Network Working Group A. Zinin
Internet-Draft Alcatel
Intended status: Standards Track B. Friedman
Expires: July 13, 2007 A. Roy
L. Nguyen
D. Young
Cisco Systems
January 9, 2007
OSPF Link-local Signaling
draft-ietf-ospf-lls-02.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on July 13, 2007.
Copyright Notice
Copyright (C) The Internet Society (2007).
Zinin, et al. Expires July 13, 2007 [Page 1]
Internet-Draft OSPF Link-local Signaling January 2007
Abstract
OSPF is a link-state intra-domain routing protocol. OSPF routers
exchange information on a link using packets that follow a well-
defined fixed format. The format is not flexible enough to enable
new features which need to exchange arbitrary data. This memo
describes a backward-compatible technique to perform link-local
signaling, i.e., exchange arbitrary data on a link.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used In This Document . . . . . . . . . . . . 3
2. Proposed solution . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Options Field . . . . . . . . . . . . . . . . . . . . . . 5
2.2. LLS Data Block . . . . . . . . . . . . . . . . . . . . . . 5
2.3. LLS TLVs . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4. Extended Options TLV . . . . . . . . . . . . . . . . . . . 6
2.5. Cryptographic Authentication TLV (OSPFv2 ONLY) . . . . . . 7
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
4. Compatibility Issues . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. Normative References . . . . . . . . . . . . . . . . . . . 12
6.2. Informative References . . . . . . . . . . . . . . . . . . 12
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . . . . 15
Zinin, et al. Expires July 13, 2007 [Page 2]
Internet-Draft OSPF Link-local Signaling January 2007
1. Introduction
This document describes an extension to OSPFv2 [OSPFV2] and OSPFv3
[OSPFV3] allowing additional information to be exchanged between
routers on the same link. OSPFv2 and OSPFv3 packet formats are fixed
and do not allow for extension. This document proposes appending an
optional data block composed of Type/Length/Value (TLV) triplets to
existing OSPFv2 and OSPFv3 packets to carry this additional
information. Throughout this document, OSPF will be used when the
specification is applicable to both OSPFv2 and OSPFv3. Similarly,
OSPFv2 or OSPFv3 will be used when the text is protocol specific.
One potential way of solving this task could be introducing a new
packet type. However, that would mean introducing extra packets on
the network which may not be desirable and may cause backward
compatibility issues. This document describes how to exchange data
using standard OSPF packet types.
1.1. Conventions Used In This Document
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC2119 [KEY].
Zinin, et al. Expires July 13, 2007 [Page 3]
Internet-Draft OSPF Link-local Signaling January 2007
2. Proposed solution
To perform link-local signaling (LLS), OSPF routers add a special
data block at the end of OSPF packets or right after the
authentication data block when cryptographic authentication is used.
The length of the LLS block is not included into the length of OSPF
packet, but is included in the IPv4/IPv6 packet length. Figure 1
illustrates how the LLS data block is attached.
+---------------------+ -- -- +---------------------+
| IP Header | ^ ^ | IPv6 Header |
| Length = HL+X+Y+Z | | Header Length | | Length = HL+X+Y |
| | v v | |
+---------------------+ -- -- +---------------------+
| OSPF Header | ^ ^ | OSPFv3 Header |
| Length = X | | | | Length = X |
|.....................| | X | X |.....................|
| | | | | |
| OSPFv2 Data | | | | OSPFv3 Data |
| | v v | |
+---------------------+ -- -- +---------------------+
| | ^ ^ | |
| Authentication Data | | Y | Y | LLS Data |
| | v v | |
+---------------------+ -- -- +---------------------+
| | ^
| LLS Data | | Z
| | v
+---------------------+ --
Figure 1: LLS Data Block in OSPFv2 and OSPFv3
The LLS data block MAY be attached to OSPF hello and DD packets. The
data included in LLS block attached to a Hello packet MAY be used for
dynamic signaling, since Hello packets may be sent at any moment in
time. However, delivery of LLS data in Hello packets is not
guaranteed. The data sent with DBD packets is guaranteed to be
delivered as part of the adjacency forming process.
This memo does not specify how the data transmitted by the LLS
mechanism should be interpreted by OSPF routers. The interface
between OSPF LLS component and its clients is implementation
specific.
Zinin, et al. Expires July 13, 2007 [Page 4]
Internet-Draft OSPF Link-local Signaling January 2007
2.1. Options Field
A new bit, called L (L stands for LLS) is introduced to OSPF Options
field (see Figure 2a/2b). Routers set L bit in Hello and DBD packets
to indicate that the packet contains LLS data block. In other words,
LLS data block is only examined if L bit is set.
+---+---+---+---+---+---+---+---+
| * | O | DC| L |N/P| MC| E | * |
+---+---+---+---+---+---+---+-+-+
Figure 2a: OSPFv2 Options field
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+--+--+--+--+--+--+
| | | | | | | | | | | | | | |L|AF|*|*|DC| R| N|MC| E|V6|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+--+--+--+--+--+--+
Figure 2b: OSPFv3 Options field
The L-bit is only set in Hello and DBD packets.
2.2. LLS Data Block
The data block used for link-local signaling is formatted as
described below (see Figure 3 for illustration).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum | LLS Data Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| LLS TLVs |
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Format of LLS Data Block
The Checksum field contains the standard IP checksum of the entire
contents of the LLS block.
Zinin, et al. Expires July 13, 2007 [Page 5]
Internet-Draft OSPF Link-local Signaling January 2007
The 16-bit LLS Data Length field contains the length (in 32-bit
words) of the LLS block including the header and payload.
Implementations MUST NOT use the Length field in the IP packet header
to determine the length of the LLS data block.
Note that if the OSPF packet is cryptographically authenticated, the
LLS data block MUST also be cryptographically authenticated. In this
case the regular LLS checksum is not calculated and the LLS block
will contain a cryptographic authentication TLV (see Section 2.5).
The rest of the block contains a set of Type/Length/Value (TLV)
triplets as described in Section 2.3. All TLVs MUST be 32-bit
aligned (with padding if necessary).
2.3. LLS TLVs
The contents of LLS data block is constructed using TLVs. See Figure
4 for the TLV format.
The type field contains the TLV ID which is unique for each type of
TLVs. The Length field contains the length of the Value field (in
bytes) that is variable and contains arbitrary data.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Value .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Format of LLS TLVs
Note that TLVs are always padded to 32-bit boundary, but padding
bytes are not included in TLV Length field (though it is included in
the LLS Data Length field of the LLS block header).
2.4. Extended Options TLV
This subsection describes a TLV called Extended Options (EO) TLV.
The format of EO-TLV is shown in Figure 5.
Bits in the Value field do not have any semantics from the point of
view of LLS mechanism. This field MAY be used to announce some OSPF
capabilities that are link-specific. Also, other OSPF extensions MAY
Zinin, et al. Expires July 13, 2007 [Page 6]
Internet-Draft OSPF Link-local Signaling January 2007
allocate bits in the bit vector to perform boolean link-local
signaling.
The length of the Value field in EO-TLV is 4 bytes.
The value of the type field in EO-TLV is 1.
EO-TLV MUST only appear once in the LLS data block.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Options |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Format of EO TLV
Currently, [OOB] and [RESTART] use bits in the Extended Options field
of the EO-TLV.
The Extended Options bits are defined in Section 3.
2.5. Cryptographic Authentication TLV (OSPFv2 ONLY)
This document defines a special TLV that is used for cryptographic
authentication (CA-TLV) of the LLS data block. This TLV MUST be
included in the LLS block when the cryptographic (MD5) authentication
is enabled on the corresponding interface. The message digest of the
LLS block MUST be calculated using the same key and authentication
algorithm, as that used for the main OSPFv2 packet. The
cryptographic sequence number is included in the TLV and MUST be the
same as the one in the main OSPFv2 packet for the LLS block to be
considered authentic.
The TLV is constructed as shown Figure 6.
Zinin, et al. Expires July 13, 2007 [Page 7]
Internet-Draft OSPF Link-local Signaling January 2007
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2 | AuthLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. AuthData .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Format of Cryptographic Authentication TLV
The value of the Type field for CA-TLV is 2.
The Length field in the header contains the length of the data
portion of the TLV that includes 4 bytes for the Sequence Number and
the length of the message digest (MD5) block for the whole LLS block
in bytes (this will always be 16 bytes for MD5). So AuthLen field
will have value of 20.
The Sequence Number field contains the cryptographic sequence number
that is used to prevent simple replay attacks. For the LLS block to
be considered authentic, the Sequence Number in the CA-TLV MUST match
the Sequence Number in the OSPFv2 packet.
The AuthData contains the message digest calculated for the LLS data
block.
The CA-TLV MUST only appear once in the the LLS block. Also, when
present, this TLV SHOULD be the last TLV in the LLS block.
Zinin, et al. Expires July 13, 2007 [Page 8]
Internet-Draft OSPF Link-local Signaling January 2007
3. IANA Considerations
LLS TLV types are maintained by the IANA. Extensions to OSPF which
require a new LLS TLV type MUST be reviewed by an designated expert
from the routing area.
Following the policies outlined in [IANA], LLS type values in the
range of 0-32767 are allocated through an IETF Consensus action and
LLS type values in the range of 32768-65536 are reserved for private
and experimental use.
This document assigns the following LLS TLV types in OSPFv2/OSPFv3.
TLV Type Name Reference
0 Reserved
1 Extended Options [RFCNNNN]*
2 Cryptographic Authentication+ [RFCNNNN]*
3-32767 Reserved for assignment by the IANA
32768-65535 Private Use
*[RFCNNNN] refers to the RFC number-to-be for this document.
+ Cryptographic Authentication TLV is only defined for OSPFv2
This document also assigns the following bits for the Extended
Options bits field in the EO-TLV outlined in Section 2.5:
Extended Options Bit Name Reference
0x00000001 LSDB Resynchronization (LR) [OOB]
0x00000002 Restart Signal (RS-bit) [RESTART]
Other Extended Options bits will be allocated through an IETF
consensus action.
Zinin, et al. Expires July 13, 2007 [Page 9]
Internet-Draft OSPF Link-local Signaling January 2007
4. Compatibility Issues
The modifications to OSPF packet formats are compatible with standard
OSPF because LLS-incapable routers will not consider the extra data
after the packet; i.e., the LLS data block will be ignored by routers
which do not support the LLS extension.
Zinin, et al. Expires July 13, 2007 [Page 10]
Internet-Draft OSPF Link-local Signaling January 2007
5. Security Considerations
The described technique provides the same level of security as OSPF
protocol by allowing LLS data to be authenticated (see Section 2.5
for more details).
OSPFv3 has IPSec authentication built in. There are AH/ESP
techniques which operate on the whole OSPFv3 payload. So we do not
need a separate cryptographic TLV for OSPFv3.
Zinin, et al. Expires July 13, 2007 [Page 11]
Internet-Draft OSPF Link-local Signaling January 2007
6. References
6.1. Normative References
[IANA] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 2334,
October 1998.
[KEY] Bradner, S., "Key words for use in RFC's to Indicate
Requirement Levels", RFC 2119, March 1997.
[OSPFV2] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[OSPFV3] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6",
RFC 2740, December 1999.
6.2. Informative References
[OOB] Zinin, A., Roy, A., and L. Nguyen, "OSPF Out-of-band LSDB
resynchronization", draft-nguyen-ospf-oob-resync-06.txt
(work in progress), October 2006.
[RESTART] Zinin, A., Roy, A., and L. Nguyen, "OSPF Restart
Signaling", draft-nguyen-ospf-restart-06.txt (work in
progress), October 2006.
Zinin, et al. Expires July 13, 2007 [Page 12]
Internet-Draft OSPF Link-local Signaling January 2007
Appendix A. Acknowledgements
The authors would like to acknowledge Russ White and Acee Lindem for
their thoughtful review of this document.
Zinin, et al. Expires July 13, 2007 [Page 13]
Internet-Draft OSPF Link-local Signaling January 2007
Authors' Addresses
Alex Zinin
Alcatel
Sunnyvale
USA
Email: zinin@psg.com
Barry Friedman
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: friedman@cisco.com
Abhay Roy
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: akr@cisco.com
Liem Nguyen
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: lhnguyen@cisco.com
Derek Young
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: myeung@cisco.com
Zinin, et al. Expires July 13, 2007 [Page 14]
Internet-Draft OSPF Link-local Signaling January 2007
Full Copyright Statement
Copyright (C) The Internet Society (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Zinin, et al. Expires July 13, 2007 [Page 15]
