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rfc:rfc1682

Network Working Group J. Bound Request for Comments: 1682 Digital Equipment Corporation Category: Informational August 1994

               IPng BSD Host Implementation Analysis

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 document was submitted to the IETF IPng area in response to RFC
 1550.  Publication of this document does not imply acceptance by the
 IPng area of any ideas expressed within.  Comments should be
 submitted to the big-internet@munnari.oz.au mailing list.

Overview

 This IPng white paper, IPng BSD Host Implementation Analysis,
 was submitted to the IPng Directorate to provide a BSD host point of
 reference to assist with the engineering considerations during the
 IETF process to select an IPng proposal.  The University of
 California Berkeley Software Distribution (BSD) TCP/IP (4.3 + 4.4)
 system implementation on a host is used as a point of reference for
 the paper.
 This document only reflects the author's personal analysis based on
 research and implementation experience for IPng, and does not
 represent any product or future product from any host vendor.  Nor
 should it be construed that it is promoting any specific IPng at this
 time.

Acknowledgments

 The author would like to acknowledge the many host implementation
 discussions and inherent knowledge gained from discussions with the
 following persons within Digital over the past year: Peter Grehan,
 Eric Rosen, Dave Oran, Jeff Mogul, Bill Duane, Tony Lauck, Bill Hawe,
 Jesse Walker, John Dustin, Alex Conta, and Fred Glover.  The author
 would also like to acknowledge like discussions from outside his
 company with Bob Hinden (SUN), Bob Gilligan (SUN), Dave Crocker
 (SGI), Dave Piscitello (Core Competence), Tracy Mallory (3Comm), Rob
 Ullmann (Lotus), Greg Minshall (Novell), J Allard (Microsoft), Ramesh
 Govinden (Bellcore), Sue Thompson (Bellcore), John Curran (NEARnet),

Bound [Page 1] RFC 1682 IPng BSD Host Implementation Analysis August 1994

 Christian Huitema (INRIA), and Werner Volgels (INESC).  The author
 would also like to thank Digital Equipment Corporation for the
 opportunity to work on IPng within the IETF as part of his job.

1. Introduction

 A host in the context of this white paper is a system that contains
 an operating system supporting a network subsystem as one of its
 parts, and an interprocess communications facility to access that
 network subsystem.  These hosts are often referenced as a
 Workstation, Server, PC, Super Computer, Mainframe, or an Embedded
 System (Realtime Devices).
 IPng will require changes to a hosts network software architecture.
 Those changes should be as transparent as possible to the existing
 IPv4 applications executing on hosts.
 After discussing the network software architecture for a BSD host the
 paper will discuss the perceived network software alterations,
 extended capabilities, transition software, and a deployment
 consideration for IPng hosts.
 The inclusive OR of all IPng proposals was used to develop the
 engineering considerations discussed in this paper.

2. Network Software Architecture

 The BSD host network software architecture consists essentially of
 three components: the interprocess communications facility, the
 network communications subsystem, and the network protocols
 supported. These three components are tightly coupled and must be
 integrated in a way that affords high performance for the
 applications that are dependent on these components to interoperate
 efficiently.  A BSD host implementation view of the TCP/IP protocol
 suite is depicted in the following network architecture diagram.

Bound [Page 2] RFC 1682 IPng BSD Host Implementation Analysis August 1994

 +-----------------------------------------------------------------+
 |                        Application Layer                        |
 |                                                                 |
 |                Socket and Network Library APIs                  |
 |                                                                 |
 |  BIND DNS                                                       |
 |  SNMP Management                                                |
 |                          User Space                             |
 +-----------------------------------------------------------------+
 |                         Kernel Space          AF_INET           |
 |                                        Communications Domain    |
 |  Socket Layer                                                   |
 |                                                                 |
 |                     Transport Layer TCP & UDP                   |
 |                                               Queues/Control    |
 |                                                 Blocks          |
 |                        Network Layer                            |
 |              +-----------------------------------+              |
 |              | IPv4 Modules  Discovery Multicast |              |
 |              |                ICMP       IGMP    |              |
 |              |                   Routing         |   Routing    |
 |              |                RIP        EGP     |   Tables     |
 |              |                OSPF       BGP     |              |
 |              |                I-IS-IS    IDRP    |              |
 |              +-----------------------------------+              |
 |                     Link Dependent Layer                        |
 |              +-----------------------------------+              |
 |              | ARP, RARP, InARP, NCPs, Addr Tbls |              |
 |              +-----------------------------------+              |
 |  Discovery & Interface                                          |
 |      Cache                                                      |
 |                     Data Link Layer                             |
 |              +-----------------------------------+              |
 |              | Ethernet, FDDI, ATM, HIPPI, PPP   |              |
 |              +-----------------------------------+              |
 +-----------------------------------------------------------------+

2.1 Interprocess Communications Facility

 The interprocess communications (IPC) facilities includes three
 critical parts:
    1.  The IPC mechanism to the network communications subsystem.
    2.  The ability to access a network protocol set within that
        subsystem.
    3.  The structures supporting the network communications
        subsystem.

Bound [Page 3] RFC 1682 IPng BSD Host Implementation Analysis August 1994

 The IPC facility has two implementation parts.  The part in user
 space and the part in kernel space within the operating system. This
 is often not differentiated and why in the previous network
 architecture diagram you will see sockets in both user and kernel
 space.  An IPC supports in user space an application program
 interface (API) which application developers use to access the
 network communications features of the host. These APIs have
 corresponding functions in the kernel space which execute the
 functions requested by the user space requests through the APIs.
 The sockets paradigm on a BSD host defines the data structure of the
 network address within a selected protocol family (communications
 domain) in the network subsystem.  This data structure consists of an
 address family, a port for the protocol selected, and a network
 address.
 The IPC facility on a host is dependent upon its interface to the
 BIND DNS application which is the defacto method when using TCP/IP to
 retrieve network addresses.
 Other interfaces that may be required by applications to properly set
 up the network connection within the IPC facility include:
 setting/getting options for the protocols used, obtaining/accessing
 information about networks, protocols, and network services, and
 sending/transmitting datagrams.

2.2 Network Communications Subsystem

 The network communications subsystem consists of the following
 generic parts as depicted in the previous network architecture
 diagram: transport layer, network layer, link dependent layer, and
 data link layer.  These may not be implemented as true distinct
 layers on a BSD host, but they are referenced in this white paper in
 that manner for purposes of discussion.
 The transport layer supports the application interface into the
 network communications subsystem and sets up the parametric pieces to
 initiate and accept connections.  The transport layer performs these
 functions through requests to the lower layers of the network
 communications subsystem.  The transport layer also supports the
 queues and protocol control blocks for specific network connections.
 The network layer supports the modules to build and extend the
 network layer datagram, the control protocol datagrams, and the
 routing abstraction on the host.  This layer of the network
 communications subsystem on a BSD host is often extended to provide
 both interior and exterior routing functionality.

Bound [Page 4] RFC 1682 IPng BSD Host Implementation Analysis August 1994

 The link dependent layer supports the modules that provide an
 interface for the network communications subsystem to map network
 addresses to physical addresses, and build the necessary cache so
 this information is available to the host network software.
 On a BSD host the network layer and link dependent layer together
 provide system discovery for hosts and routers.
 The data link layer supports the modules that define the structures
 for communicating with the hardware media used by the host on the
 local network.

2.3 Network Protocols

 The TCP/IP protocol suite as defined by the IETF RFC specifications
 are the set of network protocols used by this white paper for
 reference.

3. Network Software Alterations

 The IPng network software alterations to a BSD host perceived at this
 time are as follows:
    1.  Applications Embedding IPv4 Addresses.
    2.  Transport Interfaces and Network APIs.
    3.  Socket Layer and Structures.
    4.  Transport Layer.
    5.  Network Layer Components.
    6.  Link dependent Layer.

3.1 Applications Embedding IPv4 Addresses

 Internet style applications in this white paper are the set of
 protocols defined for an end user using TCP/IP to exchange messages,
 transfer files, and establish remote login sessions.
 Applications use the sockets network APIs to maintain an opaque view
 of the network addresses used to support connections across a
 network. Opaque in this context means that the application determines
 the network address for the connection and then binds that address to
 a socket.  The application then uses the reference defined for that
 socket to receive and transmit data across a network.
 An application that embeds an IPv4 network address within its
 datagram has made an underlying assumption that the format of that
 address is permanent.  This will cause a great problem when IPng
 causes addresses to change.  Thus far only one Internet style
 application has been determined to cause this problem and that is FTP

Bound [Page 5] RFC 1682 IPng BSD Host Implementation Analysis August 1994

 [1,2].

3.2 Transport Interfaces and Network APIs

 The transport interface and network API enhancements that must take
 place on a BSD host because of IPng are alterations that affect the
 size of the network address used by the socket data structure.
 Depending on how this is implemented on the host, supporting both
 IPv4 and IPng could require existing IPv4 applications to be
 recompiled.  In the worst case it could require modifications to the
 existing IPv4 applications software that accesses the network
 communications subsystem.
 There will have to be enhancements to the network APIs that an
 application uses to retrieve BIND DNS records to differentiate
 between IPv4 and IPng address requests.
 The network API enhancements and how they are implemented will affect
 the capability of any IPng proposal on a BSD host to be able to
 interoperate between an IPv4 only, an IPng only, and an IPng-IPv4
 host system.
 Depending on the IPng proposal selected the network options,
 services, and management objects will have to be extended at the
 transport interface so those features can be accessed by applications
 software.

3.3 Socket Layer and Structures

 The socket layer and structures will require changes to support any
 IPng proposals network address.  In addition new or removed options
 and services will need to be incorporated into the socket abstraction
 within the network communications subsystem.

3.4 Transport Layer

 The transport layer will need to be modified to support any new or
 removed services proposed by an IPng solution set.  The transport
 layer will become more overloaded to support the binding of either
 the IPv4 or IPng network layer components to differentiate the
 services and structures available to a host application.  The
 overload will also take place to support functionality removed in the
 network layer and moved to the transport layer if proposed by an IPng
 solution.
 It will also take some design thought to implement IPng so the
 hundreds of man years invested in performance improvements in the
 host transport layer are maintained.   This must be analyzed in depth

Bound [Page 6] RFC 1682 IPng BSD Host Implementation Analysis August 1994

 and should be part of the operational testing of any IPng proposal.

3.5 Network Layer Components

 The network layer components for IPng will require the greatest
 alterations on a host.  In addition a host will be required to
 maintain an integrated network layer below the transport layer
 software to support either the IPng or IPv4 network layer and
 associated components.
 Depending on the IPng selected the host alterations to the network
 layer components will range from complete replacement with new
 protocols to extensions to existing IPv4 network layer protocols to
 support IPng.
 All IPng proposals will affect the BSD host routing abstraction to
 maintain host software that supports interior and exterior routing.
 Depending on the proposal selected those changes can cause either a
 complete new paradigm or an update to the existing IPv4 paradigm.
 System discovery of nodes on the local subnetwork or across an
 internetwork path in all IPng proposals will require changes to the
 BSD host software network layer component.

3.6 Link dependent Layer

 The link dependent layer on a host will need to accommodate new IPng
 addresses and the system discovery models of any IPng proposal.

4. Extended Capabilities with IPng

 Extended capabilities that could be implemented by BSD hosts are
 listed below.  Many of these capabilities exist today with IPv4, but
 may require changes with the implementation of IPng.  Some of them
 will be new capabilities.

4.1 Autoconfiguration and Autoregistration

 Today hosts can provide autoconfiguration with DHCP using IPv4
 addresses. IPng hosts will be faced with having to provide support
 for existing IPv4 addresses and the new IPng addresses.  In addition
 the boot-strap protocol BOOTP used to boot minimal BSD host
 configurations (e.g., diskless nodes) will need to be supported by
 IPng hosts.

Bound [Page 7] RFC 1682 IPng BSD Host Implementation Analysis August 1994

4.2 PATH MTU Discovery

 PATH MTU discovery appears to be something each proposal is
 considering.  Alterations to the existing implementation of PATH MTU
 are perceived because changes are expected in system discovery.

4.3 Multicast

 Each proposal has depicted alterations to Multicast that will affect
 present BSD host implementations of IPv4 Multicast.  In addition it
 appears that the IPv4 unicast broadcast will be replaced by a
 multicast broadcast.

4.4 Flow Specification and Handling

 This will be an extended capability proposed by all IPngs'.

4.5 System Discovery

 Each proposal has depicted a new model for IPng system discovery of a
 host.

4.6 Translation and Encapsulation

 The routing abstraction in a BSD host will have to deal with the
 affect of any translation or encapsulation of network layer
 datagrams, if they are required by an IPng.

4.7 Network Layer Security

 It is perceived that network layer security will be required at the
 network layer component of IPng and this will have to be implemented
 by a BSD host.

4.8 Socket Address Structure

 The network kernel socket address structure will change because of
 IPng.

4.9 Network APIs

 The network APIs for a BSD host will have to be enhanced to support
 IPng.  In addition any new options available to the applications
 because of the IPng network service will have to be added as an
 option to the APIs.

Bound [Page 8] RFC 1682 IPng BSD Host Implementation Analysis August 1994

4.10 Network Management

 Network management for IPng will have to support new network objects
 as defined by the IPng proposal.  In addition the data structures in
 the BSD host network kernel used as information to display network
 topology will be altered by a new network layer datagram and
 associated components.

5. Transition Software

 Transition software in this white paper references the network
 software alterations on a host to support both IPv4 and IPng for
 applications and the hosts operating system network kernel.  It is
 the subject of another set of papers to identify the transition
 software required by network managers to transition their users from
 IPv4 to IPng.
 Transition software on a host will be required to maintain
 compatibility between IPv4 and IPng, and to manage both the existing
 IPv4 and IPng environments as follows:
    1.  BIND DNS record updates and handling by the application.
    2.  SNMP management interface and monitoring of host network
        structures.
    3.  APIs supporting IPv4 and IPng differentiation for the
        application.
    4.  Defacto network tools altered (e.g., tcpdump, traceroute,
        netstat).
    5.  ARP to new system discovery.
    6.  BOOTP diskless node support for IPng.
    7.  DHCP integration with IPng Autoconfiguration.
    8.  Routing table configuration on the BSD host (e.g., routed,
        ifconfig).
    9.  Selection of the network layer (IPv4 or IPng) at the
        transport layer.
    10.  New options and services provided by an IPng protocol.
    11.  IPv4 and IPng routing protocols in the network layer.
    12.  IPv4 and IPng system discovery in the network layer.
 These are only the highlights of the transition software that a host
 will have to deal with in its implementation of IPng.  The host
 network architecture diagram depicted previously will require
 software enhancements to each label in the diagram.
 It is very important that each IPng proposal provide a specification
 for a transition plan from IPv4 to IPng and their technical criteria
 for the interoperation between IPv4 and IPng.

Bound [Page 9] RFC 1682 IPng BSD Host Implementation Analysis August 1994

 It should also be a requirement that existing IPv4 applications not
 have to be recompiled when a host has implemented both an IPv4 and an
 IPng network layer and associated components.
 It is very desirable that when a host implements both an IPv4 and an
 IPng network layer and associated components that there is no
 performance degradation on the host compared to the performance of an
 existing IPv4 only host.
 It should not be a requirement by IPng that a host must support both
 an IPv4 and an IPng network layer.

6. A Deployment Consideration

 Complete and extensive technical specifications must be available for
 any IPng proposal, and a selection of any proposal must accommodate
 multiple implementations. The IPng Directorate should review proposed
 specifications for completeness.
 It is important that the IPng Directorate determine how long the CIDR
 IPv4 address plan can extend the life of IPv4 addresses on the
 Internet.  This variable can affect the time we have to deploy IPng
 and the proposed transition plans.

References

 [1] Gilligan, B., et. al., "IPAE: The SIPP Interoperability and
     Transition Mechanism", Work in Progress.
 [2] Piscitello, D., "FTP Operation Over Big Address Records
     (FOOBAR)", RFC 1639, Core Competence, Inc., June 1994.

Security Considerations

 Security issues are discussed in Section 4.7.

Author's Address

 Jim Bound
 Digital Equipment Corporation
 110 Spitbrook Road ZK3-3/U14
 Nashua, NH 03062-2698
 Phone: +1 603 881 0400
 EMail: bound@zk3.dec.com

Bound [Page 10]

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