may
 include modification of TCP/UDP port numbers and IP addresses in
 packets that traverse the NAT.
 While a NAT does not require hosts to be aware of the translation, it
 will require an application layer gateway (ALG) for any protocol that
 transmits IP addresses or port numbers in packet payloads (such as
 FTP).  Additionally, a NAT will not work with protocols that require
 IP addresses and ports to remain unmodified between the source and
 destination hosts, or protocols that prevent such modifications from
 occurring (such as some IPsec modes, or application-layer end-to-end
 encryption).
 An alternative to a NAT is an architecture that allows the hosts
 within the first (e.g., private) routing realm to directly use
 addresses and other routing parameters from the second (e.g., public)
 routing realm.  Thus, RSIP [RSIP-FRAME] has been defined as a method
 for address sharing that exhibits more transparency than NAT.  In
 particular, RSIP requires that an RSIP gateway (a router or gateway
 between the two realms) assign at least one address from the second
 routing realm, and perhaps some other resources, to each RSIP host.
 An RSIP host is a host in the first routing realm that needs to
 establish end-to-end connectivity to a host, entity or device in the
 second routing realm.  Thus, the second routing realm is not directly

Borella, et al. Experimental [Page 3] RFC 3103 RSIP Protocol Specification October 2001

 accessible from the RSIP host, but this system allows packets to
 maintain their integrity from the RSIP host to their destination.
 ALGs are not required in the RSIP gateway.
 RSIP requires that hosts be modified so that they place some number
 of layer three, layer four or other values from those assigned by the
 RSIP gateway in each packet bound for the second routing realm.
 This document discusses a method for assigning parameters to an RSIP
 host from an RSIP gateway.  The requirements, scope, and
 applicability of RSIP, as well as its interaction with other layer 3
 protocols, are discussed in a companion framework document [RSIP-
 FRAME].  Extensions to this protocol that enable end-to-end IPsec are
 discussed in [RSIP-IPSEC].

2. Specification of Requirements

 The keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
 "SHALL", "SHALL NOT", "MAY" and "MAY NOT" that appear in this
 document are to be interpreted as described in [RFC2119].

3. Terminology

 Private Realm
    A routing realm that uses private IP addresses from the ranges
    (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) specified in
    [RFC1918], or addresses that are non-routable from the Internet.
 Public Realm
    A routing realm with unique network addresses assigned by the
    Internet Assigned Number Authority (IANA) or an equivalent address
    registry.
 RSIP Host
    A host within the private realm that acquires publicly unique
    parameters from an RSIP gateway through the use of the RSIP
    client/server protocol.
 RSIP Gateway
    A router situated on the boundary between a private realm and a
    public realm and owns one or more public IP addresses.  An RSIP
    gateway is responsible for public parameter management and
    assignment to RSIP hosts.  An RSIP gateway may act as a NAT router
    for hosts within the private realm that are not RSIP enabled.

Borella, et al. Experimental [Page 4] RFC 3103 RSIP Protocol Specification October 2001

 RSIP Client
    An application program that performs the client portion of the
    RSIP client/server protocol.  An RSIP client application MUST
    exist on all RSIP hosts, and MAY exist on RSIP gateways.
 RSIP Server
    An application program that performs the server portion of the
    RSIP client/server protocol.  An RSIP server application MUST
    exist on all RSIP gateways.
 RSA-IP: Realm Specific Address IP
    An RSIP method in which each RSIP host is allocated a unique IP
    address from the public realm.  Discussed in detail in [RSIP-
    FRAME]
 RSAP-IP: Realm Specific Address and Port IP
    An RSIP method in which each RSIP host is allocated an IP address
    (possibly shared with other RSIP hosts) and some number of per-
    address unique ports from the public realm.  Discussed in detail
    in [RSIP-FRAME]
 Binding
    An association of some combination of a local address, one or more
    local ports, a remote address, and a remote port with an RSIP
    host.
 Resource
    A general way to refer to an item that an RSIP host leases from an
    RSIP gateway; e.g., an address or port.
 All other terminology found in this document is consistent with that
 of [RFC2663] and [RSIP-FRAME].

4. Architecture

 For simplicity, in the remainder of this document we will assume that
 the RSIP hosts in the first routing realm (network) use private
 (e.g., see [RFC1918]) IP addresses, and that the second routing realm
 (network) uses public IP addresses.  (This assumption is made without
 loss of generality and the ensuing discussion applies to more general

Borella, et al. Experimental [Page 5] RFC 3103 RSIP Protocol Specification October 2001

 cases.)  The RSIP gateway connects the public and private realms and
 contains interfaces to both.  Other NAT terminology found in this
 document is defined in [RFC2663].
 The diagram below describes an exemplary reference architecture for
 RSIP.
    RSIP Host             RSIP Gateway                    Host
       Xa                    Na   Nb                      Yb
    [X]------( Addr sp. A )----[N]-----( Addr sp. B )-------[Y]
             (  Network   )            (  Network   )
 Hosts X and Y belong to different addressing realms A and B,
 respectively, and N is an RSIP gateway (which may also perform NAT
 functions).  N has two interfaces: Na on address space A, and Nb on
 address space B.  N may have a pool of addresses in address space B
 which it can assign to or lend to X and other hosts in address space
 A.  These addresses are not shown above, but they can be denoted as
 Nb1, Nb2, Nb3 and so on.
 Host X, needing to establish an end-to-end connection to a network
 entity Y situated within address space B, first negotiates and
 obtains assignment of the resources from the RSIP gateway.  Upon
 assignment of these parameters, the RSIP gateway creates a mapping,
 of X's addressing information and the assigned resources.  This
 binding enables the RSIP gateway to correctly de-multiplex and
 forward inbound traffic generated by Y for X.  A lease time is
 associated with each bind.
 Using the public parameters assigned by the RSIP gateway, RSIP hosts
 tunnel data packets across address space A to the RSIP gateway.  The
 RSIP gateway acts as the end point of such tunnels, stripping off the
 outer headers and routing the inner packets onto the public realm.
 As mentioned above, an RSIP gateway maintains a mapping of the
 assigned public parameters as demultiplexing fields for uniquely
 mapping them to RSIP host private addresses.  When a packet from the
 public realm arrives at the RSIP gateway and it matches a given set
 of demultiplexing fields, then the RSIP gateway will tunnel it to the
 appropriate RSIP host.  The tunnel headers of outbound packets from X
 to Y, given that X has been assigned Nb, are as follows:
          +---------+---------+---------+
          | X -> Na | Nb -> Y | payload |
          +---------+---------+---------+

Borella, et al. Experimental [Page 6] RFC 3103 RSIP Protocol Specification October 2001

 There are two basic flavors of RSIP: RSA-IP and RSAP-IP.  RSIP hosts
 and gateways MUST support RSAP-IP and MAY support RSA-IP.  Details of
 RSA-IP and RSAP-IP are found in [RSIP-FRAME].

5. Transport Protocol

 RSIP is an application layer protocol that requires the use of a
 transport layer protocol for end-to-end delivery of packets.
 RSIP gateways MUST support TCP, and SHOULD support UDP.  Due to the
 fact that RSIP may be deployed across a wide variety of network
 links, RSIP hosts SHOULD support TCP, because of TCP's robustness
 across said variety of links.  However, RSIP hosts MAY support UDP
 instead of TCP, or both UDP and TCP.
 For RSIP hosts and gateways using UDP, timeout and retransmissions
 MUST occur.  We recommend a binary exponential backoff scheme with an
 initial duration of 12.5 ms, and a maximum of six retries (seven
 total attempts before failure).  However, these parameters MAY be
 adjusted or tuned for specific link types or scenarios.
 Once a host and gateway have established a registration using either
 TCP or UDP, they may not switch between the two protocols for the
 duration of the registration.  The decision of whether to use TCP or
 UDP is made by the client, and is determined by the transport
 protocol of the first packet sent by a client in a successful
 registration procedure.

6. Host / Gateway Relationships

 An RSIP host can be in exactly one of three fundamental relationships
 with respect to an RSIP gateway:
 Unregistered: The RSIP gateway does not know of the RSIP host's
    existence, and it will not forward or deliver globally addressed
    packets on behalf of the host.  The only valid RSIP-related action
    for an RSIP host to perform in this state is to request
    registration with an RSIP gateway.
 Registered: The RSIP gateway knows of the RSIP host and has assigned
    it a client ID and has specified the flow policies that it
    requires of the host.  However, no resources, such as addresses or
    ports, have been allocated to the host, and the gateway will not
    forward or deliver globally addressed packets on behalf of the
    host.  All registrations have an associated lease time.  If this
    lease time expires, the RSIP host automatically reverts to the
    unregistered state.

Borella, et al. Experimental [Page 7] RFC 3103 RSIP Protocol Specification October 2001

 Assigned: The RSIP gateway has granted one or more bindings of
    resources to the host.  The gateway will forward and deliver
    globally addressed packets on behalf of the host.  Each binding
    has an associated lease time.  If this lease time expires, the
    binding is automatically revoked.
 Architectures in which an RSIP host is simultaneously registered with
 more than one RSIP gateway are possible.  In such cases, an RSIP host
 may be in different relationships with different RSIP gateways at the
 same time.
 An RSIP gateway MAY redirect an RSIP host to use a tunnel endpoint
 for data traffic that is not the RSIP gateway itself, or perhaps is a
 different interface on the RSIP gateway.  This is done by specifying
 the tunnel endpoint's address as part of an assignment.  In such an
 architecture, it is desirable (though not necessary) for the RSIP
 gateway to have a method with which to notify the tunnel endpoint of
 assignments, and the expiration status of these assignments.
 Lease times for bindings and registrations are managed as follows.
 All lease times are given in units of seconds from the current time,
 indicating a time in the future at which the lease will expire.
 These expiration times are used in the ensuing discussion.
 An initial expiration time (R) is given to a registration.  Under
 this registration, multiple bindings may be established, each with
 their own expiration times (B1, B2, ...).  When each binding is
 established or extended, the registration expiration time is adjusted
 so that the registration will last at least as long as the longest
 lease.  In other words, when binding Bi is established or extended,
 the following calculation is performed: R = max(R, Bi).
 Under this scheme, a registration will never expire while any
 binding's lease is still valid.  However, a registration may expire
 when the last binding's lease expires, or at some point thereafter.

7. Gateway Flow Policy and State

 Since an RSIP gateway is likely to reside on the boundary between two
 or more different administrative domains, it is desirable to enable
 an RSIP gateway to be able to enforce flow-based policy.  In other
 words, an RSIP gateway should have the ability to explicitly control
 which local addresses and ports are used to communicate with remote
 addresses and ports.
 In the following, macro-flow policy refers to controlling flow policy
 at the granularity level of IP addresses, while micro-flow policy
 refers to controlling flow policy at the granularity of IP address

Borella, et al. Experimental [Page 8] RFC 3103 RSIP Protocol Specification October 2001

 and port tuples.  Of course there may be no policy at all, which
 indicates that the RSIP gateway does not care about the flow
 parameters used by RSIP hosts.  We consider two levels of local flow
 policy and three levels of remote flow policy.

7.1. Local Flow Policy

 Local flow policy determines the granularity of control that an RSIP
 gateway has over the local addressing parameters that an RSIP host
 uses for particular sessions.
 Since an RSIP host must use at least an IP address allocated by the
 gateway, the loosest level of local flow policy is macro-flow based.
 Under local macro-flow policy, an RSIP host is allocated an IP
 address (RSA-IP) or an IP address and one or more ports to use with
 it (RSAP-IP).  However, the host may use the ports as it desires for
 establishing sessions with public hosts.
 Under micro-flow policy, a host is allocated exactly one port at a
 time.  The host may request more ports, also one at a time.  This
 policy gives the gateway very tight control over local port use,
 although it affords the host less flexibility.
 Note that only local macro-flow policy can be used with RSA-IP, while
 either local macro-flow or local micro-flow policy may be used with
 RSAP-IP.
 Examples of how RSIP flow policy operates are given in Appendix C.

7.2. Remote Flow Policy

 Remote flow policy determines the granularity of control that an RSIP
 gateway has over the remote (public) hosts with which an RSIP host
 communicates.  In particular, remote flow policy dictates what level
 of detail that a host must specify addressing parameters of a remote
 host or application before the RSIP gateway allows the host to
 communicate with that host or application.
 The simplest and loosest form of flow policy is no policy at all.  In
 other words, the RSIP gateway allocates addressing parameters to the
 host, and the host may use these parameters to communicate with any
 remote host, without explicitly notifying the gateway.
 Macro-flow policy requires that the host identify the remote address
 of the host that it wishes to communicate with as part of its request
 for local addressing parameters.  If the request is granted, the host
 MUST use the specified local parameters only with the remote address
 specified, and MUST NOT communicate with the remote address using any

Borella, et al. Experimental [Page 9] RFC 3103 RSIP Protocol Specification October 2001

 local parameters but the ones allocated.  However, the host may
 contact any port number at the remote host without explicitly
 notifying the gateway.
 Micro-flow policy requires that the host identify the remote address
 and port of the host that it wishes to communicate with as part of
 its request for local addressing parameters.  If the request is
 granted, the host MUST use the specified local parameters only with
 the remote address and port specified, and MUST NOT communicate with
 the remote address and port using any local parameters but the ones
 allocated.
 Remote flow policy is implemented in both the ingress and egress
 directions, with respect to the location of the RSIP gateway.

7.3. Gateway State

 An RSIP gateway must maintain state for all RSIP hosts and their
 assigned resources.  The amount and type of state maintained depends
 on the local and remote flow policy.  The required RSIP gateway state
 will vary based on the RSIP method, but will always include the
 chosen method's demultiplexing parameters.

7.3.1. RSA-IP State

 An RSIP gateway serving an RSIP host using the RSA-IP method MUST
 maintain the following minimum state to ensure proper mapping of
 incoming packets to RSIP hosts:
  1. Host's private address
  2. Host's assigned public address(es)

7.3.2. RSAP-IP State

 An RSIP gateway serving an RSIP host using the RSAP-IP method MUST
 maintain the following minimum state to ensure proper mapping of
 incoming packets to RSIP hosts:
  1. Host's private address
  2. Host's assigned public address(es)
  3. Host's assigned port(s) per address

7.3.3. Flow State

 Regardless of whether the gateway is using RSA-IP or RSAP-IP,
 additional state is necessary if either micro-flow based or macro-
 flow based remote policy is used.

Borella, et al. Experimental [Page 10] RFC 3103 RSIP Protocol Specification October 2001

 If the gateway is using macro-flow based remote policy, the following
 state must be maintained:
  1. Remote host's address
 If the gateway is using micro-flow based remote policy, the following
 state must be maintained:
  1. Remote host's address
  2. Remote host's port
 More state MAY be used by an RSIP gateway if desired.  For example,
 ToS/DS bytes may be recorded in order to facilitate quality of
 service support.

8. Parameter Specification and Formats

 In this section we define the formats for RSIP parameters.  Each RSIP
 message contains one or more parameters that encode the information
 passed between the host and gateway.  The general format of all
 parameters is TLV (type-length-value) consisting of a 1-byte type
 followed by a 2-byte length followed by a 'length' byte value as
 shown below.
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Type      |            Length             |     Value     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   Value ...
 +-+-+-+-+-+-+-+-+-+-+-+
 The value field may be divided into a number of other fields as per
 the type of the parameter.  Note that the length field encodes the
 number of bytes in the value field, NOT the overall number of bytes
 in the parameter.

8.1. Address

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 1   |            Length             |    Addrtype   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   Address...
 +-+-+-+-+-+-+-+-+-+-+-+

Borella, et al. Experimental [Page 11] RFC 3103 RSIP Protocol Specification October 2001

 The address parameter contains addressing information, either an IPv4
 address or netmask, an IPv6 address or netmask, or a fully qualified
 domain name (FQDN).  The Addrtype field is 1 byte in length,
 indicating the type of address.
           Addrtype       Length of address field (in bytes)
           ----           --------------------------------
    0      Reserved       0
    1      IPv4           4
    2      IPv4 netmask   4
    3      IPv6           16
    4      FQDN           varies
 For FQDN (Fully qualified domain name), the length of the address
 field will be one less than the value of the length field, and the
 name will be represented as an ASCII string (no terminating
 character).
 In some cases, it is necessary to specify a "don't care" value for an
 address.  This is signified by a setting the length field to 1 and
 omitting the value field.
 It is not valid for a host to request an address with an FQDN type as
 its local address (See specification of ASSIGN_REQUEST_RSA-IP and
 ASSIGN_REQUEST_RSAP-IP, below).

8.2. Ports

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 2   |            Length             |     Number    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |           Port number         |  ...
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The ports parameter encodes zero or more TCP or UDP ports.  When a
 single port is specified, the value of the number field is 1 and
 there is one port field following the number field.  When more than
 one port is specified, the value of the number field will indicate
 the total number of ports contained, and the parameter may take one
 of two forms.  If there is one port field, the ports specified are
 considered to be contiguous starting at the port number specified in
 the port field.  Alternatively, there may be a number of port fields
 equal to the value of the number field.  The number of port fields
 can be extrapolated from the length field.

Borella, et al. Experimental [Page 12] RFC 3103 RSIP Protocol Specification October 2001

 In some cases, it is necessary to specify a don't care value for one
 or more ports (e.g., when a client application is using ephemeral
 source ports).  This is accomplished by setting the length field to
 1, setting the number field to the number of ports necessary, and
 omitting all port fields.  The value of the number field MUST be
 greater than or equal to one.
 If micro-flow based policy applies to a given ports parameter, it
 MUST contain exactly one port field.

8.3. Lease Time

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 3   |          Length = 4           |   Lease time  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Lease time                  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The lease time parameter specifies the length, in seconds, of an
 RSIP host registration or parameter binding.

8.4. Client ID

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 4   |          Length = 4           |   Client ID   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                    Client ID                  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The client ID parameter specifies an RSIP client ID.  Client ID's
 by an RSIP gateway to differentiate RSIP hosts.

8.5. Bind ID

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 5   |          Length = 4           |    Bind ID    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Bind ID                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The bind ID parameter specifies an RSIP bind ID.  Bind ID's are used
 by RSIP hosts and gateways to differentiate an RSIP host's bindings.

Borella, et al. Experimental [Page 13] RFC 3103 RSIP Protocol Specification October 2001

8.6. Tunnel Type

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 6   |          Length = 1           |  Tunnel type  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The tunnel type parameter specifies the type of tunnel used between
 an RSIP host and an RSIP gateway.  Defined tunnel types are:
           Tunnel Type
           -----------
    0      Reserved
    1      IP-IP
    2      GRE
    3      L2TP

8.7. RSIP Method

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 7   |          Length = 1           |  RSIP method  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The RSIP method parameter specifies an RSIP method.  Defined RSIP
 methods are:
           RSIP method
           -----------
    0      Reserved
    1      RSA-IP
    2      RSAP-IP

8.8. Error

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 8   |          Length = 2           |     Error     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Error     |
 +-+-+-+-+-+-+-+-+
 The error parameter specifies an error.  The currently defined error
 values are presented in Appendix A.

Borella, et al. Experimental [Page 14] RFC 3103 RSIP Protocol Specification October 2001

8.9. Flow Policy

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 9   |          Length = 2           |     Local     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Remote     |
 +-+-+-+-+-+-+-+-+
 The flow policy parameter specifies both the local and remote flow
 policy.
 Defined local flow policies are:
           Local Flow Policy
           -----------------
    0      Reserved
    1      Macro flows
    2      Micro flows
 Defined remote flow policies are:
           Remote Flow Policy
           ------------------
    0      Reserved
    1      Macro flows
    2      Micro flows
    3      No policy

8.10. Indicator

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 10  |          Length = 2           |     Value     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Value     |
 +-+-+-+-+-+-+-+-+
 An indicator parameter is a general-purpose parameter, the use of
 which is defined by the message that it appears in.  An RSIP message
 that uses an indicator parameter MUST define the meaning and
 interpretation of all of the indicator's possible values.

Borella, et al. Experimental [Page 15] RFC 3103 RSIP Protocol Specification October 2001

8.11. Message Counter

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 11  |          Length = 4           |     Counter   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                    Counter                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 A message counter parameter is used to mark RSIP messages with
 sequentially-increasing values.  Message counters MUST be used with
 UDP, in order to facilitate reliability.

8.12. Vendor Specific Parameter

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = 12  |            Length             |    Vendor ID  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Vendor ID  |            Subtype            |    Value...
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The vendor specific parameter is used to encode parameters that are
 defined by a particular vendor.  The vendor ID field is the vendor-
 specific ID assigned by IANA.  Subtypes are defined and used by each
 vendor as necessary.  An RSIP host or gateway SHOULD silently ignore
 vendor-specific messages that it does not understand.

9. Message Types

 RSIP messages consist of three mandatory fields, version, message
 type, and overall length, followed by one or more required
 parameters, followed in turn by zero or more optional parameters.  In
 an RSIP message, all required parameters MUST appear in the exact
 order specified below.  Optional parameters MAY appear in any order.
 Message format is shown below:
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Version    |  Message type |         Overall length        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Parameters...
 +-+-+-+-+-+-+-+-+-+-+

Borella, et al. Experimental [Page 16] RFC 3103 RSIP Protocol Specification October 2001

 The version number field is a single byte and specifies the RSIP
 version number that is being used.  The current RSIP version number
 is 1.
 The message type field is a single byte and specifies the message
 contained in the current packet.  There may be only one message per
 packet.  Message types are given numerical assignments in Appendix B.
 The overall length field is two bytes and contains the number of
 bytes in the RSIP message, including the three mandatory fields.
 Most parameters are only allowed to appear once in each message.  The
 exceptions are as follows:
  1. Multiple address parameters MUST appear in ASSIGN_REQUEST_RSA-

IP, ASSIGN_RESPONSE_RSA-IP, ASSIGN_REQUEST_RSAP-IP,

       ASSIGN_RESPONSE_RSAP-IP, LISTEN_REQUEST and LISTEN_RESPONSE.
  1. Multiple ports parameters MUST appear in ASSIGN_REQUEST_RSAP-

IP, ASSIGN_RESPONSE_RSAP-IP, LISTEN_REQUEST and

       LISTEN_RESPONSE.
  1. Multiple RSIP method and tunnel type parameters MAY appear in

RESISTER_RESPONSE.

  1. Multiple address parameters and multiple indicator parameters

MAY appear in QUERY_REQUEST and QUERY_RESPONSE.

 The following message types are defined in BNF.  Required parameters
 are enclosed in <> and MUST appear.  Optional parameters are enclosed
 in [] and MAY appear.  Not all message types need to be implemented
 in order to be RSIP compliant.  For example, an RSIP host and/or
 gateway may not support LISTEN_REQUEST and LISTEN_RESPONSE, or may
 only support RSAP-IP and not RSA-IP.

9.1. ERROR_RESPONSE

9.1.1. Description

 An ERROR_RESPONSE is used to provide error messages from an RSIP
 gateway to an RSIP host.  Usually, errors indicate that the RSIP
 gateway cannot or will not perform an action or allocate resources on
 behalf of the host.  If the error is related to a particular client
 ID or bind ID, these associated parameters MUST be included.
 Multiple errors MAY NOT be reported in the same ERROR_RESPONSE.  In
 situations where more than one error has occurred, the RSIP gateway
 MUST choose only one error to report.

Borella, et al. Experimental [Page 17] RFC 3103 RSIP Protocol Specification October 2001

9.1.2. Format

 <ERROR_RESPONSE> ::= <Version>
                      <Message Type>
                      <Overall Length>
                      <Error>
                      [Message Counter]
                      [Client ID]
                      [Bind ID]

9.1.3. Behavior

 An ERROR_RESPONSE message MUST only be transmitted by an RSIP
 gateway.  An RSIP host that detects an error in a message received
 from an RSIP gateway MUST silently discard the message.  There are no
 error conditions that can be caused by an ERROR_RESPONSE.  An
 ERROR_RESPONSE is typically transmitted in response to a request from
 an RSIP host, but also may be transmitted asynchronously by an RSIP
 gateway.

9.2. REGISTER_REQUEST

9.2.1. Description

 The REGISTER_REQUEST message is used by an RSIP host to establish
 registration with an RSIP gateway.  An RSIP host MUST register before
 it requests resources or services from an RSIP gateway.  Once an RSIP
 host has registered with an RSIP gateway, it may not register again
 until it has de-registered from that gateway.

9.2.2. Format

 <REGISTER_REQUEST> ::= <Version>
                        <Message Type>
                        <Overall Length>
                        [Message Counter]

9.2.3. Behavior

 The following message-specific error conditions exist:
  1. If the host is already registered with the gateway, the gateway

MUST respond with an ERROR_RESPONSE containing the

       ALREADY_REGISTERED error and the RSIP host's client ID.
  1. If the gateway's policy will not allow the host to register,

the gateway MUST respond with an ERROR_RESPONSE containing the

       REGISTRATION_DENIED error.

Borella, et al. Experimental [Page 18] RFC 3103 RSIP Protocol Specification October 2001

9.3. REGISTER_RESPONSE

9.3.1. Description

 The REGISTER_RESPONSE message is used by an RSIP gateway to confirm
 the registration of an RSIP host, and to provide a client ID, flow
 policy, and possibly a message counter and one or more RSIP methods
 and/or tunnel types.

9.3.2. Format

 <REGISTER_RESPONSE> ::= <Version>
                         <Message Type>
                         <Overall Length>
                         <Client ID>
                         <Lease time>
                         <Flow Policy>
                         [Message Counter]
                         [RSIP Method]...
                         [Tunnel Type]...

9.3.3. Behavior

 An RSIP gateway MUST assign a different client ID to each host that
 is simultaneously registered with it.  The RSIP gateway MAY respond
 with one or more RSIP methods and tunnel types that it supports.  If
 an RSIP method is not specified, RSAP-IP MUST be assumed.  If a
 tunnel type is not specified, IP-IP MUST be assumed.

9.4. DE-REGISTER_REQUEST

9.4.1. Description

 The DE-REGISTER_REQUEST message is used by an RSIP host to de-
 register with an RSIP gateway.  If a host de-registers from the
 assigned state, all of the host's bindings are revoked.  The host
 SHOULD NOT de-register from the unregistered state.

9.4.2. Format

 <DE-REGISTER_REQUEST> ::= <Version>
                           <Message Type>
                           <Overall Length>
                           <Client ID>
                           [Message Counter]

Borella, et al. Experimental [Page 19] RFC 3103 RSIP Protocol Specification October 2001

9.4.3. Behavior

 The following message-specific error conditions exist:
  1. If the host is not registered with the gateway, the gateway

MUST respond with an ERROR_RESPONSE containing the

       REGISTER_FIRST error.
  1. If the message contains an incorrect client ID, the gateway

MUST respond with an ERROR_RESPONSE containing the

       BAD_CLIENT_ID error.
 If there are no errors that result from this message, the gateway
 MUST respond with an appropriate DE-REGISTER_RESPONSE.  Upon de-
 registering a host, an RSIP gateway must delete all binds associated
 with that host and return their resources to the pool of free
 resources.  Once a host has de-registered, it may not use any of the
 RSIP gateway's resources without registering again.

9.5. DE-REGISTER_RESPONSE

9.5.1. Description

 The DE-REGISTER_RESPONSE message is used by an RSIP gateway to
 confirm the de-registration of an RSIP host or to force an RSIP host
 to relinquish all of its bindings and terminate its relationship with
 the RSIP gateway.  Upon receiving a DE-REGISTER_RESPONSE message, an
 RSIP host MUST stop all use of the resources that have been allocated
 to it by the gateway.

9.5.2. Format

 <DE-REGISTER_RESPONSE> ::= <Version>
                            <Message Type>
                            <Overall Length>
                            <Client ID>
                            [Message Counter]

9.5.3. Behavior

 An RSIP gateway MUST send a DE-REGISTER_RESPONSE in response to a
 valid DE-REGISTER_REQUEST.  An RSIP gateway MUST send a DE-
 REGISTER_RESPONSE to an RSIP host when that host's registration lease
 time times out.  An RSIP gateway SHOULD send a DE-REGISTER_RESPONSE
 if it detects that it will no longer be able to perform RSIP
 functionality for a given host.  An RSIP host MUST be ready to accept
 a DE-REGISTER_RESPONSE at any moment.

Borella, et al. Experimental [Page 20] RFC 3103 RSIP Protocol Specification October 2001

9.6. ASSIGN_REQUEST_RSA-IP

9.6.1. Description

 The ASSIGN_REQUEST_RSA-IP message is used by an RSIP host to request
 resources to use with RSA-IP.  Note that RSA-IP cannot be used in
 combination with micro-flow based local policy.

9.6.2. Format

 <ASSIGN_REQUEST_RSA-IP> ::= <Version>
                             <Message Type>
                             <Overall Length>
                             <Client ID>
                             <Address (local)>
                             <Address (remote)>
                             <Ports (remote)>
                             [Message Counter]
                             [Lease Time]
                             [Tunnel Type]

9.6.3. Behavior

 The RSIP host specifies two address parameters.  The RSIP host may
 request a particular local address by placing that address in the
 first address parameter.  To indicate that it has no preference for
 local address, the RSIP host may place a "don't care" value in the
 address parameter.
 If macro-flow based remote policy is used, the host MUST specify the
 remote address that it will use this binding (if granted) to contact;
 however, the remote port number MAY remain unspecified.  If micro-
 flow based remote policy is used, the host MUST specify the remote
 address and port number that it will use this binding (if granted) to
 contact.  If no flow policy is used, the RSIP host may place a "don't
 care" value in the value fields of the respective address and ports
 parameters.
 The following message-specific error conditions exist:
  1. If the host is not registered with the gateway, the gateway

MUST respond with an ERROR_RESPONSE containing the

       REGISTER_FIRST error.
  1. If the message contains an incorrect client ID, the gateway

MUST respond with an ERROR_RESPONSE containing the

       BAD_CLIENT_ID error.

Borella, et al. Experimental [Page 21] RFC 3103 RSIP Protocol Specification October 2001

  1. If the local address parameter is a don't care value and the

RSIP gateway cannot allocate ANY addresses, the RSIP gateway

       MUST respond with an ERROR_RESPONSE containing the
       LOCAL_ADDR_UNAVAILABLE error.
  1. If the local address parameter is not a don't care value there

are three possible error conditions:

       o  If the RSIP gateway cannot allocate ANY addresses, it MUST
          respond with an ERROR_RESPONSE containing the
          LOCAL_ADDR_UNAVAILABLE error.
       o  If the RSIP gateway cannot allocate the requested address
          because it is in use, the RSIP gateway MUST respond with an
          ERROR_RESPONSE containing the LOCAL_ADDR_INUSE error.
       o  If the RSIP gateway cannot allocate the requested address
          because it is not allowed by policy, the RSIP gateway MUST
          respond with an ERROR_RESPONSE containing the
          LOCAL_ADDR_UNALLOWED error.
  1. If macro-flow based remote policy is used and the requested

remote address is not allowed by the RSIP gateway's policy, the

       RSIP gateway MUST respond with an ERROR_RESPONSE containing the
       REMOTE_ADDR_UNALLOWED error.
  1. If micro-flow based remote policy is used and the requested

remote address / port pair is not allowed by the RSIP gateway's

       policy, the RSIP gateway MUST respond with an ERROR_RESPONSE
       containing the REMOTE_ADDRPORT_UNALLOWED error.
  1. If an unsupported or unallowed tunnel type is specified, the

RSIP gateway MUST respond with an ERROR_RESPONSE containing the

       BAD_TUNNEL_TYPE error.
  1. If the host has not specified local or remote address or port

information in enough detail, the RSIP gateway MUST respond

       with an ERROR_RESPONSE containing the FLOW_POLICY_VIOLATION
       error.

9.7. ASSIGN_RESPONSE_RSA-IP

9.7.1. Description

 The ASSIGN_RESPONSE_RSA-IP message is used by an RSIP gateway to
 deliver parameter assignments to an RSIP host using RSA-IP.  A host-
 wise unique bind ID, lease time, and tunnel type must be provided for
 every assignment.

Borella, et al. Experimental [Page 22] RFC 3103 RSIP Protocol Specification October 2001

9.7.2. Format

 <ASSIGN_RESPONSE_RSA-IP> ::= <Version>
                              <Message Type>
                              <Overall Length>
                              <Client ID>
                              <Bind ID>
                              <Address (local)>
                              <Address (remote)>
                              <Ports (remote)>
                              <Lease Time>
                              <Tunnel Type>
                              [Address (tunnel endpoint)]
                              [Message Counter]

9.7.3. Behavior

 If no remote flow policy is used, the RSIP gateway MUST use "don't
 care" values for the remote address and ports parameters.  If macro-
 flow based remote policy is used, the remote address parameter MUST
 contain the address specified in the associated request, and the
 remote ports parameter MUST contain a "don't care" value.  If micro-
 flow based remote policy is used, the remote address and remote ports
 parameters MUST contain the address and port information specified in
 the associated request.
 If the host detects an error or otherwise does not "understand" the
 gateway's response, it SHOULD send a FREE_REQUEST with the bind ID
 from the said ASSIGN_RESPONSE_RSA-IP.  This will serve to help
 synchronize the states of the host and gateway.
 The address of a tunnel endpoint that is not the RSIP gateway MAY be
 specified.  If this parameter is not specified, the RSIP gateway MUST
 be assumed to be the tunnel endpoint.

9.8. ASSIGN_REQUEST_RSAP-IP

9.8.1. Description

 The ASSIGN_REQUEST_RSAP-IP message is used by an RSIP host to request
 resources to use with RSAP-IP.  The RSIP host specifies two address
 and two port parameters, the first of each, respectively, refer to
 the local address and port(s) that will be used, and the second of
 each, respectively, refer to the remote address and port(s) that will
 be contacted.

Borella, et al. Experimental [Page 23] RFC 3103 RSIP Protocol Specification October 2001

9.8.2. Format

 <ASSIGN_REQUEST_RSAP-IP> ::= <Version>
                              <Message Type>
                              <Overall Length>
                              <Client ID>
                              <Address (local)>
                              <Ports (local)>
                              <Address (remote)>
                              <Ports (remote)>
                              [Message Counter]
                              [Lease Time]
                              [Tunnel Type]

9.8.3. Behavior

 An RSIP host may request a particular local address by placing that
 address in the value field of the first address parameter.  The RSIP
 host may request particular local ports by placing them in the first
 port parameter.  To indicate that it has no preference for local
 address or ports, the RSIP host may place a "don't care" value in the
 respective address or ports parameters.
 If macro-flow based remote policy is used, the host MUST specify the
 remote address that it will use this binding (if granted) to contact;
 however, the remote port number(s) MAY remain unspecified.  If
 micro-flow based remote policy is used, the host MUST specify the
 remote address and port number(s) that it will use this binding (if
 granted) to contact.  If no flow policy is used, the RSIP host may
 place a value of all 0's in the value fields of the respective
 address or port parameters.
 The following message-specific error conditions exist:
  1. If the host is not registered with the gateway, the gateway

MUST respond with an ERROR_RESPONSE containing the

       REGISTER_FIRST error.
  1. If the message contains an incorrect client ID, the gateway

MUST respond with an ERROR_RESPONSE containing the

       BAD_CLIENT_ID error.
  1. If the local address parameter is a don't care value and the

RSIP gateway cannot allocate ANY addresses, the RSIP gateway

       MUST respond with an ERROR_RESPONSE containing the
       LOCAL_ADDR_UNAVAILABLE error.

Borella, et al. Experimental [Page 24] RFC 3103 RSIP Protocol Specification October 2001

  1. If the local address parameter is not a don't care value there

are five possible error conditions:

       o  If the RSIP gateway cannot allocate ANY addresses, it MUST
          respond with an ERROR_RESPONSE containing the
          LOCAL_ADDR_UNAVAILABLE error.
       o  If the RSIP gateway cannot allocate the requested address
          because it is in use, the RSIP gateway MUST respond with an
          ERROR_RESPONSE containing the LOCAL_ADDR_INUSE error.
       o  If the RSIP gateway cannot allocate the requested address
          because it is not allowed by policy, the RSIP gateway MUST
          respond with an ERROR_RESPONSE containing the
          LOCAL_ADDR_UNALLOWED error.
       o  If the RSIP gateway cannot allocate a requested address /
          port tuple because it is in use, the RSIP gateway MUST
          respond with an ERROR_RESPONSE containing the
          LOCAL_ADDRPORT_INUSE error.
       o  If the RSIP gateway cannot allocate a requested address /
          port tuple because it is not allowed by policy, the RSIP
          gateway MUST respond with an ERROR_RESPONSE containing the
          LOCAL_ADDRPORT_UNALLOWED error.
  1. If the RSIP host requests a number of ports (greater that one),

but does not specify particular port numbers (i.e., uses "don't

       care" values) the RSIP gateway cannot grant the entire request,
       the RSIP gateway MUST return an ERROR_RESPONSE containing the
       LOCAL_ADDRPORT_UNAVAILABLE error.
  1. If macro-flow based remote policy is used and the requested

remote address is not allowed by the RSIP gateway's policy, the

       RSIP gateway MUST respond with an ERROR_RESPONSE containing the
       REMOTE_ADDR_UNALLOWED error.
  1. If micro-flow based remote policy is used and the requested

remote address / port pair is not allowed by the RSIP gateway's

       policy, the RSIP gateway MUST respond with an ERROR_RESPONSE
       containing the REMOTE_ADDRPORT_UNALLOWED error.
  1. If an unsupported or unallowed tunnel type is specified, the

RSIP gateway MUST respond with an ERROR_RESPONSE containing the

       BAD_TUNNEL_TYPE error.

Borella, et al. Experimental [Page 25] RFC 3103 RSIP Protocol Specification October 2001

  1. If the host has not specified local or remote address or port

information in enough detail, the RSIP gateway MUST respond

       with an ERROR_RESPONSE containing the FLOW_POLICY_VIOLATION
       error.

9.9. ASSIGN_RESPONSE_RSAP-IP

9.9.1. Description

 The ASSIGN_RESPONSE_RSAP-IP message is used by an RSIP gateway to
 deliver parameter assignments to an RSIP host.  A host-wise unique
 bind ID, lease time, and tunnel type must be provided for every
 assignment.

9.9.2. Format

 <ASSIGN_RESPONSE_RSAP-IP> ::= <Version>
                               <Message Type>
                               <Overall Length>
                               <Client ID>
                               <Bind ID>
                               <Address (local)>
                               <Ports (local)>
                               <Address (remote)>
                               <Ports (remote)>
                               <Lease Time>
                               <Tunnel Type>
                               [Address (tunnel endpoint)]
                               [Message Counter]

9.9.3. Behavior

 Regardless of local flow policy, a local address and port(s) MUST be
 assigned to the host.  If macro-flow based local policy is used, the
 host is assigned an address and one or more ports.  If micro-flow
 based local policy is used, the host is assigned an address and
 exactly one port.
 If no remote flow policy is used, the RSIP gateway MUST use "don't
 care" values for the remote address and ports parameters.  If macro-
 flow based remote policy is used, the remote address parameter MUST
 contain the address specified in the associated request, and the
 remote ports parameter must contain a "don't care" value.  If micro-
 flow based remote policy is used, the remote address and remote ports
 parameters MUST contain the address and port information specified in
 the associated request.

Borella, et al. Experimental [Page 26] RFC 3103 RSIP Protocol Specification October 2001

 If the host detects an error or otherwise does not "understand" the
 gateway's response, it SHOULD send a FREE_REQUEST with the bind ID
 from the said ASSIGN_RESPONSE_RSAP-IP.  This will serve to help
 synchronize the states of the host and gateway.
 The address of a tunnel endpoint that is not the RSIP gateway MAY be
 specified.  If this parameter is not specified, the RSIP gateway MUST
 be assumed to be the tunnel endpoint.

9.10. EXTEND_REQUEST

9.10.1. Description

 The EXTEND_REQUEST message is used to request a lease extension to a
 current bind.  It may be used with both RSA-IP and RSAP-IP.  The host
 MUST specify its client ID and the bind ID in question, and it MAY
 suggest a lease time to the gateway.

9.10.2. Format

 <EXTEND_REQUEST> ::= <Version>
                      <Message Type>
                      <Overall Length>
                      <Client ID>
                      <Bind ID>
                      [Lease Time]
                      [Message Counter]

9.10.3. Behavior

 The following message-specific error conditions exist:
  1. If the host is not registered with the gateway, the gateway

MUST respond with an ERROR_RESPONSE containing the

       REGISTER_FIRST error.
  1. If the message contains an incorrect client ID, the gateway

MUST respond with an ERROR_RESPONSE containing the

       BAD_CLIENT_ID error.
  1. If the message contains an incorrect bind ID, the gateway MUST

respond with an ERROR_RESPONSE containing the BAD_BIND_ID

       error.

Borella, et al. Experimental [Page 27] RFC 3103 RSIP Protocol Specification October 2001

 If the RSIP gateway grants an extension to the host's lease, it MUST
 RESPOND with an appropriate EXTEND_RESPONSE message.  If the lease is
 not renewed, the RSIP gateway MAY let it implicitly expire by doing
 nothing or make it explicitly expire by sending an appropriate
 FREE_RESPONSE message.

9.11. EXTEND_RESPONSE

9.11.1. Description

 The EXTEND_RESPONSE message is used by an RSIP gateway to grant a
 requested lease extension.  The gateway MUST specify the client ID of
 the host, the bind ID in question, and the new assigned lease time.

9.11.2. Format

 <EXTEND_RESPONSE> ::= <Version>
                       <Message Type>
                       <Overall Length>
                       <Client ID>
                       <Bind ID>
                       <Lease Time>
                       [Message Counter]

9.11.3. Behavior

 The RSIP gateway will determine lease time as per its local policy.
 The returned time is to be interpreted as the number of seconds
 before the lease expires, counting from the time at which the message
 is sent/received.

9.12. FREE_REQUEST

9.12.1. Description

 The FREE_REQUEST message is used by an RSIP host to free a binding.
 The given bind ID identifies the bind to be freed.  Resources may
 only be freed using the granularity of a bind ID.

9.12.2. Format

 <FREE_REQUEST> ::= <Version>
                    <Message Type>
                    <Overall Length>
                    <Client ID>
                    <Bind ID>
                    [Message Counter]

Borella, et al. Experimental [Page 28] RFC 3103 RSIP Protocol Specification October 2001

9.12.3. Behavior

 The following message-specific error conditions exist:
  1. If the host is not registered with the gateway, the gateway

MUST respond with an ERROR_RESPONSE containing the

       REGISTER_FIRST error.
  1. If the message contains an incorrect client ID, the gateway

MUST respond with an ERROR_RESPONSE containing the

       BAD_CLIENT_ID error.
  1. If the message contains an incorrect bind ID, the gateway MUST

respond with an ERROR_RESPONSE containing the BAD_BIND_ID

       error.
 If a host receives an error in response to a FREE_REQUEST, this may
 indicate that the host and gateway's states have become
 unsynchronized.  Therefore, the host SHOULD make an effort to
 resynchronize, such as freeing resources then re-requesting them, or
 de-registering then re-registering.

9.13. FREE_RESPONSE

9.13.1. Description

 The FREE_RESPONSE message is used by an RSIP gateway to acknowledge a
 FREE_REQUEST sent by an RSIP host, and to asynchronously deallocate
 resources granted to an RSIP host.

9.13.2. Format

 <FREE_RESPONSE> ::= <Version>
                     <Message Type>
                     <Overall Length>
                     <Client ID>
                     <Bind ID>
                     [Message Counter]

9.13.3. Behavior

 An RSIP host must always be ready to accept a FREE_RESPONSE, even if
 its lease on the specified bind ID is not yet expired.

Borella, et al. Experimental [Page 29] RFC 3103 RSIP Protocol Specification October 2001

9.14. QUERY_REQUEST

9.14.1. Description

 A QUERY_REQUEST message is used by an RSIP host to ask an RSIP
 gateway whether or not a particular address or network is local or
 remote.  The host uses this information to determine whether to
 contact the host(s) directly (in the local case), or via RSIP (in the
 remote case).
 This message defines an indicator parameter with a 1-byte value field
 and 2 defined values:
  1. 1 address
  2. 2 network

9.14.2. Format

 <QUERY_REQUEST> ::= <Version>
                     <Message Type>
                     <Overall Length>
                     <Client ID>
                     [Message Counter]
                     [Address Tuple]...
                     [Network Tuple]...
 where
 <Address Tuple> ::= <Indicator (address)>
                     <Address>
 <Network Tuple> ::= <Indicator (network)>
                     <Address (network)>
                     <Address (netmask)>

9.14.3. Behavior

 One or more address or network tuples may be specified.  Each tuple
 encodes a request regarding the locality (local or remote) of the
 encoded address or network.  If no tuple is specified, the RSIP
 gateway should interpret the message as a request for all tuples that
 it is willing to provide.  Note that the FQDN form of the address
 parameter cannot be used to specify the address of a network, and
 only the netmask form of the address parameter can be used to specify
 the netmask of a network.
 If an RSIP gateway cannot determine whether a queried host or network
 is local or remote, it SHOULD transmit a QUERY_RESPONSE with no
 response specified for the said host or network.

Borella, et al. Experimental [Page 30] RFC 3103 RSIP Protocol Specification October 2001

 The following message-specific error conditions exist:
  1. If the host is not registered with the gateway, the gateway

MUST respond with an ERROR_RESPONSE containing the

       REGISTER_FIRST error.
  1. If the message contains an incorrect client ID, the gateway

MUST respond with an ERROR_RESPONSE containing the

       BAD_CLIENT_ID error.

9.15. QUERY_RESPONSE

9.15.1. Description

 A QUERY_RESPONSE message is used by an RSIP gateway to answer a
 QUERY_REQUEST from an RSIP host.
 This message defines an indicator parameter with a 1-byte value field
 and 4 defined values:
  1. 1 local address
  2. 2 local network
  3. 3 remote address
  4. 4 remote network

9.15.2. Format

 <QUERY_RESPONSE> ::= <Version>
                      <Message Type>
                      <Overall Length>
                      <Client ID>
                      [Message Counter]
                      [Local Address Tuple]...
                      [Local Network Tuple]...
                      [Remote Address Tuple]...
                      [Remote Network Tuple]...
 where
 <Local Address Tuple> ::= <Indicator (local address)>
                           <Address>
 <Local Network Tuple> ::= <Indicator (local network)>
                           <Address (network)>
                           <Address (netmask)>
 <Remote Address Tuple> ::= <Indicator (remote address)>
                            <Address>

Borella, et al. Experimental [Page 31] RFC 3103 RSIP Protocol Specification October 2001

 <Remote Network Tuple> ::= <Indicator (remote network)>
                            <Address (network)>
                            <Address (netmask)>

9.15.3. Behavior

 An RSIP gateway has some leeway in how it responds to a
 QUERY_REQUEST.  It may just provide the information requested, if it
 can provide such information.  It may provide its complete list of
 address and networks, in order to minimize the number of requests
 that the host needs to perform in the future.  How an RSIP gateway
 responds may depend on network traffic considerations as well.
 If an RSIP gateway sends a QUERY_RESPONSE that does not contain any
 tuples, or a QUERY_RESPONSE that does not contain a tuple that
 applies to an associated tuple in the associated QUERY_REQUEST, this
 should be interpreted that the RSIP gateway does not know whether the
 queried host or network is local or remote.  Appropriate host
 behavior upon receipt of such a message is to assume that the queried
 host or network is remote.
 Note that an RSIP gateway is not expected to maintain a complete list
 of all remote hosts and networks.  In fact, a typical RSIP gateway
 will only maintain a list of the networks and hosts that it knows are
 local (private with respect to the RSIP host).

9.16. LISTEN_REQUEST

9.16.1. Description

 A LISTEN_REQUEST message is sent by an RSIP host that wants to
 register a service on a particular address and port number.  The host
 must include its client ID, local address parameter and ports
 parameters, and remote address and ports parameters.  The client MAY
 suggest a lease time and one or more tunnel types.

Borella, et al. Experimental [Page 32] RFC 3103 RSIP Protocol Specification October 2001

9.16.2. Format

 <LISTEN_REQUEST> ::= <Version>
                      <Message Type>
                      <Overall Length>
                      <Client ID>
                      <Address (local)>
                      <Ports (local)>
                      <Address (remote)>
                      <Ports (remote)>
                      [Message Counter]
                      [Lease Time]
                      [Tunnel Type]...

9.16.3. Behavior

 If the host wants to listen on a particular address or port, it may
 specify these in the address and ports parameters.  Otherwise it may
 leave one or both of these parameters with "don't care" values.
 If no remote flow policy is being used, the host MUST fill both the
 remote address and ports parameters with "don't care" values.  If
 macro-flow based remote policy is used, the host MUST specify the
 remote address, but MAY or MAY NOT specify the remote port(s).  If
 micro-flow based remote policy is used, the host MUST specify the
 remote address and ports parameter.
 Once a LISTEN_REQUEST has been granted, the RSIP gateway MUST forward
 all packets destined to the address and port in question to the host,
 even if the remote host address and port tuple has not been
 previously contacted by the host.
 LISTEN_REQUEST is not necessary for RSA-IP.
 The following message-specific error conditions exist:
  1. If the host is not registered with the gateway, the gateway

MUST respond with an ERROR_RESPONSE containing the

       REGISTER_FIRST error.
  1. If the message contains an incorrect client ID, the gateway

MUST respond with an ERROR_RESPONSE containing the

       BAD_CLIENT_ID error.
  1. If the local address parameter is a don't care value and the

RSIP gateway cannot allocate ANY addresses, the RSIP gateway

       MUST respond with an ERROR_RESPONSE containing the
       LOCAL_ADDR_UNAVAILABLE error.

Borella, et al. Experimental [Page 33] RFC 3103 RSIP Protocol Specification October 2001

  1. If the local address parameter is not a don't care value there

are five possible error conditions:

       o  If the RSIP gateway cannot allocate ANY addresses, it MUST
          respond with an ERROR_RESPONSE containing the
          LOCAL_ADDR_UNAVAILABLE error.
       o  If the RSIP gateway cannot allocate the requested address
          because it is in use, the RSIP gateway MUST respond with an
          ERROR_RESPONSE containing the LOCAL_ADDR_INUSE error.
       o  If the RSIP gateway cannot allocate the requested address
          because it is not allowed by policy, the RSIP gateway MUST
          respond with an ERROR_RESPONSE containing the
          LOCAL_ADDR_UNALLOWED error.
       o  If the RSIP gateway cannot allocate the requested address /
          port tuple because it is in use, the RSIP gateway MUST
          respond with an ERROR_RESPONSE containing the
          LOCAL_ADDRPORT_INUSE error.
       o  If the RSIP gateway cannot allocate the requested address /
          port tuple because it is not allowed by policy, the RSIP
          gateway MUST respond with an ERROR_RESPONSE containing the
          LOCAL_ADDRPORT_UNALLOWED error.
  1. If macro-flow based remote policy is used and the requested

remote address is not allowed by the RSIP gateway's policy, the

       RSIP gateway MUST respond with an ERROR_RESPONSE containing the
       REMOTE_ADDR_UNALLOWED error.
  1. If micro-flow based remote policy is used and the requested

remote address / port pair is not allowed by the RSIP gateway's

       policy, the RSIP gateway MUST respond with an ERROR_RESPONSE
       containing the REMOTE_ADDRPORT_UNALLOWED error.
  1. If an unsupported or unallowed tunnel type is specified, the

RSIP gateway MUST respond with an ERROR_RESPONSE containing the

       BAD_TUNNEL_TYPE error.
  1. If the host has not specified local or remote address or port

information in enough detail, the RSIP gateway MUST respond

       with an ERROR_RESPONSE containing the FLOW_POLICY_VIOLATION
       error.

Borella, et al. Experimental [Page 34] RFC 3103 RSIP Protocol Specification October 2001

9.17. LISTEN_RESPONSE

9.17.1. Description

 A LISTEN_RESPONSE message is used by an RSIP gateway to respond to a
 LISTEN_REQUEST message from an RSIP host.  The RSIP gateway MUST
 issue a bind ID, and specify the address and port which have been
 granted to the host.  The gateway must also specify a tunnel type and
 lease time.
 If no remote flow policy is being used, the gateway MUST fill both
 the remote address and ports parameters with "don't care" values.  If
 macro-flow based remote policy is used, the gateway MUST specify the
 remote address, but MAY or MAY NOT specify the remote port(s).  If
 micro-flow based remote policy is used, the gateway MUST specify the
 remote address and ports parameter.

9.17.2. Format

 <LISTEN_RESPONSE> ::= <Version>
                       <Message Type>
                       <Overall Length>
                       <Client ID>
                       <Bind ID>
                       <Address (local)>
                       <Ports (local)>
                       <Address (remote)>
                       <Ports (remote)>
                       <Tunnel Type>
                       <Lease Time>
                       [Address (tunnel endpoint)]
                       [Message Counter]

9.17.3. Behavior

 If no remote flow policy is being used, the gateway MUST fill both
 the remote address and ports parameters with "don't care" values.  If
 macro-flow based remote policy is used, the gateway MUST specify the
 remote address, but MAY or MAY NOT specify the remote port(s).  If
 micro-flow based remote policy is used, the gateway MUST specify the
 remote address and ports parameter.
 The address of a tunnel endpoint that is not the RSIP gateway MAY be
 specified.  If this parameter is not specified, the RSIP gateway MUST
 be assumed to be the tunnel endpoint.

Borella, et al. Experimental [Page 35] RFC 3103 RSIP Protocol Specification October 2001

10. Discussion

10.1. Use of Message Counters, Timeouts, and Retransmissions

 Message counters are conceptually similar to sequence numbers.  They
 are necessary to facilitate reliability when UDP is the transport
 protocol.  Each UDP message is marked with a message counter.  When
 such a message is transmitted, the message is stored in a "last
 message" buffer.  For RSIP hosts, a timer is set to expire at the
 appropriate timeout value.
 General rules:
  1. When an RSIP host transmits a message with a message counter

value of n, the RSIP gateway's response will contain a message

       counter value of n.
  1. An RSIP host will not increment its message counter value to

n+1 until it receives a message from the RSIP gateway with a

       message counter value of n.
  1. An RSIP gateway begins all sessions with a message counter

value of 1.

  1. If the message counter value reaches the maximum possible 32-

bit value, it will wrap around to 1, not 0.

  1. If a message with a message counter value of n is transmitted

by an RSIP host, but a timer expires before a response to that

       message is received, the copy of the message (from the "last
       message" buffer) is retransmitted.
  1. When an RSIP gateway receives a duplicate copy of a message

with a message counter value of n, it transmits the contents of

       its "last message" buffer.
  1. When the RSIP gateway transmits an asynchronous RSIP message

(an RSIP message for which there was no request by the RSIP

       host), a message counter value of 0 MUST be used.  Note that
       only three RSIP messages can be transmitted asynchronously:
       ERROR_RESPONSE, DE-REGISTER_RESPONSE, and FREE_RESPONSE.  These
       messages may also be transmitted in response to an RSIP host
       request, so their message counter values MAY be non-zero.
  1. If a message counter is not present in a message from an RSIP

host, but is required, the RSIP gateway MUST respond with an

       ERROR_RESPONSE containing the MESSAGE_COUNTER_REQUIRED error.

Borella, et al. Experimental [Page 36] RFC 3103 RSIP Protocol Specification October 2001

10.2. RSIP Host and Gateway Failure Scenarios

 When either the RSIP host or gateway suffers from an unrecoverable
 failure, such as a crash, all RSIP-related state will be lost.  In
 this section, we describe the sequence of events that will occur in
 both host and gateway failures, and how the host and gateway re-
 synchronize.

10.2.1. Host Failure

 After a host failure, the host will reboot and be unaware of any RSIP
 state held on its behalf at the gateway.
 If the host does not immediately attempt to re-establish a session,
 it may receive RSIP packets on the RSIP client application port that
 it was using before it rebooted.  If an RSIP client application is
 not active on this port, these packets will be responded to with ICMP
 port unreachable messages.  If TCP is the transport protocol, it is
 likely that the connection will be terminated with a TCP RST.  If an
 RSIP client is active on this port, it will not recognize the session
 that these packets belong to, and it SHOULD silently ignore them.
 The RSIP host may also receive packets from a remote host with which
 it was communicating before it rebooted.  These packets will be
 destined to the RSIP tunnel interface, which should not exist.  Thus
 they SHOULD be silently discarded by the RSIP host's stack, or the
 RSIP host will transmit appropriate ICMP messages to the tunnel
 endpoint (e.g., the RSIP gateway).  The behavior of the system with
 respect to sessions that were active before the reboot should be
 similar to that of a publically addressable non-RSIP host that
 reboots.
 Upon rebooting, an RSIP host may attempt to establish a new RSIP
 session with the RSIP gateway.  Upon receiving the REGISTER_REQUEST
 message, the RSIP gateway will be able to determine that, as far as
 it is concerned, the RSIP host is already registered.  Thus, it will
 transmit an ERROR_RESPONSE with the ALREADY_REGISTERED message.  Upon
 receipt of this message, the RSIP host will know the client ID of its
 old registration, and SHOULD immediately transmit a DE-
 REGISTER_REQUEST using this client ID.  After this is accomplished,
 the states of the RSIP host and gateway have been synchronized, and a
 new RSIP session may be established.
 If the RSIP host does not de-register itself from the RSIP gateway,
 it will eventually receive a DE-REGISTER_RESPONSE from the gateway,
 when the gateway times out the host's session.  Since the DE-
 REGISTER_RESPONSE will refer to a client ID that has no meaning to

Borella, et al. Experimental [Page 37] RFC 3103 RSIP Protocol Specification October 2001

 the host, the host SHOULD silently ignore such a message.  At this
 point, the states of the RSIP host and gateway have been
 synchronized, and a new RSIP session may be established.

10.2.2. Gateway Failure

 After a gateway failure, the gateway will reboot and be unaware of
 any RSIP state held by an RSIP host.
 Since the gateway will not attempt to contact any of its RSIP hosts,
 a problem will first be detected when either an RSIP host sends an
 RSIP message to the gateway, an RSIP host sends tunneled data to the
 gateway, or data from a remote host intended for an RSIP host
 arrives.
 In the first case, the RSIP gateway SHOULD immediately response to
 all messages (except for a REGISTER_REQUEST) with an ERROR_RESPONSE
 with a REGISTER_FIRST error.  Upon receipt of such a message, an RSIP
 host MUST interpret the message as an indication of a loss of
 synchronization between itself and the RSIP gateway.  The RSIP host
 SHOULD immediately transmit a DE-REGISTRATION_REQUEST with its old
 client ID (which will generate another error, but this error SHOULD
 be ignored by the host).  At this point, the states of the RSIP host
 and gateway have been synchronized, and a new RSIP session may be
 established.
 In the second case, all data that an RSIP host sends to the tunneled
 interface of an RSIP server will either (1) be discarded silently,
 (2) responded to with an ICMP Destination Unreachable message, such
 as "Communication Administratively Prohibited", or (3) blindly routed
 to the intended destination.  In all of the above cases, the RSIP
 gateway will not have an explicit method to notify the RSIP host of
 the problem.  To prevent a long term communications outage, small
 lease times of several minutes can be set by the RSIP gateway.
 In the third case, the RSIP gateway SHOULD discard all incoming
 packets and/or respond with ICMP Port Unreachable messages.

10.3. General Gateway Policy

 There is a significant amount of RSIP gateway policy that may be
 implemented, but is beyond the scope of this document.  We expect
 that most of this policy will be site-specific or implementation-
 specific and therefore do not make any recommendations.  Examples of
 general gateway policy include:
  1. How ports are allocated to RSIP hosts.
  2. Preferred length of lease times.

Borella, et al. Experimental [Page 38] RFC 3103 RSIP Protocol Specification October 2001

  1. How flow policy is applied to which hosts.
  2. How an RSIP gateway with multiple public IP addresses that may

be leased by RSIP clients determines how to partition

       and/or lease these addresses.

10.4. Errors Not From the RSIP Protocol

 Once an RSIP host and gateway have established a relationship and the
 host is assigned resources to use, error may occur due to the host's
 misuse of the resources or its attempting to use unassigned
 resources.  The following error behavior is defined:
  1. If a host attempts to use a local address which it has not been

allocated, the RSIP gateway MUST drop the associated packet(s)

       and send the host an ERROR_RESPONSE containing the
       LOCAL_ADDR_UNALLOWED error.
  1. If a host attempts to use a local address / port tuple which it

has not been allocated, the RSIP gateway MUST drop the

       associated packet(s) and send the host an ERROR_RESPONSE
       containing the LOCAL_ADDRPORT_UNALLOWED error.
  1. If a host attempts to contact a remote address which has not

been properly specified or otherwise approved (e.g., via an

       ASSIGN_RESPONSE_RSAP-IP and macro or micro based remote flow
       policy), the RSIP gateway MUST drop the associated packet(s)
       and send the host an ERROR_RESPONSE containing the
       REMOTE_ADDR_UNALLOWED error.
  1. If a host attempts to contact a remote address / port tuple

which has not been properly specified or otherwise approved

       (e.g., via an ASSIGN_RESPONSE_RSAP-IP and micro based remote
       flow policy), the RSIP gateway MUST drop the associated
       packet(s) and send the host an ERROR_RESPONSE containing the
       REMOTE_ADDRPORT_UNALLOWED error.
  1. If a host attempts to establish or use an improper tunnel type,

the RSIP gateway MUST respond with an ERROR_RESPONSE containing

       the BAD_TUNNEL_TYPE error.
  1. If the RSIP gateway's detects a local fault which prevents its

RSIP server module from continuing operation, the RSIP gateway

       MUST respond with an ERROR_RESPONSE containing the
       INTERNAL_SERVER_ERROR error.

Borella, et al. Experimental [Page 39] RFC 3103 RSIP Protocol Specification October 2001

10.5. Address and Port Requests and Allocation

 Regardless of local flow policy, an RSIP host may "suggest" that it
 would like to use a particular local address and/or port number in a
 particular binding.  An RSIP gateway that cannot grant such a
 request, because the specified resources are already in use, MUST
 respond with an ERROR_RESPONSE containing the LOCAL_ADDR_INUSE or
 LOCAL_ADDRPORT_INUSE values.

10.6. Local Gateways and Flow Policy Interaction

 An RSIP host may initialize a publically accessible gateway (such as
 an FTP or HTTP gateway) by transmitting a LISTEN_REQUEST message to
 an RSIP gateway and receiving a LISTEN_RESPONSE.  However, unless no
 remote flow policy is used, the gateway will have to specify the
 address or address and port of a single remote host that will be
 allowed to contact it.  Obviously, such as restriction is not very
 useful for hosts that require their gateways to be accessible by any
 remote host.
 This indicates that there is a conflict between flow-based policy and
 support for gateways.  The main purpose of enforcing flow-based
 policy for LISTEN_REQUESTs is that it allows an RSIP gateway tight
 control over how an RSIP host uses ports and the associated
 accounting.  For example, an RSIP host, operating under remote
 micro-flow based policy and using a protocol such as FTP, will have
 to specify the address and port that it will receive FTP data on, as
 well as the address and port that the gateway will transmit data
 from, in a LISTEN_REQUEST.
 In general, an RSIP gateway may not allow arbitrary hosts to start
 public gateways because of the traffic and security concerns.  Thus,
 we recommend that if remote micro-flow based policy is used, that an
 RSIP gateway only allow public gateways on RSIP hosts via
 administrative override.
 Currently, RSIP hosts can only be identified by their local IP
 address or MAC address.

11. Security Considerations

 RSIP, in and of itself, does not provide security.  It may provide
 the illusion of security or privacy by hiding a private address
 space, but security can only be ensured by the proper use of security
 protocols and cryptographic techniques.

Borella, et al. Experimental [Page 40] RFC 3103 RSIP Protocol Specification October 2001

 An RSIP gateway should take all measures deemed necessary to prevent
 its hosts from performing intentional or unintentional denial-of-
 service attacks by request large sets of resources.
 Currently, RSIP hosts can only be identified by their local IP
 address or, in some cases, MAC address.  It is desirable to allow
 RSIP messages sent between a host and gateway to be authenticated.
 Further discussion of such authentication can be found in [RSIP-
 FRAME].
 Discussion of RSIP support for end-to-end IPsec can be found in
 [RSIP-IPSEC].

12. IANA Considerations

 All of the designations below have been registered by the IANA.
  1. RSIP port number: 4555
  2. RSIP error codes (see Appendix A).
  3. RSIP message type codes (see Appendix B).
  4. RSIP tunnel types, methods, and flow policies.
 RSIP parameter values are designated as follows:
  1. 0 Reserved
  2. 1-240 Assigned by IANA
  3. 241-255 Reserved for private use
 New registrations for the above namespaces are recommended to be
 allocated via the Specification Required method documented in
 [RFC2434].

13. Acknowledgements

 The authors would like to specifically thank Gabriel Montenegro, Pyda
 Srisuresh, Brian Carpenter, Eliot Lear, Dan Nessett, Gary Jaszewski,
 Naveen Rajanikantha, Sudhakar Ramakrishna, Jim March, and Rick Cobb
 for their input.  The IETF NAT working group as a whole has been
 extremely helpful in the ongoing development of RSIP.

Borella, et al. Experimental [Page 41] RFC 3103 RSIP Protocol Specification October 2001

14. Appendix A: RSIP Error Numbers

 This section provides descriptions for the error values in the RSIP
 error parameter.
 All errors are grouped into the following categories:
 100's: General errors.
    101: UNKNOWN_ERROR.  An error that cannot be identified has
       occurred.  This error should be used when all other error
       messages are inappropriate.
    102: USE_TCP.  A host has attempted to use UDP on a server that
       only supports TCP.
    103: FLOW_POLICY_VIOLATION: A host has not specified address or
       port information in enough detail for its assigned flow policy.
    104: INTERNAL_SERVER_ERROR: An RSIP server application has
       detected an unrecoverable error within itself or the RSIP
       gateway.
    105: MESSAGE_COUNTER_REQUIRED: An RSIP host did not use a message
       counter parameter in a situation in which it should have.
    106: UNSUPPORTED_RSIP_VERSION: An RSIP host sent a message with a
       version number that is not supported by the RSIP gateway.
 200's: Parameter and message errors.  The gateway uses these errors
    when it detects that a parameter or message is malformed, as well
    as when it does not understand a parameter or message.
    201: MISSING_PARAM.  The request does not contain a required
       parameter.
    202: DUPLICATE_PARAM.  The request contains an illegal duplicate
       parameter.
    203: EXTRA_PARAM.  The request contains a parameter that it should
       not.
    204: ILLEGAL_PARAM.  The gateway does not understand a parameter
       type.
    205: BAD_PARAM.  A parameter is malformed.

Borella, et al. Experimental [Page 42] RFC 3103 RSIP Protocol Specification October 2001

    206: ILLEGAL_MESSAGE.  The gateway does not understand the message
       type.  The message type is neither mandatory nor optional.
    207: BAD_MESSAGE.  A message is malformed and gateway parsing
       failed.
    208: UNSUPPORTED_MESSAGE: The host has transmitted an optional
       message that the gateway does not support.
 300's: Permission, resource, and policy errors.  The gateway uses
    these errors when a host has attempted to do something that it is
    not permitted to do, or something that violated gateway policy.
    301: REGISTER_FIRST.  The RSIP host has attempted to request or
       use resources without registering.
    302: ALREADY_REGISTERED.  The host has attempted to register again
       without first de-registering.
    303: ALREADY_UNREGISTERED.  The host has attempted to de-register
       but it is already in the unregistered state.
    304: REGISTRATION_DENIED.  The gateway will not allow the host to
       register.
    305: BAD_CLIENT_ID.  The host has referred to itself with the
       wrong client ID.
    306: BAD_BIND_ID.  The request refers to a bind ID that is not
       valid for the host.
    307: BAD_TUNNEL_TYPE.  The request refers to a tunnel type that is
       not valid for the host.
    308: LOCAL_ADDR_UNAVAILABLE.  The gateway is currently not able to
       allocate ANY local address, but the host may try again later.
    309: LOCAL_ADDRPORT_UNAVAILABLE.  The gateway is currently not
       able to allocate ANY local IP address / port tuple of the
       requested magnitude (i.e., number of ports), but the host may
       try again later.
    310: LOCAL_ADDR_INUSE.  The gateway was not able to allocate the
       requested local address because it is currently used by another
       entity.

Borella, et al. Experimental [Page 43] RFC 3103 RSIP Protocol Specification October 2001

    311: LOCAL_ADDRPORT_INUSE.  The gateway was not able to allocate
       the requested local address / port tuple because it is
       currently used by another entity.
    312: LOCAL_ADDR_UNALLOWED.  The gateway will not let the host use
       the specified local IP address due to policy.
    313: LOCAL_ADDRPORT_UNALLOWED.  The gateway will not let the host
       use the specified local address / port pair due to policy.
    314: REMOTE_ADDR_UNALLOWED.  The gateway will not allow the host
       to establish a session to the specified remote address.
    315: REMOTE_ADDRPORT_UNALLOWED.  The gateway will not allow the
       host to establish a session to the specified remote address /
       port tuple.
 400's: IPsec errors.  All errors specific to RSIP / IPsec operation.
    See [RSIP-IPSEC].

15. Appendix B: Message Types

 This section defines the values assigned to RSIP message types.  We
 also indicate which RSIP entity, host or gateway, produces each
 messages, and whether it is mandatory or optional.  All *_REQUEST
 messages are only to be implemented on hosts, while all *_RESPONSE
 messages are only to be implemented on gateways.  RSIP
 implementations (both host and gateway) MUST support all mandatory
 messages in order to be considered "RSIP compliant".

Borella, et al. Experimental [Page 44] RFC 3103 RSIP Protocol Specification October 2001

 Value    Message                 Implementation     Status
 ------------------------------------------------------------
  1     ERROR_RESPONSE                gateway        mandatory
  2     REGISTER_REQUEST              host           mandatory
  3     REGISTER_RESPONSE             gateway        mandatory
  4     DE-REGISTER_REQUEST           host           mandatory
  5     DE-REGISTER_RESPONSE          gateway        mandatory
  6     ASSIGN_REQUEST_RSA-IP         host           optional
  7     ASSIGN_RESPONSE_RSA-IP        gateway        optional
  8     ASSIGN_REQUEST_RSAP-IP        host           mandatory
  9     ASSIGN_RESPONSE_RSAP-IP       gateway        mandatory
 10     EXTEND_REQUEST                host           mandatory
 11     EXTEND_RESPONSE               gateway        mandatory
 12     FREE_REQUEST                  host           mandatory
 13     FREE_RESPONSE                 gateway        mandatory
 14     QUERY_REQUEST                 host           optional
 15     QUERY_RESPONSE                gateway        mandatory
 16     LISTEN_REQUEST                host           optional
 17     LISTEN_RESPONSE               gateway        optional

16. Appendix C: Example RSIP host/gateway transactions

 In this appendix, we present an exemplary series of annotated
 transactions between an RSIP host and an RSIP gateway.  All host to
 gateway traffic is denote by `C --> S' and all gateway to host
 traffic is denoted by `S --> C'.  Parameter values are denoted inside
 of parentheses.  Versions, message types, and overall lengths are not
 included in order to save space.  "Don't care" values are indicated
 by 0's.
 A ports parameter is represented by the number of ports followed by
 the port numbers, separated by dashes.  For example, 2-1012-1013
 indicates two ports, namely 1012 and 1013, while 16-10000 indicates
 16 ports, namely 10000-10015, and 4-0 indicates four ports, but the
 sender doesn't care where they are.
 IPv4 addresses are assumed.

16.1. RSAP-IP with Local Macro-flow Based Policy and No Remote Flow

     Policy
 This example exhibits the loosest policy framework for RSAP-IP.
 C --> S: REGISTER_REQUEST ()
    The host attempts to register with the gateway.

Borella, et al. Experimental [Page 45] RFC 3103 RSIP Protocol Specification October 2001

 S --> C: REGISTER_RESPONSE (Client ID = 1, Local Flow Policy =
    Macro, Remote Flow policy = None, Lease Time = 600)
    The gateway responds, assigning a Client ID of 1, local macro-
    flow based policy and no remote flow policy.  No RSIP method is
    indicated, so RSAP-IP is assumed.  No tunnel type is indicated,
    so IP-IP is assumed.  A lease time of 600 seconds is assigned.
 C --> S: ASSIGN_REQUEST_RSAP-IP: (Client ID = 1, Address (local) =
    0, Ports (local) = 4-0, Address (remote) = 0, Ports (remote) =
    0, Lease Time = 3600)
    The host requests an address and four ports to use with it, but
    doesn't care which address or ports are assigned.  The host
    does not specify the remote address or ports either.  The host
    suggests a lease time of 3600 seconds.
 S --> C: ASSIGN_RESPONSE_RSAP-IP: (Client ID = 1, Bind ID = 1,
    Address (local) = 149.112.240.156, Ports (local) = 4-1234,
    Address (remote) = 0, Ports (remote) = 0, Lease Time = 1800,
    Tunnel Type = IP-IP)
    The gateway responds by indicating that a bind ID of 1 has been
    assigned to IP address 149.112.240.156 with ports 1234-1237.
    Any remote host may be communicated with, using any remote port
    number.  The lease time has been assigned to be 1800 seconds,
    and the tunnel type is confirmed to be IP-IP.
    The host is now able to communicate with any host on the public
    network using these resources.
 C --> S: QUERY_REQUEST: (Client ID = 1, Indicator = network,
    Address (network) = 10.20.60.0, Address (netmask)
    255.255.255.0)
    The host asks the gateway if the network 10.20.60.0/24 is
    local.
 S --> C: QUERY_RESPONSE: (Client ID = 1, Indicator = network,
    Address (network) = 10.20.60.0, Address (netmask) =
    255.255.255.0)
    The gateway responds indicating that the network in question is
    local.
 C --> S: ASSIGN_REQUEST_RSAP-IP: (Client ID = 1, Address (local) =
    149.112.240.156, Ports (local) = 8-1238, Address (remote) = 0,
    Ports (remote) = 0, Lease Time = 1800)

Borella, et al. Experimental [Page 46] RFC 3103 RSIP Protocol Specification October 2001

    The host requests eight more particular ports for use with
    RSAP-IP with the same address.  A lease of 1800 seconds is
    requested.  IP-IP tunneling is implied by default.
 S --> C: ASSIGN_RESPONSE_RSAP-IP: (Client ID = 1, Bind ID = 2,
    Address (local) = 149.112.240.156, Ports (local) = 8-1305,
    Address (remote) = 0, Ports (remote) = 0, Lease Time = 1800)
    The gateway grants the request with the same address, but with
    a different set of ports.  IP-IP tunneling is implied by
    default.
 C --> S: FREE_REQUEST (Client ID = 1, Bind ID = 1)
    The host frees bind ID 1; i.e., ports 1234-1237 from IP address
    149.112.240.156.  Note that the address itself is still
    assigned to the host because the host is still assigned ports
    1305-1314.
 S --> C: FREE_RESPONSE (Client ID = 1, Bind ID = 1)
    The gateway acknowledges that Bind ID 1 has been freed.
 C --> S: EXTEND_REQUEST (Client ID = 1, Bind ID = 2, Lease Time =
    1800)
    The host request that the lease on bind ID 1 be extended for
    1800 seconds.
 S --> C: EXTEND_RESPONSE (Client ID = 1, Bind ID = 2, Lease Time =
    1800)
    The gateway confirms the request.
 S --> C: FREE_RESPONSE (Client ID = 1, Bind ID = 2)
    The gateway forces the host to free the resources of bind ID 2.
 C --> S: DE-REGISTER_REQUEST (Client ID = 1)
    The host de-registers with the sever.
 S --> C: DE-REGISTER_RESPONSE (Client ID = 1)
    The gateway acknowledges that the host has de-registered.

Borella, et al. Experimental [Page 47] RFC 3103 RSIP Protocol Specification October 2001

16.2. RSAP-IP with Local Micro-flow Based Policy and Remote Micro-

     flow Based Policy
 This example exhibits the strictest policy framework for RSAP-IP.
 C --> S: REGISTER_REQUEST ()
    The host attempts to register with the gateway.
 S --> C: REGISTER_RESPONSE (Client ID = 5, Local Flow Policy =
    Micro, Remote Flow policy = Micro, RSIP Method = RSAP-IP, RSIP
    Method = RSA-IP, Tunnel Type = IP-IP, Tunnel Type = GRE, Lease
    Time = 600)
    The gateway responds, assigning a Client ID of 5, local micro-
    flow based policy and remote micro-flow based policy.  Both
    RSAP-IP and RSA-IP are supported.  Both IP-IP and GRE tunnel
    types are supported.  A lease time of 600 seconds is assigned.
 C --> S: ASSIGN_REQUEST_RSAP-IP: (Client ID = 5, Address (local) =
    0, Ports (local) = 0, Address (remote) = 38.196.73.6, Ports
    (remote) = 21, Lease Time = 600, Tunnel Type = IP-IP)
    The host requests a local address and a port assignment to use
    with it.  The host indicates that it wants to contact host
    38.196.73.6 at port 21 (FTP control).  The host requests a
    lease time of 600 seconds and a tunnel type of IP-IP.
 S --> C: ASSIGN_RESPONSE_RSAP-IP: (Client ID = 5, Bind ID = 1,
    Address (local) = 149.112.240.156, Ports (local) = 2049,
    Address (remote) = 38.196.73.6, Ports (remote) = 21, Lease Time
    = 600, Tunnel Type = IP-IP)
    The gateway responds by indicating that a bind ID of 1 has been
    assigned to IP address 149.112.240.156 with port 2049.  Only
    host 38.196.73.6 at port 21 may be contacted.  The lease time
    has been assigned to be 600 seconds, and the tunnel type is
    confirmed to be IP-IP.
 C --> S: LISTEN_REQUEST: (Client ID = 5, Address (local) =
    149.112.240.156, Ports (local) = 2050, Address (remote) =
    38.196.73.6, Ports (remote) = 20)
    The host requests a listen port 2050 at the same address that
    it has been assigned.  Only host 38.196.73.6 from ports 20 (FTP
    data) will be able to contact it.

Borella, et al. Experimental [Page 48] RFC 3103 RSIP Protocol Specification October 2001

 S --> C: LISTEN_RESPONSE: (Client ID = 5, Address (local) =
    149.112.240.156, Ports (local) = 2050, Address (remote) =
    38.196.73.6, Ports (remote) = 20, Lease Time = 600, Tunnel Type
    = IP-IP)
    The gateway confirms the request and assigns a lease time of
    600 seconds and a tunnel type of IP-IP.
 C --> S: DE-REGISTER_REQUEST (Client ID = 5)
    The host de-registers with the sever.
 S --> C: DE-REGISTER_RESPONSE (Client ID = 5)
    The gateway acknowledges that the host has de-registered.  All
    of the host's bindings have been implicitly revoked.

16.3. RSA-IP with Local Macro-flow Based Policy and Remote Macro-

     flow based Policy
 This example exhibits a medium level of control for RSA-IP.
 C --> S: REGISTER_REQUEST ()
    The host attempts to register with the gateway.
 S --> C: REGISTER_RESPONSE (Client ID = 3, Local Flow Policy =
    Macro, Remote Flow policy = Macro, RSIP Method = RSAP-IP, RSIP
    Method = RSA-IP, Tunnel Type = IP-IP, Tunnel Type = L2TP, Lease
    Time = 600)
    The gateway responds, assigning a Client ID of 3, local macro-
    flow based policy and remote macro-flow based policy.  Both
    RSAP-IP and RSA-IP are supported.  Both IP-IP and L2TP tunnel
    types are supported.  A lease time of 600 seconds is assigned.
 C --> S: ASSIGN_REQUEST_RSA-IP: (Client ID = 3, Address (local) =
    0, Address (remote) = www.foo.com, Ports (remote) = 0, Lease
    Time = 3600, Tunnel Type = IP-IP)
    The host requests a local address and indicates that it wants
    to contact host www.foo.com.
 S --> C: ERROR_RESPONSE: (Error = REMOTE_ADDR_UNALLOWED, Client ID
    = 3)
    The gateway indicates that the host is not permitted to
    establish communication with www.foo.com.

Borella, et al. Experimental [Page 49] RFC 3103 RSIP Protocol Specification October 2001

 C --> S: ASSIGN_REQUEST_RSA-IP: (Client ID = 3, Address (local) =
    0, Address (remote) = www.bar.com, Ports (remote) = 0, Lease
    Time = 3600, Tunnel Type = IP-IP)
    The host requests a local address and indicates that it wants
    to contact host www.bar.com.
 S --> C: ASSIGN_RESPONSE_RSA-IP: (Client ID = 3, Bind ID = 1,
    Address (local) = 149.112.240.17, Address (remote) =
    www.bar.com, Ports (remote) = 0, Lease Time = 3600, Tunnel Type
    = IP-IP)
    The gateway responds by granting local IP address
    149.112.240.17 to the host, and permitting it to communicate
    with www.bar.com, at any port.  Requested lease time and tunnel
    type are also granted.
 C --> S: DE-REGISTER_REQUEST (Client ID = 3)
    The host de-registers with the sever.
 S --> C: DE-REGISTER_RESPONSE (Client ID = 3)
    The gateway acknowledges that the host has de-registered.  All
    of the host's bindings have been implicitly revoked.

17. Appendix D: Example RSIP host state diagram

 This appendix provides an exemplary diagram of RSIP host state.  The
 host begins in the unregistered state.  We assume that for UDP, if a
 message is lost, the host will timeout and retransmit another copy of
 it.  We recommend a 7-fold binary exponential backoff timer for
 retransmissions, with the first timeout occurring after 12.5 ms.
 This diagram does not include transitions for the LISTEN_REQUEST
 message.

Borella, et al. Experimental [Page 50] RFC 3103 RSIP Protocol Specification October 2001

                      send
                REGISTER_REQUEST
   +------------+              +------------+
   |            |------------->|Registration|<-- timeout/send

+—>|Unregistered|←————| Pending |— REGISTER_REQUEST

+————+ 7th timeout/recv
ERROR_RESPONSE
7th timeout/recv
DE-REGISTER_RESPONSE
send
send DE- v QUERY_REQUEST
Registered ←————— ———>Registered
De-registration Registered Query
Pending —————→ ←——– Pending
ERROR_RESPONSE
timeout/send
DE-REGISTER_REQUEST 7th timeout/recv
ERROR_RESPONSE
+—————-+
Go to Registered
+—————-+
timeout/send
Yes FREE_REQUEST
+
+ + v
+ Are all + recv Free Assignment
+ resources +←———-Pending Pending
+ +
+ +
+
No send recv
v ERROR_REQUEST ERROR_
+—————+ RESPONSE
Go to Assigned
+—————+
recv
+—————+ERROR_RESPONSE

Borella, et al. Experimental [Page 51] RFC 3103 RSIP Protocol Specification October 2001

Assigned ————–>+————-+——–> Assigned

+>|De-registration| | Assigned | | Query |

|    Pending    |<--------------+-------------+<--------|  Pending  |
+---------------+      send            ^  |             +-----------+
      ^  |       DE-REGISTER_REQUEST   |  |         send         ^ |
      |  |                             |  |     QUERY_REQUEST    | |
      |  |                             |  |                      | |
  timeout/send        7th/timeout/recv |  |send                  | |
  DE-REGISTER_         ASSIGN_RESPONSE |  |ASSIGN_REQUEST timeout/send
    REQUEST           or ERROR_RESPONSE|  |              QUERY_REQUEST
                                       |  |
                                       |  v
                                   +----------+
                                   | Assigned |
                                   |Assignment|
                                   | Pending  |
                                   +----------+
                                       ^  |
                                       |  |
                                   timeout/send
                                  ASSIGN_REQUEST

18. References

 [RFC1918]    Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot,
              G.J. and E. Lear, "Address Allocation for Private
              Internets", BCP 5, RFC 1918, February 1996.
 [RFC2119]    Bradner, S., "Key words for use in RFCs to indicate
              requirement levels", BCP 14, RFC 2119, March 1997.
 [RFC2434]    Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.
 [RFC2663]    Srisuresh, P. and M. Holdrege, "IP Network Address
              Translator (NAT) Terminology and Considerations", RFC
              2663, August 1999.
 [RSIP-FRAME] Borella, M. Lo, J., Grabelsky, D. and G. Montenegro,
              "Realm Specific IP: Framework", RFC 3102, October 2001.
 [RSIP-IPSEC] Montenegro, G. and M. Borella, "RSIP Support for End-
              to-end IPSEC", RFC 3104, October 2001.

Borella, et al. Experimental [Page 52] RFC 3103 RSIP Protocol Specification October 2001

19. Authors' Addresses

 Michael Borella
 CommWorks
 3800 Golf Rd.
 Rolling Meadows IL 60008
 Phone: (847) 262-3083
 EMail: mike_borella@commworks.com
 David Grabelsky
 CommWorks
 3800 Golf Rd.
 Rolling Meadows IL 60008
 Phone: (847) 222-2483
 EMail: david_grabelsky@commworks.com
 Jeffrey Lo
 Candlestick Networks, Inc
 70 Las Colinas Lane,
 San Jose, CA 95119
 Phone: (408) 284 4132
 EMail: yidarlo@yahoo.com
 Kunihiro Taniguchi
 NEC USA
 C&C Research Labs.
 110 Rio Robles
 San Jose, CA 95134
 Phone: (408) 943-3031
 EMail: taniguti@ccrl.sj.nec.com

Borella, et al. Experimental [Page 53] RFC 3103 RSIP Protocol Specification October 2001

20. Full Copyright Statement

 Copyright (C) The Internet Society (2001).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Borella, et al. Experimental [Page 54]

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