draft-ietf-mpls-extended-admin-group-04.txt   draft-ietf-mpls-extended-admin-group-05.txt 
Network Working Group E. Osborne Network Working Group E. Osborne
Internet-Draft Internet-Draft
Intended status: Standards Track March 20, 2014 Intended status: Standards Track April 21, 2014
Expires: September 21, 2014 Expires: October 23, 2014
Extended Administrative Groups in MPLS-TE Extended Administrative Groups in MPLS-TE
draft-ietf-mpls-extended-admin-group-04 draft-ietf-mpls-extended-admin-group-05
Abstract Abstract
MPLS-TE advertises 32 administrative groups (commonly referred to as MPLS-TE advertises 32 administrative groups (commonly referred to as
"colors" or "link colors") using the Administrative Group sub-TLV of "colors" or "link colors") using the Administrative Group sub-TLV of
the Link TLV. This is defined for OSPFv2 (RFC3630), OSPFv3 (RFC5329) the Link TLV. This is defined for OSPFv2 (RFC3630), OSPFv3 (RFC5329)
and ISIS (RFC5305). and ISIS (RFC5305).
This document adds a sub-TLV to the IGP TE extensions, "Extended This document adds a sub-TLV to the IGP TE extensions, "Extended
Administrative Group". This sub-TLV provides for additional Administrative Group". This sub-TLV provides for additional
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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Extended Administrative Groups sub-TLV . . . . . . . . . . . 3 2. Extended Administrative Groups sub-TLV . . . . . . . . . . . 3
2.1. Packet Format . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Packet Format . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Admin group numbering . . . . . . . . . . . . . . . . . . 4 2.2. Admin group numbering . . . . . . . . . . . . . . . . . . 4
2.3. Backward compatability . . . . . . . . . . . . . . . . . 4 2.3. Backward compatability . . . . . . . . . . . . . . . . . 4
2.3.1. AG and EAG coexistence . . . . . . . . . . . . . . . 4 2.3.1. AG and EAG coexistence . . . . . . . . . . . . . . . 4
2.3.2. Desire for unadvertised EAG bits . . . . . . . . . . 5 2.3.2. Desire for unadvertised EAG bits . . . . . . . . . . 5
3. Signaling Extended Administrative Groups in RSVP . . . . . . 5 3. Security Considerations . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6 6.2. Informative References . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
Do we need more than 32 bits? Do we need more than 32 bits?
The IGP extensions to support MPLS-TE (RFCs 3630 [RFC3630] and 5305 The IGP extensions to support MPLS-TE (RFCs 3630 [RFC3630] and 5305
[RFC5305]) define a link TLV known as Administrative Group (AG) with [RFC5305]) define a link TLV known as Administrative Group (AG) with
a limit of 32 AGs per link. The concept of Administrative Groups a limit of 32 AGs per link. The concept of Administrative Groups
comes from section 6.2 of RFC 2702 [RFC2702], which calls them comes from section 6.2 of RFC 2702 [RFC2702], which calls them
Resource Classes. RFCs 3630 [RFC3630] and 5305 [RFC5305] describe Resource Classes. RFCs 3630 [RFC3630] and 5305 [RFC5305] describe
the mechanics of the TLV and use the term Administrative Groups the mechanics of the TLV and use the term Administrative Groups
(sometimes abbreviated herein as AGs), as does this document. (sometimes abbreviated herein as AGs), as does this document.
Networks have grown over time, and MPLS-TE has grown right along with Networks have grown over time, and MPLS-TE has grown right along with
them. Administative Groups as are advertised as a fixed-length them. Administrative Groups are advertised as a fixed-length 32-bit
32-bit bitmask. This can be quite constraining, as it is possible to bitmask. This can be quite constraining, as it is possible to run
run out of vaues rather quickly. One such use case is #5 in out of vaues rather quickly. One such use case is #5 in Section 6.2
Section 6.2 of RFC 2702 [RFC2702], using AGs to constrain traffic of RFC 2702 [RFC2702], using AGs to constrain traffic within specific
within specific topological regions of the network. A large network topological regions of the network. A large network may well have
may well have far more than 32 geographic regions. One particular far more than 32 geographic regions. One particular operator builds
operator builds their network along the lines of this use case, using their network along the lines of this use case, using AGs to flag
AGs to flag network regions down to the metro scale, e.g. Seattle, network regions down to the metro scale, e.g. Seattle, San Francisco,
San Francisco, Dallas, Chicago, St. Louis, etc. MPLS-TE tunnels are Dallas, Chicago, St. Louis, etc. MPLS-TE tunnels are then specified
then specified with affinities to include or exclude specific metro with affinities to include or exclude specific metro regions in their
regions in their path calculation. Each metro region is given its path calculation. Each metro region is given its own bit in the AG
own bit in the AG bitmask. This means that 32 bits can only bitmask. This means that 32 bits can only (cleanly) represent 32
(cleanly) represent 32 metro areas. It should be obvious that 32 may metro areas. It should be obvious that 32 may not be enough even for
not be enough even for a US-based network, nevermind a worldwide a US-based network, nevermind a worldwide network.
network.
There may be some opportunity for color reuse; that is, bit 0x8 may There may be some opportunity for color reuse; that is, bit 0x8 may
mean 'Seattle' or 'Prague' or 'Singapore' depending on the geography mean 'Seattle' or 'Prague' or 'Singapore' depending on the geography
in which it is used. In practice, coordinating this reuse is fraught in which it is used. In practice, coordinating this reuse is fraught
with peril and the reuse effectively becomes the limiting factor in with peril and the reuse effectively becomes the limiting factor in
MPLS-TE deployment. With this example it is not possible to build an MPLS-TE deployment. With this example it is not possible to build an
LSP which avoids Seattle while including Prague, as it is the same AG LSP which avoids Seattle while including Prague, as it is the same AG
value. value.
This document provides Extended Administrative Groups (EAGs). The This document provides Extended Administrative Groups (EAGs). The
number of EAGs has no fixed limit, it is constrained only by number of EAGs has no fixed limit, it is constrained only by
protocol-specific restrictions such as LSA or MTU size. While an protocol-specific restrictions such as LSA or MTU size. While an
operator may one day need to go beyond these protocol-specific operator may one day need to go beyond these protocol-specific
restrictions, allow for an arbitrary number of EAGs should easily restrictions, allow for an arbitrary number of EAGs should easily
provide the operator with hundreds or thousands of bit values, thus provide the operator with hundreds or thousands of bit values, thus
no longer making the number of AGs an impediment to network growth. no longer making the number of AGs an impediment to network growth.
EAG's intended use case is within a single domain. As such, this
document provides no support for signaling EAG. It provides no
analog to either the SESSION_ATTRIBUTE of C-Type 1 defined in
[RFC3209], nor the LSPA object of the Path Computation Element
Communication Protocol (PCEP) defined in [RFC5440].
2. Extended Administrative Groups sub-TLV 2. Extended Administrative Groups sub-TLV
The Extended Administrative Groups sub-TLV is used in addition to the This document defines a sub-TLV of the Link TLV for both OSPF
[RFC3630] and ISIS [RFC5305] called the Extended Administrative
Groups (EAG) sub-TLV. The EAG sub-TLV is used in addition to the
Administrative Groups when a node wishes to advertise more than 32 Administrative Groups when a node wishes to advertise more than 32
colors for a link. The EAG sub-TLV is optional. Coexistence of EAG colors for a link. The EAG sub-TLV is optional. Coexistence of EAG
and AG TLVs is covered in Section 2.3.1 of this document. and AG TLVs is covered in Section 2.3.1 of this document.
This document uses the term 'colors' as a shorthand to refer to This document uses the term 'colors' as a shorthand to refer to
particular bits with an AG or EAG. The examples in this document use particular bits with an AG or EAG. The examples in this document use
'red' to represent the least significant bit in the AG (red == 0x1), 'red' to represent the least significant bit in the AG (red == 0x1),
'blue' to represent the second bit (blue == 0x2). To say that a link 'blue' to represent the second bit (blue == 0x2). To say that a link
has a given color or that the specified color is set on the link is has a given color or that the specified color is set on the link is
to say that the corresponding bit or bits in the link's AG are set to to say that the corresponding bit or bits in the link's AG are set to
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Admin Group | | Extended Admin Group |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ........... | | ........... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Admin Group | | Extended Admin Group |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Type of the sub-TLV for OSPF and ISIS is TBD. The Length is the The Type of the sub-TLV for OSPF and ISIS is TBD. The Length is the
size of the Extended Admin Group (EAG) value in bytes. The EAG may size of the Extended Admin Group (EAG) value in bytes. The EAG may
be of any length, but MUST be a multiple of 4 bytes. The only limits be of any non-zero length, but MUST be a multiple of 4 bytes. The
on EAG size are those which are imposed by protocol-specific or only limits on EAG size are those which are imposed by protocol-
media-specific constraints (e.g. max packet length). specific or media-specific constraints (e.g. max packet length).
2.2. Admin group numbering 2.2. Admin group numbering
By convention, the existing Administrative Group TLVs are numbered 0 By convention, the existing Administrative Group TLVs are numbered 0
(LSB) to 31 (MSB). The EAG values are a superset of AG. That is, (LSB) to 31 (MSB). The EAG values are a superset of AG. That is,
bits 0-31 in the EAG have the same meaning and MUST have the same bits 0-31 in the EAG have the same meaning and MUST have the same
values as an AG flooded for the same link. If an EAG's length is values as an AG flooded for the same link. If an EAG's length is
more than 4 bytes, numbering for these additional bytes picks up more than 4 bytes, numbering for these additional bytes picks up
where the previous byte left off. For example, the least significant where the previous byte left off. For example, the least significant
bit in the 5th byte of an 8-byte EAG is referred to as bit 32. bit in the 5th byte of an 8-byte EAG is referred to as bit 32.
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There are two questions to consider for backward compatibility with There are two questions to consider for backward compatibility with
existing AG implementations - how do AG and EAG coexist, and what existing AG implementations - how do AG and EAG coexist, and what
happens if a node has matching criteria for unadvertised EAG bits? happens if a node has matching criteria for unadvertised EAG bits?
2.3.1. AG and EAG coexistence 2.3.1. AG and EAG coexistence
If a node advertises EAG it MAY also advertise AG. If a node advertises EAG it MAY also advertise AG.
If a node advertises both AG and EAG then the first 32 bits of the If a node advertises both AG and EAG then the first 32 bits of the
EAG MUST be identical to the advertised AG. If a receiving node EAG MUST be identical to the advertised AG.
notices that the AG differs from the first 32 bits of the EAG, it
SHOULD use the AG as the first 32 bits of the EAG, and SHOULD
indicate this mismatch to the operator.
If the AG and EAG advertised for a link differ, the EAG MUST take If both an AG and EAG are present, a receiving node MUST use the AG
priority. This allows nodes which do not support EAG to obtain some as the first 32 bits (0-31) of administrative color and use the EAG
for bits 32 and higher if present.
A receiving node that notices that the AG differs from the first 32
bits of the EAG, SHOULD report this mismatch to the operator.
This process allows nodes which do not support EAG to obtain some
link color information from the network, but also allow for an link color information from the network, but also allow for an
eventual migration away from AG. eventual migration away from AG.
2.3.2. Desire for unadvertised EAG bits 2.3.2. Desire for unadvertised EAG bits
The existing AG sub-TLV is optional; thus a node may be configured The existing AG sub-TLV is optional; thus a node may be configured
with a preference to include red or exclude blue, and be faced with a with a preference to include red or exclude blue, and be faced with a
link that is not advertising a value for either blue or red. What link that is not advertising a value for either blue or red. What
does an implementation do in this case? It shouldn't assume that red does an implementation do in this case? It shouldn't assume that red
is set, but it is also arguably incorrect to assume that red is NOT is set, but it is also arguably incorrect to assume that red is NOT
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Practically speaking this has not been an issue for deployments, as Practically speaking this has not been an issue for deployments, as
many implementations always advertise the AG bits, often with a many implementations always advertise the AG bits, often with a
default value of 0x00000000. However, this issue may be of more default value of 0x00000000. However, this issue may be of more
concern once EAGs are added to the network. EAGs may exist on some concern once EAGs are added to the network. EAGs may exist on some
nodes but not others, and the EAG length may be longer for some links nodes but not others, and the EAG length may be longer for some links
than for others. than for others.
Each implementation is free to choose its own method for handling Each implementation is free to choose its own method for handling
this question. However, to allow for maximum interoperability an this question. However, to allow for maximum interoperability an
implementation MUST treat desired but unadvertised EAG bits as if implementation SHOULD treat desired but unadvertised EAG bits as if
they are set to 0. Consider the case where a node wants to only use they are set to 0. Consider the case where a node wants to only use
links where the 127th bit of an EAG is set to 1. If a link is only links where the 127th bit of an EAG is set to 1. If a link is only
advertising 64 EAG bits, clearly the 127th EAG bit is not defined - advertising 64 EAG bits, clearly the 127th EAG bit is not defined -
that is, it is neither explicitly 0 nor 1. The node which wants the that is, it is neither explicitly 0 nor 1. The node which wants the
127th EAG bit to be 1 MUST NOT use this link, as the assumption is 127th EAG bit to be 1 MUST NOT use this link when implementing the
than an unadvertised bit is set to 0. recommended behavior, as the assumption is than an unadvertised bit
is set to 0.
A node MAY provide other strategies for handling this case. A A node MAY provide other strategies for handling this case. A
strategy which deviates from the recommended behavior in this strategy which deviates from the recommended behavior in this
document SHOULD be configurable, in order to provide maximum document SHOULD be configurable, in order to provide maximum
interoperability. interoperability.
3. Signaling Extended Administrative Groups in RSVP 3. Security Considerations
RSVP provides the ability to signal link affinity via the
SESSION_ATTRIBUTE object with C-Type 1 in RFC 3209 [RFC3209].
Signaling EAG in RSVP is not addressed in this document. This
document does not preclude addressing this in the future should it be
deemed necessary.
4. Security Considerations
This extension adds no new security considerations. This extension adds no new security considerations.
5. IANA Considerations 4. IANA Considerations
This document requests a sub-TLV allocation in both OSPF and ISIS. This document requests a sub-TLV allocation in both OSPF and ISIS.
For OSPF, the name space is "Types for sub-TLVs of TE Link TLV (Value For OSPF, the name space is "Types for sub-TLVs of TE Link TLV (Value
2)" in the "Open Shortest Path First (OSPF) Traffic Engineering 2)" in the "Open Shortest Path First (OSPF) Traffic Engineering
TLVs". For ISIS, it is "Sub-TLVs for TLV 22, 141, and 222" in the TLVs".
"IS-IS TLV Codepoints" registry. For IS-IS the value should be
marked 'y' for Sub-TLVs 22, 141 and 222; this is identical to the
allocation for the Administrative Group sub-TLV (value 3). In both
registries the first free value should be assigned. As of this
writing, that's 26 in the OSPF registry and 14 in the IS-IS registry.
6. Acknowledgements For ISIS, it is "Sub-TLVs for TLV 22, 141, and 222" in the "IS-IS TLV
Codepoints" registry. For IS-IS the value should be marked 'y' for
Sub-TLVs 22, 141 and 222; this is identical to the allocation for the
Administrative Group sub-TLV (value 3).
Thanks to Santiago Alvarez, Rohit Gupta, Liem Nguyen, Tarek Saad, and In both registries the first free value should be assigned. As of
Robert Sawaya for their review and comments. this writing, that's 26 in the OSPF registry and 14 in the IS-IS
registry. The Sub-TLV should be caled "Extended Administrative
Group".
7. References 5. Acknowledgements
7.1. Normative References Thanks to Santiago Alvarez, Rohit Gupta, Liem Nguyen, Tarek Saad,
Robert Sawaya, Andy Malis, Les Ginsberg and Adrian Farrel for their
review and comments.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001. Tunnels", RFC 3209, December 2001.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September (TE) Extensions to OSPF Version 2", RFC 3630, September
2003. 2003.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008. Engineering", RFC 5305, October 2008.
7.2. Informative References [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March
2009.
6.2. Informative References
[RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J. [RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
McManus, "Requirements for Traffic Engineering Over MPLS", McManus, "Requirements for Traffic Engineering Over MPLS",
RFC 2702, September 1999. RFC 2702, September 1999.
Author's Address Author's Address
Eric Osborne Eric Osborne
Email: eric.osborne@notcom.com Email: eric.osborne@notcom.com
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