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rfc:rfc2129

Network Working Group K. Nagami Request for Comments: 2129 Y. Katsube Category: Informational Y. Shobatake

                                                               A. Mogi
                                                          S. Matsuzawa
                                                             T. Jinmei
                                                              H. Esaki
                                                    Toshiba R&D Center
                                                            April 1997
Toshiba's Flow Attribute Notification Protocol (FANP) Specification

Status of this Memo

 This memo provides information for the Internet community.  This memo
 does not specify an Internet standard of any kind.  Distribution of
 this memo is unlimited.

Abstract

 This memo discusses Flow Attribute Notification Protocol (FANP),
 which is a protocol between neighbor nodes for the management of
 cut-through packet forwarding functionalities. In cut-through packet
 forwarding, a router doesn't have to perform conventional IP packet
 processing for received packets.  FANP indicates mapping information
 between a datalink connection and a packet flow to the neighbor node
 and helps a pair of nodes manage the mapping information.  By using
 FANP, routers (e.g., CSR; Cell Switch Router) can forward incoming
 packets based on their datalink-level connection identifiers,
 bypassing usual IP packet processing.  The design policy of the FANP
 is;
     (1)  soft-state cut-through path (Dedicated-VC) management
     (2)  protocol between neighbor nodes instead of end-to-end
     (3)  applicable to any connection oriented datalink platform

1. Background

 Due to the scalability requirement, connection oriented (CO) datalink
 platforms, e.g., ATM and Frame Relay, are going to be used as well as
 connection less (CL) datalink platforms, e.g., Ethernet and FDDI.
 One of the important features of the CO datalink is the presence of a
 datalink-level connection identifier.  In the CO datalink, we can
 establish multiple virtual connections (VCs) with their VC
 identifiers among the nodes. When we aggregate packets that have the
 same direction (e.g., having the same destination IP address) into a
 single VC, we can forward the packets in the VC without IP

Nagami, et. al. Informational [Page 1] RFC 2129 FANP Specification April 1997

 processing.  With this configuration, routers can decide which node
 is the next-hop for the packets based on the VC identifier.  CSRs [1]
 can forward the incoming packets using an ATM switch engine bypassing
 the conventional IP processing.  According to the ingress VPI/VCI
 value with ingress interface information, CSR determines the egress
 interface and egress VPI/VCI value.
 In order to configure the cut-through packet forwarding state, a pair
 of neighbor nodes have to share the mapping information between the
 packet flow and the datalink VC.  FANP (Flow Attribute Notification
 Protocol) described in this memo is the protocol to configure and
 manage the cut-through packet forwarding state.

2. Protocol Requirements and Future Enhancement

2.1 Protocol Requirements

 The followings are the protocol requirements for FANP.
 (1) Applicable to various types of CO datalink platforms
 (2) Available with various connection types (i.e., SVC, PVC, VP)
 (3) Robust operation
     The system should operate correctly even under the following
     conditions.
      (a) VC failure
          Some systems can detect VC failure as the function of
          datalink (e.g., OAM function in the ATM).  However, we can
          not assume all nodes in the system can detect VC failure.
          The system has to operate correctly, assuming that every
          node can not detect VC failure.
      (b) Message loss
          Control messages in the FANP may be lost.  The system has to
          operate correctly, even when some control messages are lost.
      (c Node failure
          A node may be down without any explicit notification to its
          neighbors.  The system has to operate correctly, even with
          node failure.
 Though FANP is not the protocol only for ATM, the following
 discussion assumes that the datalink is an ATM network.

Nagami, et. al. Informational [Page 2] RFC 2129 FANP Specification April 1997

2.2 Future Enhancement

 The followings are the future enhancements to be done.
      (1) Aggregated flow
        In this memo, we define the flow which contain source and
        destination IP address.  As this may require many VC
        resources, we also need a new definition of aggregated flow
        which includes several end-to-end flows.  The concrete
        definition of the aggregated flow is for future study.
      (2) Providing multicast service
      (3) Supporting IP level QOS signaling like RSVP
      (4) Supporting IPv6

3. Terminology and Definition

 o VCID (Virtual Connection IDentifier)
    Since VPI/VCI values at the origination and the termination points
    of a VC (and VP) may not be the same, we need an identifier to
    uniquely identify the datalink connection between neighbor nodes.
    We define this identifier as a VCID.  Currently, only one type of
    VCID is defined.  This VCID contains the ESI (End System
    Identifier) of a source node and the unique identifier within a
    source node.
 o Flow ID (Flow IDentifier)
    IP level packet flow is identified by some parameters in a packet.
    Currently, only one type of flow ID is defined.  This flow ID
    contains a source IP address and a destination IP address.  Note
    that flow ID used in this specification is not the same as the
    flow-id specified in IPv6.
 o Cut-through packet forwarding
    Packets are forwarded without any IP processing at the router
    using the datalink level information (e.g.,VPI/VCI).
    Internetworking level information (e.g., destination IP address)
    is mapped to the corresponding datalink-level identifier by using
    the FANP.
 o Hop-by-Hop packet forwarding
    Packets are forwarded using IP level information like conventional
    routers.  In ATM, cells are re-assembled into packets at the
    router to analyze the IP header.

Nagami, et. al. Informational [Page 3] RFC 2129 FANP Specification April 1997

 o Default-VC
    Default-VC is used for hop-by-hop packet forwarding.  Cells
    received from the Default-VC are reassembled into IP packets.
    Conventional IP processing is performed for these packets.  The
    encapsulation over the Default-VC is LLC for routed non-ISO
    protocols defined by RFC1483 [3].
 o Dedicated-VC
    Dedicated-VC is used for the specific IP packet flow identified by
    the flow-ID.  When the flow-ID for an incoming VC and an outgoing
    VC are the same at a CSR, it can forward the packets belonging to
    the flow through the cut-through packet forwarding.  The
    encapsulation over the Dedicated-VC is LLC for routed non-ISO
    protocols defined by RFC1483 [3].
 o Cut-through trigger
    When a FANP capable node receives a trigger packet, it tries to
    establish Dedicated-VC and to notify the mapping information
    between the Dedicated-VC and the IP packet flow which the received
    trigger packet belongs to.  Trigger packets are defined by the
    port-ID of TCP/UDP with the local policy of each FANP capable
    node.  In general, they would be the port-ID's of sessions with a
    long life-time and/or with large amount of packets; e.g., http,
    ftp and nntp.  Future implementation will include other triggers
    such as an arrival of resource reservation request.

4. Protocol Overview

 Figure 1 shows an operational overview of FANP.  In the figure, a
 cut-through packet forwarding path is established from host 1 (H1) to
 host 2 (H2) using two Dedicated-VCs.  H1 and H2 are connected to
 Ethernets, and R1, R2 and R3 are routers which can speak FANP.  R1
 and R3 have both an ATM interface and an Ethernet interface.  R2 has
 two ATM interfaces.
 When R1 receives an IP packet from H1, R1 analyzes the payload of the
 received IP packet whether it is a trigger packet or not.  When the
 received packet is a trigger packet, R1 fetches a Dedicated-VC to its
 downstream neighbor(R2) and sends FANP messages.  FANP is effective
 between the neighboring nodes only.  The same procedure would be
 performed between R2 and R3 independently from the procedure between
 R1 and R2.  The flow-ID of the packet flow from H1 to H2 is
 represented as id(H1,H2).  Here, id(H1,H2) is the set of the IP
 address of H1 and that of H2.

Nagami, et. al. Informational [Page 4] RFC 2129 FANP Specification April 1997

 The Dedicated-VC is released when no packet is transferred on it for
 a given period.  We do not need to explicitly indicate release of the
 Dedicated-VC to the neighbor node, since the state management in FANP
 is of soft-state, rather than of hard-state.
  +--+ Ethernet +--+   +-----+   +--+   +-----+   +--+ Ethernet +--+
  |H1|----------|R1|---| ATM |---|R2|---| ATM |---|R3|----------|H2|
  +--+          +--+   +-----+   +--+   +-----+   +--+          +--+
     trigger pkt
     |----------> trigger packet
                  |------------->   trigger packet
                     FANP          |-------------->  trigger pkt
                  <=============>        FANP        |----------->
                                   <==============>
                  |=============|
                   Dedicated-VC    |==============|
                                     Dedicated-VC
           Figure 1. Trigger packet and FANP initiation

5. Protocol Sequence

 FANP has the following five procedures, that are (1) Dedicated-VC
 selection, (2) VCID negotiation, (3) flow-ID notification, (4)
 Dedicated-VC refresh and (5) Dedicated-VC release.  Procedures (2),
 (3) and (4) have nothing to do with the kind of the Dedicated-
 VC;i.e.,SVC,PVC or VP.  On the contrary, the procedures (1) and (5)
 with SVC are different from the procedures with PVC and with VP.
 The detailed procedures are described in the following subsections.

5.1 Dedicated-VC Selection Procedure

 A VC is picked up in order to use as a Dedicated-VC.  The ways of
 picking up the Dedicated-VC is either of the followings.
 (1) A number of VCs are prepared in advance, and registered into an
    un-used VC list.  When a Dedicated-VC is needed, one of them is
    picked up from the un-used VC list.
 (2) A new VC is established through ATM signaling on demand.
 With ATM PVC/VP configuration, a Dedicated-VC is activated by the
 procedure (1).

Nagami, et. al. Informational [Page 5] RFC 2129 FANP Specification April 1997

 With ATM SVC configuration, a Dedicated-VC is activated by the
 procedure (1) or (2).  When the procedure (1) is used, some number of
 VCs are prepared in advance through ATM signaling.  These VCs are
 registered into the un-used VC list.  When a Dedicated-VC is needed,
 a VC is picked up from the un-used VC list.  When the procedure (2)
 is used, a Dedicated-VC is established through ATM signaling each
 time it is required.
 The procedure (1) can decrease a time to activate a Dedicated-VC.
 But the necessary VC resource will increase as it need to prepare
 additional VCs.  Which procedure should be applied to is a matter of
 local decision in each node, taking the economical requirement and
 the system responsiveness into account.
 A Dedicated-VC is used as a uni-directional VC, although it is
 generally bi-directional.  This means that packets are transferred
 only from upstream node to downstream node in the Dedicated-VC. The
 packets from downstream node to upstream node are transferred through
 the Default-VC or through another Dedicated-VC.

5.2 VCID Negotiation Procedure

 After the Dedicated-VC selection procedure, the upstream node
 transmits the PROPOSE message to the downstream node through the
 Dedicated-VC.  The PROPOSE message contains a VCID for the
 Dedicated-VC and IP address (target IP address) of downstream node.
 When the downstream node accepts the PROPOSE message, it transmits
 the PROPOSE ACK message to the upstream node through the Default-VC.
 With this procedure, the upstream and the downstream nodes (both
 end-points of the Dedicated-VC) can share the same indicator "VCID"
 for the Dedicated-VC.  When the downstream node can not accept the
 proposal from the upstream node with some reason (e.g., policy), the
 downstream node sends an ERROR message to the upstream node through
 the Default-VC.
 The procedure at the downstream node which has received PROPOSE
 message is;
  1. if(Target IP address of the PROPOSE message isn't equal to my IP
        address)
     then Goto end.
  2. if(The PROPOSE message should be refused)
     then  Send an ERROR(refuse by policy) message. Go to end.
  3. if(VCID Type in the PROPOSE message isn't known)
     then Send an ERROR(unknown VCID Type) message. Go to end.

Nagami, et. al. Informational [Page 6] RFC 2129 FANP Specification April 1997

  4. if(The VCID in the PROPOSE message is  the same as the VCID which
     has already been registered for another Dedicated-VC in the node)
     then Delete the registered VCID.
     Release the old Dedicated-VC.
  5. if(A VCID is registered for the Dedicated-VC which has received
     the PROPOSE message)
     then Delete the registered VCID.
  6. Register the mapping between VCID and  I/F, VPI, VCI for the
     Dedicated-VC.
  7. if(The mapping is successful)
     then Send a PROPOSE ACK.
     else Send an ERROR(resource unavailable).
 The upstream node retransmits the PROPOSE message when it neither
 receive PROPOSE ACK message nor ERROR message.  When the upstream
 node has received neither of the messages even with five
 retransmissions of the PROPOSE message, the Dedicated-VC picked up
 through the Dedicated-VC selection procedure should be released.
 Here, the number of retransmissions (five in this specification)is
 recommended value and can be modified in the future.
 The purpose of the VCID negotiation procedure is not only to share
 the VCID information regarding the Dedicated-VC, but also to confirm
 whether the Dedicated-VC is available and whether the neighbor node
 operates correctly.
 If the VCID negotiation procedure with a neighbor node always fails,
 it is considered that the node may not be FANP-capable node.
 Therefore the upstream node should not try the VCID negotiation
 procedure to that node for a certain time period.

5.3 Flow-ID Notification Procedure

 After the VCID negotiation procedure, the upstream node transmits an
 OFFER message to the downstream node through the Default-VC.  The
 OFFER message contains the VCID of the Dedicated-VC, the flow-ID of
 the packet flow transferred through the Dedicated-VC and the refresh
 interval of a READY message.
 When the downstream node receives the OFFER message from the upstream
 node, it transmits the READY message to the upstream node through the
 Default-VC in order to indicate that the OFFER message issued by the
 upstream node is accepted.  By the reception of the READY message,
 the upstream node realizes that the downstream node can receive IP
 packets transferred through the Dedicated-VC.

Nagami, et. al. Informational [Page 7] RFC 2129 FANP Specification April 1997

 The upstream node retransmits the OFFER message when it does not
 receive a READY message from the downstream node.  When the upstream
 node has not receive a READY message even with five retransmissions,
 the Dedicated-VC should be released.  Here, the number of
 retransmissions (i.e., five in this specification) is a recommended
 value and may be modified in the future.
 The node transmits an ERROR message to its neighbor in the following
 cases.  When the node receives the ERROR message, the Dedicated-VC
 should be released.
  (a) unknown VCID: The VCID in the message is unknown.
  (b) unknown VCID Type: The VCID Type is unknown.
  (c) unknown flow-ID Type: the flow-ID Type is unknown.
 When the downstream node accepts the OFFER message from the upstream
 node, it must send a READY message to the upstream node within the
 refresh interval offered by the upstream node.  If it can not, the
 downstream node sends the ERROR message (this refresh interval is not
 supported) to the upstream node.  The downstream node should accept
 the refresh interval larger than 120 seconds.  Therefore the
 downstream node shouldn't send the ERROR message (this refresh
 interval is not supported) when the refresh interval in the OFFER
 message is larger than 120 seconds.
 The following describes the procedure of the node which has received
 an OFFER message.
  1. if(unknown version in the OFFER message)
     then Discard the message.  Goto end.
  2. if(unknown VCID Type in the OFFER message)
     then Send an ERROR (unknown VCID Type) message.  Goto end.
  3. if(VCID in the OFFER message has not been registered)
     then Send an ERROR (unknown VCID) message.  Goto end.
  4. if(unknown Flow ID Type in the OFFER message)
     then Send an ERROR (unknown Flow ID Type) message.  Goto end.
  5. if(refuse Flow ID in the OFFER message)
     then Send an ERROR (refused by policy) message.  Goto end.
  6. if(refuse refresh interval in the OFFER message)
     then Send an ERROR(This refresh interval is not supported)
     message.  Goto end.

Nagami, et. al. Informational [Page 8] RFC 2129 FANP Specification April 1997

  7. if(the mapping between Flow ID and VCID already exists and
        Flow ID in the OFFER message is different from the registered
        Flow ID for the corresponding VCID)
     then Do Flow-ID removal procedure.  Goto end.
  8. Do the procedure of receiving the OFFER message.
  7. if(successful)
     then Send a READY message.
     else Send an ERROR (resource unavailable) message.
  8. end.
 The procedure of the node which has received a READY message is
 described.
  1. if(unknown version in the READY message)
     then Discard the message.  Goto end.
  2. if(unknown VCID Type in the READY message)
     then Send an ERROR (unknown VCID Type) message.  Goto end.
  3. if(VCID in the READY message has not been registered)
     then Send an ERROR (unknown VCID) message.  Goto end.
  4. if(unknown Flow ID Type in the READY message)
     then Send an ERROR (unknown Flow ID Type) message.  Goto end.
  5. if((the mapping between Flow ID and VCID doesn't exist)||
        (the mapping between Flow ID and VCID already exists and
         Flow ID in the READY message is different from registered Flow
         ID for the corresponding VCID))
     then Send an ERROR (unknown VCID) message.  Goto end.
  6. Do the procedure of receiving the READY message.
  7. end.

5.4 Flow ID Refresh Procedure

 While the downstream node receives IP packets through the Dedicated-
 VC, it should periodically (with a refresh interval) send the READY
 message to the upstream node.  When the downstream node does not
 receive any IP packet during the refresh interval, it does not send
 the READY message to the upstream node.

Nagami, et. al. Informational [Page 9] RFC 2129 FANP Specification April 1997

 While the upstream node continues to receive READY messages, it
 realizes that it can transmit the IP packets through the Dedicated-
 VC.  When it does not receive a READY message at all for a
 predetermined period (dead interval), it removes the mapping between
 the Flow IP and VCID.  The dead interval is defined below.
 When the upstream node falls into failure without the Flow ID removal
 procedure for a Dedicated-VC, its mapping must be removed by the
 downstream node.  The downstream node removes the mapping between the
 Flow ID and VCID for the Dedicated-VC when it does not receive any IP
 packet for a "removal period" (=refresh interval times m).
 The refresh interval, the dead interval and the removal period should
 satisfy the following equation.
  refresh interval < dead interval < removal period (=refresh
  interval times m)
  The recommended values are:
      refresh interval =  2 minutes
      dead interval    =  6 minutes (=refresh interval x 3)
      removal period  = 20 minutes (=refresh interval x 10)

5.5 Flow ID Removal Procedure

 When the upstream node realizes that the Dedicated-VC is not used, it
 performs a Flow ID removal procedure.
 The Flow ID removal procedure differs between the case of PVC/VP
 configuration and the case of SVC configuration.
 With the PVC/VP configuration, the upstream node issues a REMOVE
 message to the downstream node, and the downstream node sends back a
 REMOVE ACK message to the upstream node.  The upstream node
 retransmits REMOVE messages when it does not receive a REMOVE ACK
 message.  The upstream node assumes that the downstream node is in
 failure state when it dose not receive any REMOVE ACK message from
 the downstream node even with five REMOVE message retransmissions.

Nagami, et. al. Informational [Page 10] RFC 2129 FANP Specification April 1997

 With SVC configuration, two procedures are possible.  One is that the
 mapping between the Flow ID and the VCID is removed without the
 release of the ATM connection, which is the same procedure as the
 PVC/VP configuration.  The other procedure is that the mapping
 between the Flow ID and the VCID is removed by releasing the VC
 through ATM signaling.  The former procedure can promptly create and
 delete the mapping between Flow ID and VCID, since the ATM signaling
 does not have to be performed each time.  However, an un-used ATM
 connections have to be maintained by the node.  Which procedure is
 applied to is a matter of each CSR's local decision, taking the VC
 resource cost and responsiveness into account.
 The downstream node may want to remove the mapping between the Flow
 ID and the VCID.  When the upstream node receives the REMOVE message,
 it sends a REMOVE ACK message to the downstream node.
           +--+                              +--+
           |R1|------------------------------|R2|
           +--+                              +--+
             |           PROPOSE              |
             |===============================>|
    VCID     |       [VCID, target IP]        |
negotiation  |          PROPOSE ACK           |
             |<===============================|
             |            [VCID]              |
             |                                |
             |            OFFER               |
             |===============================>|
   Flow-ID   |       [VCID, flow-ID]          |
notification |            READY               |
             |<===============================|
             |       [VCID, flow-ID]          |
             |                                |
                  :         :           :
                  :         :           :
             |           READY                |
             |<===============================|
Dedicated-VC |       [VCID, flow-ID]          |
refresh      |           READY                |
             |<===============================|
             |       [VCID, flow-ID]          |
        Figure 2. Flow ID notification and refresh procedure

Nagami, et. al. Informational [Page 11] RFC 2129 FANP Specification April 1997

           +--+                              +--+
           |R1|------------------------------|R2|
           +--+                              +--+
             |                                 |
             |             REMOVE              |
             |================================>|
             |             [VCID]              |
             |                                 |
             |           REMOVE ACK            |
             |<================================|
             |             [VCID]              |
        (a) Flow ID removal (independent of ATM signaling)
           +--+                              +--+
           |R1|------------------------------|R2|
           +--+                              +--+
             |          ATM signaling          |
             |           (release)             |
             |<===============================>|
             |                                 |
          (b) Flow ID removal through ATM signaling
           Figure 3.  Flow ID removal procedure

6. Message Format

 FANP control procedure includes seven messages described from 6.2 to
 6.8.  Among them, a PROPOSE message used for VCID negotiation
 procedure uses an extended ATM ARP message format defined in RFC1577
 [2].  The other messages are encapsulated into IP packets.
 The destination IP address in the IP packet header signifies the
 neighbor node's IP address and the source IP address signifies
 sender's IP address.  Currently, the protocol ID for these messages
 is 110(decimal).  This protocol ID must be registered by IANA.
 The reserved field in the following packet format must be zero.

Nagami, et. al. Informational [Page 12] RFC 2129 FANP Specification April 1997

6.1 Field Format

6.1.1 VCID field

 VCID type value decides VCID field format.  Currently, only type "1"
 is defined.  The VCID field format of VCID type 1 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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    ESI of upstream node                       |
  +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                               |                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
  |                              ID                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ESI field: ESI of upstream node
     ID       : upstream node decides unique identifier.

6.1.2 Flow ID field

 Flow ID type value decides flow-ID field format.  Currently, flow-ID
 type "0" and "1" are defined.  The flow ID type value "0" signifies
 that the flow ID field is null.  When flow ID type value is "1", the
 format shown below is used.
   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   Source IP address                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                   Destination IP address                      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     Source IP address      : source IP address of flow
     Destination IP address : destination IP address of flow

6.2 PROPOSE message

 PROPOSE message uses the extended ATM-ARP message format [2] to which
 the VCID type and the VCID field are added.  Type & Length fields are
 set to zero, because the messages don't need sender/target ATM
 address.  This message is transferred from the upstream node to the
 downstream node through the Dedicated-VC.
 PROPOSE message is transferred from the upstream node to the
 downstream node through the Dedicated-VC.

Nagami, et. al. Informational [Page 13] RFC 2129 FANP Specification April 1997

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Hardware Type = 0x13          |  Protocol Type = 0x0800       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | Type&Length 1 | Type&Length 2 |      Opereation Code          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |    Length 1   | Type&Length 3 | Type&Length 4 |   Length 2    |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     Sender IP Address                         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     Target IP Address                         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |   VCID Type   |VCID Length    |       Reserved                |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        VCID                                   |
  /                                                               /
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  Type&Length 1 ; Type & Length of sender ATM number = 0
  Type&Length 2 ; Type & Length of sender ATM subnumber = 0
  Type&Length 3 ; Type & Length of sender ATM number = 0
  Type&Length 4 ; Type & Length of sender ATM subnumber =0
  Length 1      ; Source IP address length
  Length 2      ; Target IP address length
  Operation code
           0x10 = PROPOSE
  VCID Type:   Currently , VCID Type = 1 is defined.
  VCID Length: Length of VCID field
  VCID :       VCID described previous

6.3 PROPOSE ACK

 PROPOSE ACK messages is transferred through the Default-VC.
   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       |Op code = 1    |        Checksum               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | VCID type     |Flow-ID type=0 |         Reserved              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                           VCID                                |
  /                                                               /
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Nagami, et. al. Informational [Page 14] RFC 2129 FANP Specification April 1997

  Version
      This field indicates the version   number of FANP.    Currently,
      Version = 1
  Operation Code
      This field  indicates the operation code   of the message. There
      are five operation codes, below.
      operation code = 1 : PROPOSE ACK message
  Checksum
      This field is the 16 bits checksum for whole body of FANP message.
      The checksum algorithm is same as the IP header.
  VCID Type
      This field indicates the VCID type.  Currently, only "1" is
      defined.

6.4 OFFER message

 OFFER message is transferred from an upstream node to a downstream
 node.  The following is the message format.
   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 = 1   | Op Code = 2   |        Checksum               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | VCID type     |Flow-ID type   |     Refresh Interval          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                           VCID                                |
  /                                                               /
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                         Flow-ID                               |
  /                                                               /
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  Refresh Interval
      This field indicates the interval of refresh timer.  The refresh
      interval is represented by second in integer.  This field is
      used only in OFFER message.  Recommended value is 120 (second).

Nagami, et. al. Informational [Page 15] RFC 2129 FANP Specification April 1997

6.5 READY message

 READY message is transfered from a downstream node to an upstream
 node. This message is transferred when the downstream node receives
 OFFER message. And this message is transferred periodically in each
 refresh interval. The following is the message format.
   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 = 1   | Op Code = 3   |        Checksum               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | VCID type     |Flow-ID type   |     Reserved                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                           VCID                                |
  /                                                               /
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                         Flow-ID                               |
  /                                                               /
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6.6 ERROR message

 ERROR message is transfered from a downstream node to an upstream
 node or from an upstream node to a downstream node. This message is
 transferred when some of the fields in the receive message is unknown
 or refused.  When the receive message is the ERROR message, ERROR
 message isn't sent.  VCID type ,VCID, Flow ID Type and Flow ID field
 in the ERROR message are filled with the same field in the receive
 message.
 The following is the message format.
   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 = 1   | Op Code = 4   |        Checksum               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | VCID type     |Flow-ID type   |     Error code                |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                           VCID                                |
  /                                                               /
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                         Flow-ID                               |
  /                                                               /
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Nagami, et. al. Informational [Page 16] RFC 2129 FANP Specification April 1997

  Error Code = 1 : unknown VCID type
             = 2 : unknown Flow-ID type
             = 3 : unknown VCID
             = 4 : resource is unavailable
             = 5 : unavailable refresh interval is offered
             = 6 : refuse by policy

6.7 REMOVE message

 REMOVE message is transfered from a downstream node to an upstream
 node or vice versa.  This message is transferred to remove the
 mapping relationship between the flow ID and and the VCID. The node
 which receives REMOVE message must send REMOVE ACK message, even when
 VCID in the receive message isn't known .
 The following is the message format.
   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 = 1   | Op Code = 5   |        Checksum               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | VCID type     |Flow-ID type   |     Reserved                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                           VCID                                |
  /                                                               /
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6.8 REMOVE ACK message

 REMOVE ACK message is transferred from a downstream node to an
 upstream node or from an upstream node to a downstream node.  The
 following is the message format.
   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 = 1   | Op Code = 6   |        Checksum               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  | VCID type     |Flow-ID type   |     Reserved                  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                           VCID                                |
  /                                                               /
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Nagami, et. al. Informational [Page 17] RFC 2129 FANP Specification April 1997

7. Security Considerations

 Security issues are not discussed in this memo.

8. References

 [1] Katsube, Y., Nagami, K., and H. Esaki, "Router Architecture
     Extensions for ATM; overview", Work in Progress.
 [2] Laubach, M., "Classical IP and ARP over ATM", RFC 1577,
     October 1993.
 [3] Heinanen, J., "Multiprotocol Encapsulation over ATM Adaptation
     Layer 5", RFC 1483, July 1993.
 Ethernet is a registered trademark of Xerox Corp.  All other product
 names mentioned herein may be trademarks of their respective
 companies.

9. Authors' Addresses

 Ken-ichi Nagami
 R&D Center, Toshiba
 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki 210 Japan
 Phone : +81-44-549-2238
 EMail : nagami@isl.rdc.toshiba.co.jp
 Yasuhiro Katsube
 R&D Center, Toshiba
 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki 210 Japan
 Phone : +81-44-549-2238
 EMail : katsube@isl.rdc.toshiba.co.jp
 Yasuro Shobatake
 R&D Center, Toshiba
 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki 210 Japan
 Phone : +81-44-549-2238
 Email : masahata@csl.rdc.toshiba.co.jp
 Akiyoshi Mogi
 R&D Center, Toshiba
 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki 210 Japan
 Phone : +81-44-549-2238
 EMail : mogi@isl.rdc.toshiba.co.jp

Nagami, et. al. Informational [Page 18] RFC 2129 FANP Specification April 1997

 Shigeo Matsuzawa
 R&D Center, Toshiba
 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki 210 Japan
 Phone : +81-44-549-2238
 EMail : shigeom@isl.rdc.toshiba.co.jp
 Tatsuya Jinmei
 R&D Center, Toshiba
 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki 210 Japan
 Phone : +81-44-549-2238
 EMail : jinmei@isl.rdc.toshiba.co.jp
 Hiroshi Esaki
 R&D Center, Toshiba
 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki 210 Japan
 Phone : +81-44-549-2238
 EMail : hiroshi@isl.rdc.toshiba.co.jp

Nagami, et. al. Informational [Page 19]

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