VLSM Tree Routing Protocol
draft-shyam-vlsmtrp-00

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Last updated 2020-01-29
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INTERNET DRAFT                                          S. Bandyopadhyay
draft-shyam-vlsmtrp-00.txt                              January 26, 2020
Intended status: Experimental
Expires: July 26, 2020

                       VLSM Tree Routing Protocol
                       draft-shyam-vlsmtrp-00.txt

Abstract

   This is a light weight routing protocol applicable inside a network
   that appears in the form of a tree and distribution of address space
   takes place with the approach of VLSM. It is based on setting default
   route inside VLSM tree.  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
   includes IP-VPN with MPLS inside VLSM tree by extending RSVP-TE.

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   This Internet-Draft will expire on July 26, 2020.

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Bandyopadhyay             Expires July 26, 2020                 [Page 1]
Internet Draft         VLSM Tree Routing Protocol       January 26, 2020

1. Introduction

   This is a light weight routing protocol of provider network that
   appears in the form of a tree and distribution of address space takes
   place with the approach of VLSM. It is based on setting default route
   inside VLSM tree.  Inside a VLSM tree, all the physical ports of a
   switch are configured with their associated domain (i.e.
   NetAddress/NetMask). Routing table will contain static routes based
   on the entries configured on these ports. 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.  In
   order to support network management and explicit route option, root
   of the tree maintains an image of the entire tree. A section of the
   OSPF protocol without the SPF part is extended to get the image of
   the tree at the root.  This protocol is intended to be used in a real
   IP environment (e.g. NAT free environment with IPv6 or any new
   generation IP that may be emerged), but, it makes use of existing 32
   bits address space for illustration.  It expects addressing
   architecture of real IP space to have separate address space assigned
   for the routers; e.g. section 3.2.1 of architectural specification[1]
   states that address space with prefix "111" will be assigned for the
   routers. This document includes IP-VPN with MPLS inside VLSM tree by
   extending RSVP-TE.

2. Setting default route inside VLSM tree

   As it has been stated earlier, there is no need to pass down the
   routing information of the external world inside a VLSM tree that
   acts as a stub. 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.

   Following figure 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 network CN-A. Switch SW-G assigns address block 11.1.20.0/24
   and 11.1.21.0/24 to two customers CN-B and CN-C; where as switch SW-E
   assigns address block 11.1.30.0/24 to customer network CN-D.

   Routing inside the tree takes place with the following principle.

Bandyopadhyay             Expires July 26, 2020                 [Page 2]
Internet Draft         VLSM Tree Routing Protocol       January 26, 2020
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