Internet DRAFT - draft-ietf-ospf-multi-instance
draft-ietf-ospf-multi-instance
Network Working Group A. Lindem
Internet-Draft Ericsson
Updates: 2328 (if approved) A. Roy
Intended status: Standards Track S. Mirtorabi
Expires: July 22, 2012 Cisco Systems
January 19, 2012
OSPFv2 Multi-Instance Extensions
draft-ietf-ospf-multi-instance-09.txt
Abstract
OSPFv3 includes a mechanism to support multiple instances of the
protocol running on the same interface. OSPFv2 can utilize such a
mechanism in order to support multiple routing domains on the same
subnet.
This document defines the OSPFv2 instance ID to enable separate
OSPFv2 protocol instances on the same interface. Unlike OSPFv3 where
the instance ID can be used for multiple purposes, such as putting
the same interface in multiple areas, the OSPFv2 instance ID is
reserved for identifying protocol instances.
This document updates RFC 2328.
Status of this Memo
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This Internet-Draft will expire on July 22, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3
2. OSPFv2 Instance Packet Encoding . . . . . . . . . . . . . . . 4
3. OSPFv2 Interface Instance ID . . . . . . . . . . . . . . . . . 5
3.1. Sending and Receiving OSPFv2 packets . . . . . . . . . . . 5
3.2. Interface Instance ID Values . . . . . . . . . . . . . . . 5
4. State Sharing Optimizations between OSPFv2 instances . . . . . 6
5. OSPFv2 Authentication Impacts . . . . . . . . . . . . . . . . 7
6. Backward Compatibility and Deployment Considerations . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . . 11
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
OSPFv3 [OSPFV3] includes a mechanism to support multiple instances of
the protocol running on the same interface. OSPFv2 [OSPFV2] can
utilize such a mechanism in order to support multiple routing domains
on the same subnet.
This document defines the OSPFv2 instance ID to enable separate
OSPFv2 protocol instances on the same interface. Unlike OSPFv3 where
the instance ID can be used for multiple purposes, such as putting
the same interface in multiple areas, the OSPFv2 instance ID is
reserved for identifying protocol instances.
1.1. Requirements notation
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 [RFC-KEYWORDS].
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2. OSPFv2 Instance Packet Encoding
This document extends OSPFv2 with a mechanism to differentiate
packets for different instances sent and received on the same
interface. In support of this capability, a modified packet header
format with the Authentication Type field split into an Instance ID
and AuType.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version # | Type | Packet length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Area ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum | Instance ID | AuType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The OSPFv2 Packet Header
All fields are as defined in [OSPFV2] except that the Instance ID
field is new, and the AuType field is reduced to 8 bits from 16 bits
without any change in meaning. The Instance ID field is defined as
follows:
Instance ID
Enables multiple instances of OSPFv2 to be used on a single
interface. Each protocol instance would be assigned a separate
Instance ID; the Instance ID has local subnet significance only.
Received packets with an Instance ID not equal to one of the
Instance IDs corresponding to one of the configured OSPFv2
Instances for the receiving interface MUST be discarded.
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3. OSPFv2 Interface Instance ID
[OSPFV2] describes the conceptual interface data structure in section
9. The OSPFv2 Interface Instance ID is added to this structure. The
OSPFv2 Interface Instance ID has a default value of 0. Its setting
to a non-zero value may be accomplished through configuration.
3.1. Sending and Receiving OSPFv2 packets
When sending OSPFv2 packets, the OSPFv2 Interface Instance ID is set
in the OSPFv2 packet header. When receiving OSPFv2 packets, the
OSPFv2 Header Instance ID is used to aid in demultiplexing the packet
and routing it to the correct OSPFv2 instance. Received packets with
an Instance ID not equal to one of the configured OSPFv2 Instance IDs
on the receiving interface MUST be discarded.
3.2. Interface Instance ID Values
The following OSPFv2 Instance IDs have been defined:
0
Base IPv4 Instance - This is the default IPv4 routing instance
corresponding to default IPv4 unicast routing and the attendant
IPv4 routing table. Use of this instance ID provides backward
compatibility with the base OSPF specification [OSPFV2].
1
Base IPv4 Multicast Instance - This IPv4 instance corresponds to
the separate IPv4 routing table used for the Reverse Path
Forwarding (RPF) checking performed on IPv4 multicast traffic.
2
Base IPv4 In-band Management Instance - This IPv4 instance
corresponds to a separate IPv4 routing table used for network
management applications.
3-127
Private Use - These Instance IDs are reserved for definition and
semantics defined by the local network administrator. For
example, separate Interface Instance IDs and their corresponding
OSPFv2 instances could be used to support independent non-
congruent topologies for different classes of IPv4 unicast
traffic. The details of such deployments are beyond the scope of
this document.
The first three Interface Instance IDs are analogous to the topology
IDs defined in [RFC4915].
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4. State Sharing Optimizations between OSPFv2 instances
This is beyond the scope of this draft and is an area for further
study.
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5. OSPFv2 Authentication Impacts
Now that the AuType OSPFv2 header field has been reduced from 2
octets to 1 octet, OSPFv2 routers not supporting this specification
will fail packet authentication for any instance other than the
default (i.e., the Base IPv4 Unicast Instance). This is solely due
to the difference in field definition as opposed to any explicit
change to OSPFv2 authentication as described in Appendix D of RFC
2328 [OSPFV2] and RFC 5709 [RFC5709]. However, this is exactly what
is desired since OSPFv2 routers not supporting this specification
should only support the default instance (Refer to Section 6).
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6. Backward Compatibility and Deployment Considerations
When there are OSPFv2 routers that support OSPFv2 Multi-Instance
extensions on the same broadcast capable interface as OSPFv2 routers
that do not, packets with non-zero OSPFv2 header Instance IDs are
received by those legacy OSPFv2 routers. Since the non-zero Instance
ID is included in the AuType by these legacy OSPFv2 routers, it is
misinterpreted as a mismatched authentication type and the packet is
dropped. This is exactly what is expected and desired.
Previously, there was concern that certain implementations would log
every single authentication type mismatch. However, discussions with
implementers have led us to the conclusion that this is not as severe
a problem as we'd first thought and it will be even less of a problem
by the time the mechanism in this draft is standardized, implemented,
and deployed. Most implementations will dampen the logging of
errors. Hence, the more drastic mechanisms to avoid legacy OSPFv2
routers from receiving multicast OSPFv2 packets with non-zero
Instance IDs have been removed.
If the OSPF MIB as specified in [OSPF-MIB] is implemented, even the
damped generation of the ospfIfAuthFailure or ospfVirtIfAuthFailure
SNMP notifications would be undesirable in situations where legacy
OSPFv2 routers are deployed on the same subnet as OSPFv2 routers
supporting this specification. Consequently, it is recommended that
implementations that implement this specification and the OSPF MIB
also implement SNMP Notification filtering as specified in section 6
of [RFC3413].
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7. Security Considerations
The enhancement described herein doesn't add any additional security
considerations to OSPFv2. Security considerations for OSPFv2 are
described in [OSPFV2].
Given that only three OSPFv2 authentication types have been
standardized, it seems reasonable to reduce the OSPFv2 packet header
field to 8 bits.
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8. IANA Considerations
The size of the AuType field is reduced from 16 octets to 8 octets.
This changes the OSPF Authentication Codes registry in that the
values 256-65535 are no longer defined. There is no backward
compatibility issue since this range of values was previously defined
as "Reserved and should not be assigned".
A new registry is added for OSPFv2 Instance IDs. The allocation of
OSPFv2 Instance IDs is described below. Refer to Section 3.2 for
more information.
+-------------+----------------------+--------------------+
| Value/Range | Designation | Assignment Policy |
+-------------+----------------------+--------------------+
| 0 | Base IPv4 Unicast | Assigned |
| | Instance | |
| | | |
| 1 | Base IPv4 Multicast | Assigned |
| | Instance | |
| | | |
| 2 | Base IPv4 In-band | Assigned |
| | Management Instance | |
| | | |
| 3-127 | Private Use | Reserved for local |
| | | policy assignment |
| | | |
| 128-255 | Unassigned | Standards Action |
+-------------+----------------------+--------------------+
OSPFv2 Instance ID
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9. References
9.1. Normative References
[OSPFV2] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[OSPFV3] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008.
[RFC-KEYWORDS]
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
9.2. Informative References
[OSPF-MIB]
Joyal, D., Galecki, P., Giacalone, S., Baker, F., and R.
Coltun, "OSPF Version 2 Management Information Base",
RFC 4750, December 2006.
[RFC3413] Levi, D., Meyer, P., and B. Stewart, "Simple Network
Management Protocol (SNMP) Applications", STD 62,
RFC 3413, December 2002.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, June 2007.
[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
Authentication", RFC 5709, October 2009.
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Appendix A. Acknowledgments
The RFC text was produced using Marshall Rose's xml2rfc tool.
Thanks to Adrian Farrel for review and providing some suggested
improvements during the IESG review.
Thanks to Paul Wells for commenting on the backward compatibility
issues.
Thanks to Paul Wells and Vladica Stanisic for commenting during the
OSPF WG last call.
Thanks to Manav Bhatia for comments and being the document shepherd.
Thanks to Magnus Nystrom for comments under the auspices of the
Security Directorate review.
Thanks to Dan Romascanu for comments during the IESG review.
Thanks to Pete McCann for comments under the auspices of the Gen-ART
review.
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Authors' Addresses
Acee Lindem
Ericsson
102 Carric Bend Court
Cary, NC 27519
USA
Email: acee.lindem@ericsson.com
Abhay Roy
Cisco Systems
225 West Tasman Drive
San Jose, CA 95134
USA
Email: akr@cisco.com
Sina Mirtorabi
Cisco Systems
3 West Plumeria Drive
San Jose, CA 95134
USA
Email: sina@cisco.com
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