Setting Default Route Inside VLSM Tree
draft-shyam-rt-inside-vlsm-tree-01

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INTERNET DRAFT                                          S. Bandyopadhyay
draft-shyam-rt-inside-vlsm-tree-01.txt                      July 1, 2018
Intended status: Proposed Standard
Expires: January 1, 2019

                 Setting Default Route Inside VLSM Tree
                 draft-shyam-rt-inside-vlsm-tree-01.txt

Abstract

   This document shows how to set default route inside VLSM tree.  With
   this approach routing information of the external world need not be
   passed down to the VLSM tree. It shows how RSVP-TE is extended to
   support IP-VPN with MPLS to support default route inside VLSM tree.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on January 1, 2019.

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Bandyopadhyay            Expires January 1, 2019                [Page 1]
Internet Draft             Real IP Framework                July 1, 2018

1. Introduction

   Inside a VLSM tree of provider assigned address space, traditionally
   BGP [1] is used to provide routing and to support VPN services [2].
   This document shows how routing is achieved inside a VLSM tree by
   setting default route instead of using BGP. With this approach
   routing information of the external world need not be passed down to
   the VLSM tree. Thus load inside a router gets reduced substantially.
   This document shows how RSVP-TE is extended to support IP-VPN with
   MPLS by setting default route inside a VLSM tree. Inside a customer
   network, if address space is distributed in the form of a VLSM tree,
   same approach can be applied in place of using a traditional routing
   algorithm.

2. Setting default route inside VLSM tree

   Inside a VLSM tree, a node of higher prefix can be divided into
   number of nodes with lower prefixes. Each divided node can further be
   subdivided with nodes of further lower prefixes. This process can be
   continued as long as it is desired or no more division is further
   possible.

                               +--------------+
                               |     SW-A     |
                               | 11.1.16.0/20 |
                               +-+-+------+-+-+
                                 | |      | |
                 +---------------+ |      | +----------------+
                 |                 |      |                  |
          +------+-----+ +---------+--+ +-+----------+ +-----+------+
          |    SW-B    | |    SW-C    | |    SW-D    | |   SW-E     |
          |11.1.16.0/21| |11.1.24.0/22| |11.1.28.0/23| |11.1.30.0/23|
          +---+----+---+ +------------+ +------------+ +--+---------+
              |    |                                      |
              |    +-------+                              |
              |            |                           +--+--+
      +-------+----+  +----+-------+                   |CN-D |
      |   SW-F     |  |    SW-G    |                   +-----+
      |11.1.16.0/22|  |11.1.20.0/22|                11.1.30.0/24
      +--+---------+  +--+------+--+
         |               |      |
         |               |      |
      +--+--+         +--+--+ +-+---+
      |CN-A |         |CN-B | |CN-C |
      +-----+         +-----+ +-----+
   11.1.16.0/24  11.1.20.0/24 11.1.21.0/24

Bandyopadhyay            Expires January 1, 2019                [Page 2]
Internet Draft             Real IP Framework                July 1, 2018

   Figure above shows a typical arrangement of VLSM tree of a service
   provider's network with IPv4 address space. Switch SW-A is connected
   to the outside world and maintains global routing table. It acts as
   the root of a VLSM tree that acts as a stub. It has been assigned an
   address block 11.1.16.0/20 which is distributed among its four
   children SW-B, SW-C, SW-D and SW-E with the approach of VLSM. Switch
   SW-B further divides its address space between switches SW-F and SW-
   G. Switch SW-F assigns an address block 11.1.16.0/24 to customer
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