MPLS Working Group Z. Ali
G. Swallow
Internet Draft Cisco Systems, Inc.
R. Aggarwal
Juniper Networks
Intended status: Standard Track April 12, 2011
Expires: October 11, 2011
Non PHP Behavior and out-of-band mapping for RSVP-TE LSPs
draft-ietf-mpls-rsvp-te-no-php-oob-mapping-06.txt
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Abstract
There are many deployment scenarios which require Egress Label
Switching Router (LSR) to receive binding of the Resource
ReserVation Protocol Traffic Engineered (RSVP-TE) Label Switched
Path (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
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 [RFC2119].
Table of Contents
1. Introduction...............................................3
2. RSVP-TE signaling extensions...............................3
2.1. Signaling non-PHP behavior............................3
2.2. Signaling OOB Mapping Indication......................5
2.3. Relationship between OOB and non-PHP flags............6
2.4. Egress Procedure for label binding....................6
3. Security Considerations....................................7
4. IANA Considerations........................................7
4.1. Attribute Flags for LSP_ATTRIBUTES object.............7
5. Acknowledgments............................................7
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6. References.................................................8
6.1. Normative References..................................8
6.2. Informative References................................8
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
the binding information, the Egress LSR needs to identify the
incoming LSP on which traffic is coming. Therefore, non
Penultimate Hop Popping (non-PHP) behavior is required 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 an RSVP-TE LSP, this
document defines a new flag in the Attributes Flags TLV of the
LSP_ATTRIBUTES object defined in [RFC5420]:
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Bit Number 6 (TBD): non-PHP behavior flag.
An Ingress LSR sets the "non-PHP behavior 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.
When signaling a P2MP LSP, a source node may wish to solicit
individual response to "non-PHP behavior flag" from the leaf
nodes. Given the constraints on how the LSP_ATTRIBUTES may be
carried in Path and Resv Messages according to RFC5420, in this
situation a source node MUST use a separate Path message for
each leaf.
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 flag", it MUST allocate a non-
NULL local label. The egress LSR MUST also include the
LSP_ATTRIBUTES object with "non-PHP behavior flag" set in the
Resv message. For this purpose, as defined in RFC5420, the
LSP_ATTRIBUTES object is placed in the flow descriptor and is
associated with the FILTER_SPEC object that precedes it.
If the egress LSR
- supports the LSP_ATTRIBUTES object but does not recognize the
Attributes Flags TLV; or
- supports the LSP_ATTRIBUTES object and recognize the Attributes
Flags TLV, but does not recognize "non-PHP behavior flag";
then it SHOULD silently ignore this request.
An ingress LSR requesting non-PHP behavior SHOULD examine Resv
message for presence of "Non-PHP behavior flag" in the
LSP_ATTRIBUTES object. An ingress LSR requesting non-PHP behavior
MAY send a Path Tear to the Egress which has not included the
LSP_ATTRIBUTES object in the Resv or which has included the
LSP_ATTRIBUTES object in Resv but has not set the "Non-PHP
behavior flag" in it. 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 to the Egress which
assigns a Null label value.
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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 flag.
An Ingress LSR sets the OOB mapping 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 signaling a P2MP LSP, a source node may wish to solicit
individual response to "OOB mapping flag" from the leaf nodes.
Given the constraints on how the LSP_ATTRIBUTES may be carried in
Path and Resv Messages according to RFC5420, in this situation a
source node MUST use a separate Path message for each leaf.
If an egress LSR receiving the Path message, supports the
LSP_ATTRIBUTES object and the Attributes Flags TLV, and also
recognizes the "OOB mapping flag", it MUST include the
LSP_ATTRIBUTES object with "OOB mapping flag" set in the Resv
message. For this purpose, as defined in RFC5420, the
LSP_ATTRIBUTES object is placed in the flow descriptor and is
associated with the FILTER_SPEC object that precedes it.
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
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- supports the LSP_ATTRIBUTES object and recognizes the
Attributes Flags TLV, but does not recognize the "OOB mapping
flag";
then it SHOULD silently ignore this request.
An ingress LSR requesting OOB mapping SHOULD examine Resv message
for presence of "OOB mapping flag" in in the LSP_ATTRIBUTES
object. An ingress LSR requesting OOB mapping MAY send a Path
Tear to the Egress which has not included the LSP_ATTRIBUTES
object in the Resv or which has included the LSP_ATTRIBUTES
object in Resv but has not set the " OOB mapping flag" in it.
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.
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 applications discussed in
this document, OOB mapping require non-PHP behavior. An Ingress
LSR requesting OOB mapping MAY also set "non-PHP behavior 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
black-holing of traffic, an Egress LSR MAY send a Path Error
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message if the OOB mapping information is not received within a
reasonable time. This Path Error message will include the error
code/sub-code "Notify Error/ no OOB mapping received" for all
affected LSPs. If notify request was included when the LSP was
initially setup, Notify message (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 [RFC2205], [RFC3209], [RFC3473], [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 flag - Bit Number 6 (Suggested value).
o OOB mapping flag - Bit Number 7 (Suggested value).
o These flags are to be used in the Attributes Flags TLV in both
Path and Resv messages.
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.
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6. References
6.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[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
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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
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