Internet DRAFT - draft-akinlar-zeroconf-multirouter

draft-akinlar-zeroconf-multirouter



NETWORK Working Group                                  Cuneyt Akinlar
INTERNET-DRAFT                                         David Braun
Category: Informational                                Sarit Mukherjee
<draft-akinlar-zeroconf-multirouter-01.txt>            Panasonic
Research August 15 2000

         Multi-Router Zeroconf Network Requirements

Status of this Memo

This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.

Internet-Drafts are working documents of the Internet Engineering Task
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The distribution of this memo is unlimited.  It is filed as <draft-
akinlar-zeroconf-multirouter-00.txt>, and expires February 15, 2001.
Please send comments to the authors.

Abstract

  Zero Configuration (Zeroconf) Networks are a particular class of
TCP/IP networks that may be established in the home, in small offices or
even for a variety of adhoc purposes. Zeroconf networks do not have and
should not be expected to have user configurable network infrastructure
such as DHCP, DNS and other administered network services. This is
because typical zeroconf network users neither have the skill nor the
desire to configure, administer or manage a network [1].

  The IETF Zeroconf Requirements draft [1] presents the zeroconf
protocol requirements for 4 areas: IP host configuration, domain name to
IP address resolution, IP multicast address allocation, and service
discovery. This draft builds on [1] and lists the zeroconf protocol
requirements for IP router configuration and dynamic routing protocol in
multi-router zeroconf networks.




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Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [6].

1. Introduction

  Zero Configuration (Zeroconf) Networks are a particular class of
TCP/IP networks that may be established in the home, in small offices or
on an adhoc basis . IETF Zeroconf Requirements draft [1] presents the
zeroconf protocol requirements for 4 areas: IP host configuration,
domain name to IP address resolution, IP multicast address allocation,
and service discovery. IP router configuration requirements are not
addressed in [1].

                  +---------------------------+
                  |   Non-Zeroconf Network    |
                  +------------+--------------+
                               |
                      +--------+-------+
   *******************|     Gateway    |************************
   * Zeroconf Network +-+--------------+                       *
   *                    |                                      *
   *                    |                                      *
   *           ***********              ***********            *
   *           *   R1    *              *   R2    *            *
   * +---+     *         *              *         *      +---+ *
   * | A |-----*1(X) 3(Z)*--------------*1(Z) 3(W)*------| E | *
   * +---+     *         *      |       *         *      +---+ *
   *           *   2(Y)  *    +---+     *   2(V)  *            *
   *           ***********    | C |     ***********            *
   *                |         +---+          |                 *
   *              +---+                    +---+               *
   *              | B |                    | D |               *
   *              +---+                    +---+               *
   *                                                           *
   *************************************************************

     Figure 1: A zeroconf network with 2 routers and a gateway

  Figure 1 shows a typical multi-router zeroconf network consisting of 2
internal zeroconf routers and 1 zeroconf gateway connecting the zeroconf
network to the Internet. The zeroconf network consists of 5 IP segments.
A zeroconf gateway is defined in [1] to be a specialized router. It
restricts packets that pass between the Zeroconf and non-zeroconf
networks to ensure autonomy of the zeroconf network and to avoid many
security problems. The gateways SHOULD act as boundary routers as



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defined in RFC 2365.

  In this document, we present the zeroconf protocol requirements for IP
router configuration and dynamic routing protocols in multi-router
zeroconf networks such as the one in Figure 1. The IP host configuration
protocol requirements as defined in [1] directly apply to this
environment. Therefore, we do not list them here.

Before we list the requirements, we define some terms used in this
draft:

A segment: A link-layer or several link-layer networks connected by
bridges. In a segment all hosts can communicate with each other using
only MAC addresses.

IP Subnet: Hosts who share the same subnet number of their IP addresses
constitute an IP subnet. The subnet number of an IP address is found by
ANDing the IP address with the netmask.


2. IP router Configuration Protocol Requirements

  Requirements for IP Router Configuration Protocol are the following:

  (1) Routers MUST configure an IP address for each of their interfaces.
  (2) Routers MUST configure a netmask for each of their interfaces.
  (3) The network number (subnet number) of all IP subnets within
      the zeroconf network MUST be unique.
  (4) The host number of an interface IP address MUST be unique within
      a single IP subnet.

  As Figure 1 shows, each segment in the zeroconf network MUST have a
unique subnet number. In the Figure, R1 has assigned unique subnet
numbers X, Y and Z to its interfaces 1, 2 and 3 respectively. Similarly,
R2 has assigned subnet numbers Z, V, and W to its interfaces 1, 2 and 3.
In an administered network the shared segments are usually assigned the
same subnet number at all the routers sharing the segment. In the
figure, both R1 and R2 have assigned subnet number Z to the shared
segment. Howeverm this is not a requirement. The network will work
correctly even if the routers assign different subnet numbers to the
shared segment provided that the routers know about all subnets in the
network through dynamic routing. So:

   (5) A shared segment between multiple routers SHOULD be
       assigned the same subnet number.

  Since subnet numbers must be unique within the zeroconf network:




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   (6) Routers MUST be able to detect subnet conflicts (use of the same
       subnet number for different physical segments) and resolve
       them.
   (7) Routers MUST be able to re-configure their IP address and
       netmask after new routers are connected to the network.

  When multiple routers are connected together, there might be subnet
number conflicts. Requirements (6) & (7) state that these conflicts MUST
be detected and resolved as new routers are added to the network.

3. Dynamic Routing Protocols

  In administered networks, routers use dynamic routing protocols such
as RIP [2-3] and OSPF [4] to communicate with each other to exchange
routing information. This allows routers in the network learn about all
subnets in the network so that hosts in any part of the network can
communicate with each other. The routers within the network will route
the packets from the source to the destination using the information
that they obtain from the dynamic routing protocol. In zeroconf networks
consisting of multiple routers, dynamic routing must also be performed.
The requirements for the zeroconf dynamic routing protocols are the
following:

  (1) Routers MUST learn about all the existing subnets in the
      zeroconf network.
  (2) Routers MUST learn about new subnets when they are connected to
      the zeroconf network.
  (3) Routers MUST learn that some routes do not exist in the zeroconf
      network anymore when those routes are removed from the zeroconf
      network.
  (4) Routers MAY use dynamic routing protocols to detect and resolve
      subnet conflicts.
  (5) If routers use a zeroconf dynamic routing protocol both to
      advertise routes and to detect and resolve subnet number
      conflicts, then the zeroconf dynamic routing protocol MUST NOT
      coexist with an administered routing protol on the zeroconf
      network.

4. References:

  [1] M. Hatting, Zeroconf Requirements,
      draft-ietf-zeroconf-reqts-03.txt, March 2000. A work in progress.

  [2] C. Hedrick, Routing Information Protocol, RFC 1058, June 1988.

  [3] G. Malkin, RIP Version 2, RFC 2453, November 1998.

  [4] J. Moy, OSPF Version 2, RFC 2328, April 1998.



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  [5] Bernard Aboba, Auto-Addressing in Multi-segment Networks,
      draft-aboba-zeroconf-multi-00.txt, Oct 1999. A work in progress.

  [6] Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.

4.  Authors' Addresses

Cuneyt Akinlar
Panasonic Research
2 Research Way
Princeton NJ 08540
Phone: +1 (609) 734-7356
EMail: akinlar@research.panasonic.com

David Braun
Panasonic Research
2 Research Way
Princeton NJ 08540
Phone: +1 (609) 734-7322
EMail: braun@research.panasonic.com

Sarit Mukherjee
Panasonic Research
2 Research Way
Princeton NJ 08540
Phone: +1 (609) 734-7347
EMail: sarit@research.panasonic.com























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