Network Working Group A. Lindem
Internet-Draft Ericsson
Updates: 2328 (if approved) A. Roy
Intended status: Standards Track S. Mirtorabi
Expires: June 28, 2012 Cisco Systems
December 26, 2011
OSPF Multi-Instance Extensions
draft-ietf-ospf-multi-instance-07.txt
Abstract
OSPFv3 includes a mechanism for supporting multiple instances on the
same interface. OSPFv2 could benefit from such a mechanism in order
to support multiple routing domains on the same subnet. The OSPFv2
instance ID is reserved for support of separate OSPFv2 protocol
instances. This is different from OSPFv3 where it could be used for
other purposes such as putting the same interface in multiple areas.
OSPFv2 supports this capability using a separate subnet or the OSPF
multi-area adjacency capability.
Status of this Memo
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This Internet-Draft will expire on June 28, 2012.
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3
2. OSPFv2 Instance Packet Encoding . . . . . . . . . . . . . . . 4
3. OSPF Interface Instance ID . . . . . . . . . . . . . . . . . . 6
3.1. Sending and Receiving OSPF packets . . . . . . . . . . . . 6
4. State Sharing Optimizations between OSPF instances . . . . . . 7
5. OSPFv2 Authentication Impacts . . . . . . . . . . . . . . . . 8
6. Backward Compatibility and Deployment Considerations . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9.1. Normative References . . . . . . . . . . . . . . . . . . . 12
9.2. Informative References . . . . . . . . . . . . . . . . . . 12
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
OSPFv3 [OSPFV3] includes a mechanism for supporting multiple
instances on the same interface. OSPFv2 [OSPFV2] could benefit from
such a mechanism in order to support multiple routing domains on the
same subnet. The OSPFv2 Interface Instance ID is reserved for
support of separate OSPFv2 protocol instances. This is different
from OSPFv3 where it could be used for other purposes such as putting
the same interface in multiple areas. OSPFv2 supports this
capability using a separate subnet or the OSPF multi-area adjacency
capability [MULTI-AREA].
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
OSPFv2 currently doesn't offer a mechanism to differentiate packets
for different instances sent and received on the same interface. In
support of this capability, this document introduces 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
Version #
The OSPF version number - 2
Type
The OSPF packet type as specified [OSPFV2].
Packet length
The length of the OSPF protocol packet in bytes. This length
includes the standard OSPF header.
Router ID
The Router ID of the packet's source.
Area ID
A 32-bit number identifying the area corresponding the packet as
specified in [OSPFV2].
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Checksum
OSPF standard checksum calculation as specified in specified in
[OSPFV2].
Instance ID
Enables multiple instances of OSPF 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 OSPF Instances
for the receiving interface MUST be discarded.
AuType
OSPF authentication type as specified in specified in [OSPFV2].
Authentication
A 64-bit field for authentication data (dependent on the
Authentication Type as specified in the AuType field).
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3. OSPF Interface Instance ID
OSPF [OSPFV2] describes the conceptual interface data structure in
section 9. The OSPF Interface Instance ID will be added to this
structure. The OSPF Interface Instance ID will default to 0. Its
setting to a non-zero value may be accomplished through configuration
or implied by some usage beyond the scope of this document.
3.1. Sending and Receiving OSPF packets
When sending OSPF packets, if the OSPF Interface Instance ID has a
non-zero value, it will be set in the OSPF packet header. When
receiving OSPF packets, the OSPF Header Instance ID will be used to
aid in demultiplexing the packet and routing it to the correct OSPF
instance. Received packets with an Instance ID not equal to one of
the configured OSPF Instance IDs on the receiving interface MUST be
discarded.
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4. State Sharing Optimizations between OSPF 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, OSPF 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 OSPF 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 OSPF routers that support OSPF Multi-Instance
extensions on the same broadcast capable interface as OSPF routers
that do not, packets with non-zero OSPF header Instance IDs will be
received by those legacy OSPF routers. Since the non-zero Instance
ID will be included in the AuType by these legacy OSPF routers, it
will be misinterpreted as a mismatched authentication type and the
packet will be dropped. This is exactly what is expected and
desired.
Previously, there was concern that certain implementations would log
every single authentication type mismatch. Additionally, if
ospfIfAuthFailure SNMP generation is enabled as specified in
[OSPF-MIB], a separate trap would be generated for each received OSPF
packet with a non-zero Instance ID. 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 both the logging of
errors and the generation of identical SNMP traps. Hence, the more
drastic mechanisms to avoid legacy OSPF routers from receiving
multicast OSPF packets with non-zero Instance IDs have been removed.
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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 OSPF packet header
field to 8 bits.
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8. IANA Considerations
A new registry will be added for OSPF Instance IDs. The allocation
of OSPF Instance IDs is described below.
+-------------+----------------------+--------------------+
| 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 | Local Policy | 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
[MULTI-AREA]
Mirtorabi, S., Psenak, P., Lindem, A., and A. Oswal, "OSPF
Multi-Area Adjacency", RFC 5185, May 2008.
[OSPF-MIB]
Joyal, D., Galecki, P., Giacalone, S., Baker, F., and R.
Coltun, "OSPF Version 2 Management Information Base",
RFC 4750, December 2006.
[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 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 auspicies of the
Security Directorate 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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