draft-ietf-ospf-2547-dnbit-01.txt   draft-ietf-ospf-2547-dnbit-02.txt 
Network Working Group Eric C. Rosen Network Working Group Eric C. Rosen
Internet Draft Peter Psenak Internet Draft Peter Psenak
Expiration Date: March 2004 Cisco Systems, Inc. Expiration Date: June 2004 Cisco Systems, Inc.
Padma Pillay-Esnault Padma Pillay-Esnault
Juniper Networks, Inc. Juniper Networks, Inc.
September 2003 December 2003
Using an LSA Options Bit to Prevent Looping in BGP/MPLS IP VPNs Using an LSA Options Bit to Prevent Looping in BGP/MPLS IP VPNs
draft-ietf-ospf-2547-dnbit-01.txt draft-ietf-ospf-2547-dnbit-02.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts. groups may also distribute working documents as Internet-Drafts.
skipping to change at page 2, line 9 skipping to change at page 2, line 9
routers and PE routers are routing peers, it is customary to run a routers and PE routers are routing peers, it is customary to run a
routing protocol between them. [VPN] allows a number of different routing protocol between them. [VPN] allows a number of different
PE-CE protocols. If OSPF is used as the PE-CE routing protocol, the PE-CE protocols. If OSPF is used as the PE-CE routing protocol, the
PE must execute additional procedures not specified in [VPN]; these PE must execute additional procedures not specified in [VPN]; these
procedures are specified in [OSPF-VPN]. These additional procedures procedures are specified in [OSPF-VPN]. These additional procedures
translate customer OSPF routes from a CE router into BGP routes. The translate customer OSPF routes from a CE router into BGP routes. The
BGP routes are sent to the other PE routers, which translate them BGP routes are sent to the other PE routers, which translate them
back into OSPF routes, and then distribute them to CE routers. back into OSPF routes, and then distribute them to CE routers.
During this translation, some of the information needed to prevent During this translation, some of the information needed to prevent
loops may be lost. The procedures specified in this document remedy loops may be lost. The procedures specified in this document remedy
this situation by specifying that one of the OSPF options bits be this situation by specifying that one of the options bits in the LSA
used to ensure that when a VPN route is sent from a PE to a CE, the (Link State Advertisements) header be used to ensure that when a VPN
route will be ignored by any PE which receives it back from a CE. route is sent from a PE to a CE, the route will be ignored by any PE
which receives it back from a CE.
Table of Contents Table of Contents
1 Specification of Requirements ........................ 2 1 Specification of Requirements ........................ 2
2 Introduction ......................................... 2 2 Introduction ......................................... 2
3 Information Loss and Loops ........................... 4 3 Information Loss and Loops ........................... 4
4 Using the LSA Options to Prevent Loops ............... 5 4 Using the LSA Options to Prevent Loops ............... 5
5 Acknowledgments ...................................... 5 5 Acknowledgments ...................................... 5
6 Authors' Addresses ................................... 5 6 Authors' Addresses ................................... 6
7 Normative References ................................. 6 7 Normative References ................................. 6
1. Specification of Requirements 1. Specification of Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119. document are to be interpreted as described in RFC 2119.
2. Introduction 2. Introduction
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Options Field with DN Bit Options Field with DN Bit
(RFC 2328, Section A.2) (RFC 2328, Section A.2)
When the PE receives, from a CE router, an LSA with the DN bit set, When the PE receives, from a CE router, an LSA with the DN bit set,
the information from that LSA MUST NOT be used during the OSPF route the information from that LSA MUST NOT be used during the OSPF route
calculation. As a result, the LSA is not translated into a BGP calculation. As a result, the LSA is not translated into a BGP
route. route.
This prevents routes learned via BGP from being redistributed to BGP. This prevents routes learned via BGP from being redistributed to BGP.
Note that the DN bit has no other effect on LSA handling. In
particular, an LSA with the DN bit set will be put in the topological
database, aged, flooded, etc., just as if DN was not set.
5. Acknowledgments 5. Acknowledgments
The idea of using the high-order options bit for this purpose is due The idea of using the high-order options bit for this purpose is due
to Derek Yeung. Thanks to Yakov Rekhter for his contribution to this to Derek Yeung. Thanks to Yakov Rekhter for his contribution to this
work. We also wish to thank Acee Lindem for his helpful comments. work. We also wish to thank Acee Lindem for his helpful comments.
6. Authors' Addresses 6. Authors' Addresses
Eric C. Rosen Eric C. Rosen
Cisco Systems, Inc. Cisco Systems, Inc.
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