MPLS Working Group Z. Ali
G. Swallow
Internet Draft Cisco Systems, Inc.
R. Aggarwal
Juniper Networks
Intended status: Standard Track October 26, 2009
Expires: April 25, 2010
Non PHP Behavior and out-of-band mapping for RSVP-TE LSPs
draft-ietf-mpls-rsvp-te-no-php-oob-mapping-03.txt
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Abstract
There are many deployment scenarios which require Egress LSR to
receive binding of the RSVP-TE LSP to an application, and payload
identification, using some "out-of-band" (OOB) mechanism. This
document proposes protocol mechanisms to address this
requirement. The procedures described in this document are
equally applicable for point-to-point (P2P) and point-to-
multipoint (P2MP) LSPs.
Conventions used in this document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
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-2119 0.
Table of Contents
1. Introduction...............................................2
2. RSVP-TE signaling extensions...............................3
2.1. Signaling non-PHP behavior............................3
2.2. Signaling OOB Mapping Indication......................4
2.3. Relationship between OOB and non-PHP flags............6
2.4. Egress Procedure for label binding....................6
3. Security Considerations....................................6
4. IANA Considerations........................................6
4.1. Attribute Flags for LSP_ATTRIBUTES object.............6
5. Acknowledgments............................................7
6. References.................................................7
6.1. Normative References..................................7
6.2. Informative References................................8
Copyright Notice..............................................8
Legal.........................................................9
1. Introduction
When RSVP-TE is used for applications like MVPN [MVPN] and VPLS
[VPLS], an Egress LSR receives the binding of the RSVP-TE LSP to
an application, and payload identification, using an "out-of-
band" (OOB) mechanism (e.g., using BGP). In such cases, the
Egress LSR cannot make correct forwarding decision until such OOB
mapping information is received. Furthermore, in order to apply
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the binding information, the Egress LSR needs to identify the
incoming LSP. Therefore, non Penultimate Hop Popping (non-PHP)
behavior is required at the Egress LSR to apply OOB mapping.
There are other applications that require non-PHP behavior. When
RSVP-TE P2MP LSPs are used to carry IP multicast traffic non-PHP
behavior enables a leaf LSR to identify the P2MP TE LSP, on which
traffic is received. Hence the egress LSR can determine whether
traffic is received on the expected P2MP LSP and discard traffic
that is not received on the expected P2MP LSP. Non-PHP behavior
is also required to determine the context of upstream assigned
labels when the context is a MPLS LSP. Non-PHP behavior may also
be required for MPLS-TP LSPs [MPLS-TP-Framework].
This document defines two new flags in the Attributes Flags TLV
of the LSP_ATTRIBUTES object defined in [RFC5420]: one flag for
communication of non-PHP behavior, and one flag to indicate that
the binding of the LSP to an application and payload identifier
(payload-Id) needs to be learned via an out-of-band mapping
mechanism.
The procedures described in this document are equally applicable
for P2P and P2MP LSPs. Specification of the OOB communication
mechanism(s) is beyond the scope of this document.
2. RSVP-TE signaling extensions
This section describes the signaling extensions required to
address the above-mentioned requirements.
2.1. Signaling non-PHP behavior
In order to request non-PHP behavior for RSVP-TE LSP, this
document defines a new flag in the Attributes Flags TLV of the
LSP_ATTRIBUTES object defined in [RFC5420]:
Bit Number 6 (TBD): non-PHP behavior desired flag.
In order to indicate to the Ingress LSR that the Egress LSR
recognizes the "non-PHP behavior desired flag", the following new
bit is defined in the Flags field of the Record Route object
(RRO) Attributes subobject:
Bit Number 6 (TBD): Non-PHP behavior acknowledgement flag.
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An Ingress LSR sets the non-PHP behavior desired flag to signal
the egress LSRs SHOULD assign non-NULL label for the LSP being
signaled. This flag MUST NOT be modified by any other LSRs in
the network. LSRs other than the Egress LSRs SHOULD ignore this
flag.
If an egress LSR receiving the Path message, supports the
LSP_ATTRIBUTES object and the Attributes Flags TLV, and also
recognizes the "non-PHP behavior desired flag", it MUST allocate
a non-NULL local label. The egress LSR MUST also set the "Non-PHP
behavior acknowledgement flag" in the Flags field of the RRO
Attribute subobject.
If the egress LSR supports the LSP_ATTRIBUTES object but does not
recognize the Attributes Flags TLV, or supports the TLV as well
but does not recognize this particular flag, then it SHOULD
simply ignore the above request.
An ingress LSR requesting non-PHP behavior MAY examine "Non-PHP
behavior acknowledgement flag" in the Flags field of the RRO
Attribute subobject and MAY send a Path Tear if the Egress
has not set the "Non-PHP behavior acknowledgement flag". An
ingress LSR requesting non-PHP behavior MAY also examine the
label value corresponding to the Egress LSR(s) in the RRO, and
MAY send a Path Tear if the Egress has assigns a Null label
value.
2.2. Signaling OOB Mapping Indication
This document defines a single flag to indicate that the normal
binding mechanism of an RSVP session is overridden. The actual
out of band mappings are beyond the scope of this document. The
flag is carried in the Attributes Flags TLV of the LSP_ATTRIBUTES
object defined in [RFC5420] and is defined as follows:
Bit Number 7 (TBD): OOB mapping indication flag.
In order to indicate to the Ingress LSR that the Egress LSR
recognizes the "OOB mapping indication flag", the following new
bit is defined in the Flags field of the Record Route object
(RRO) Attributes subobject:
Bit Number 7 (TBD): OOB mapping acknowledgement flag.
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An Ingress LSR sets the OOB mapping indication flag to signal the
Egress LSR that binding of RSVP-TE LSP to an application and
payload identification is being signaled out of band. This flag
MUST NOT be modified by any other LSRs in the network. LSRs other
than the Egress LSRs SHOULD ignore this flag.
When an egress LSR which supports the "OOB mapping indication
flag", receives a Path message with that flag set, the egress LSR
MUST set the "OOB mapping acknowledgement flag" in the Flags
field of the RRO Attribute subobject. The rest of the RSVP
signaling proceeds as normal. However, the LSR MUST have
received the OOB mapping before accepting traffic on the LSP.
This implies that the egress LSR MUST NOT setup forwarding state
for the LSP before it receives the OOB mapping.
Note that the payload information SHOULD be supplied by the OOB
mapping. If the egress LSR receives the payload information from
OOB mapping then the LSR MUST ignore L3PID in the Label Request
Object [RFC3209].
If the egress LSR supports the LSP_ATTRIBUTES object but does not
recognize the Attributes Flags TLV, or supports the TLV as well
but does not recognize this particular flag, then it SHOULD
simply ignore the above request.
An ingress LSR requesting OOB mapping MAY examine "OOB mapping
acknowledgement flag" in the Flags field of the RRO Attribute
subobject and MAY send a Path Tear to the Egress which has not
set the "OOB mapping acknowledgement flag".
In deploying applications where Egress LSR receives the binding
of the RSVP-TE LSP to an application, and payload identification,
using OOB mechanism, it is important to recognize that OOB
mapping is sent asynchronously w.r.t. signaling of RSVP-TE LSP.
Egress LSR only installs forwarding state for the LSP after it
receives the OOB mapping. In deploying applications using OOB
mechanism, ingress LSR may need to know when egress is properly
setup for forwarding (i.e., has received OOB mapping). How
ingress LSR determines that LSR is properly setup for forwarding
at the Egress LSR is beyond the scope of this document.
Nonetheless, if OOB mapping is not received by the egress LSR
within a reasonable time, a procedure to tear down the LSP is
defined in section 2.4.
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2.3. Relationship between OOB and non-PHP flags
Non-PHP behavior desired and OOB mapping indication flags can
appear and be processed independently of each other. However, as
mentioned earlier, in the context of application discussed in
this draft, OOB mapping require non-PHP behavior. An Ingress LSR
requesting OOB mapping MAY also set non-PHP behavior desired flag
in the LSP_ATTRIBUTES object in the Path message.
2.4. Egress Procedure for label binding
RSVP-TE signaling completion and the OOB mapping information
reception happen asynchronously at the Egress. As mentioned in
Section 2, Egress waits for the OOB mapping before accepting
traffic on the LSP.
In order to avoid unnecessary use of the resources and possible
block-holing of traffic, if the OOB mapping information is not
received within a reasonable time, Egress MAY trigger a Path
Error message with the error code/sub-code "Notify Error/ no OOB
mapping received" for all affected LSPs. If available, and where
notify requests were included when the LSPs were initially setup,
Notify messages (as defined in [RFC3473]) MAY also be used for
delivery of this information to the Ingress LSR. An Egress LSR
MAY implement a cleanup timer for this purpose. The time-out
value is a local decision at the Egress, with a RECOMMENDED
default value of 60 seconds.
3. Security Considerations
This document does not introduce any new security issues above
those identified in [RFC3209], [RFC5420] and [RFC4875].
4. IANA Considerations
4.1. Attribute Flags for LSP_ATTRIBUTES object
The following new flags are being defined for the Attributes
Flags TLV in the LSP_ATTRIBUTES object. The numeric values are
to be assigned by IANA.
o Non-PHP behavior desired flag - Bit Number 6 (Suggested
value).
o OOB mapping indication flag - Bit Number 7 (Suggested value).
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These flags are only to be used in the Attributes Flags TLV on a
Path message. These flags have corresponding new flags to be used
in the RRO Attributes subobject. As per RFC5420 [RFC5420], the
bit numbering in the Attribute Flags TLV and the RRO Attributes
subobject is identical. That is, the same attribute is indicated
by the same bit in both places. Specifically, the numeric values
for the corresponding new flags to be used in the RRO Attributes
subobject are to be assigned by IANA.
o OOB mapping acknowledgement flag - Bit Number 6 (Suggested
value).
o Non-PHP behavior acknowledgement flag - Bit Number 7
(Suggested value).
For Error Code = 25 "Notify Error" (see [RFC3209]) the following
sub-code is defined.
Sub-code Value
-------- -----
No OOB mapping received 12 (TBD)
5. Acknowledgments
The authors would like to thank Yakov Rekhter for his suggestions
on the draft.
6. References
6.1. Normative References
[RFC5420] A. Farrel, D. Papadimitriou, J. P. Vasseur and A.
Ayyangar, "Encoding of Attributes for Multiprotocol
Label Switching (MPLS) Label Switched Path (LSP)
Establishment Using RSVP-TE", RFC 5420, February 2006.
[RFC3209] D. Awduche, L. Berger, D. Gan, T. Li, V. Srinivasan,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC4875] R. Aggarwal, D. Papadimitriou, S. Yasukawa, et al,
"Extensions to RSVP-TE for Point-to-Multipoint TE
LSPs", RFC 4875.
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[RFC3473] L. Berger, Editor, "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
3473, January 2003.
6.2. Informative References
[MVPN] E. Rosen, R. Aggarwal et al, "Multicast in MPLS/BGP IP
VPNs", draft-ietf-l3vpn-2547bis-mcast-08.txt, work in
progress.
[VPLS] R. Aggarwal, et al, "Propagation of VPLS IP Multicast
Group Membership Information", draft-raggarwa-l2vpn-
vpls-mcast-ctrl-00.txt, work in progress.
[MPLS-TP-Framework] M. Bocci, S. Bryant, et al, "A Framework for
MPLS in Transport Networks",
draft-ietf-mpls-tp-framework-06, work in progress.
Author's Addresses
Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com
George Swallow
Cisco Systems, Inc.
Email: swallow@cisco.com
Rahul Aggarwal
Juniper Networks
rahul@juniper.net
Copyright Notice
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This document is subject to BCP 78 and the IETF Trust's Legal
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publication of this document
(http://trustee.ietf.org/license-info). Please review these
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