TEAS Working Group X. Zhang, Ed.
Internet-Draft Huawei Technologies
Intended status: Standards Track V. Beeram, Ed.
Expires: September 14, 2017 Juniper Networks
I. Bryskin
Huawei Technologies
D. Ceccarelli
Ericsson
O. Gonzalez de Dios
Telefonica
March 13, 2017
Network Assigned Upstream-Label
draft-ietf-teas-network-assigned-upstream-label-05
Abstract
This document discusses a Generalized Multi-Protocol Label Switching
(GMPLS) Resource reSerVation Protocol with Traffic Engineering (RSVP-
TE) mechanism that enables the network to assign an upstream label
for a bidirectional LSP. This is useful in scenarios where a given
node does not have sufficient information to assign the correct
upstream label on its own and needs to rely on the downstream node to
pick an appropriate label.
Status of This Memo
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Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Unassigned Upstream Label . . . . . . . . . . . . . . . . . . 3
2.1. Processing Rules . . . . . . . . . . . . . . . . . . . . 3
2.2. Backwards Compatibility . . . . . . . . . . . . . . . . . 4
3. Use-Case: Wavelength Setup for IP over Optical Networks . . . 4
3.1. Initial Setup . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Wavelength Change . . . . . . . . . . . . . . . . . . . . 6
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
The Generalized Multi-Protocol Label Switching (GMPLS) Resource
reSerVation Protocol with Traffic Engineering (RSVP-TE) extensions
for setting up a bidirectional LSP are specified in [RFC3473]. The
bidirectional LSP setup is indicated by the presence of an
UPSTREAM_LABEL Object in the PATH message. As per the existing setup
procedure outlined for a bidirectional LSP, each upstream node must
allocate a valid upstream label on the outgoing interface before
sending the initial PATH message downstream. However, there are
certain scenarios where it is not desirable or possible for a given
node to pick the upstream label on its own. This document defines
the protocol mechanism to be used in such scenarios. This mechanism
enables a given node to offload the task of assigning the upstream
label for a given bidirectional LSP to nodes downstream in the
network. It is meant to be used only for bidirectional LSPs that
assign symmetric labels at each hop along the path of the LSP.
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1.1. Requirements Language
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 [RFC2119].
2. Unassigned Upstream Label
This document proposes the use of a special label value -
"0xFFFFFFFF" (for a 4-byte label) - to indicate an Unassigned
Upstream Label. Similar "all-ones" patterns are expected to be used
for labels of other sizes. The presence of this value in the
UPSTREAM_LABEL object of a PATH message indicates that the upstream
node has not assigned an upstream label on its own and has requested
the downstream node to provide a label that it can use in both
forward and reverse directions. The presence of this value in the
UPSTREAM_LABEL object of a PATH message MUST also be interpreted by
the receiving node as a request to mandate symmetric labels for the
LSP.
2.1. Processing Rules
The Unassigned Upstream Label is used by an upstream node when it is
not in a position to pick the upstream label on its own. In such a
scenario, the upstream node sends a PATH message downstream with an
Unassigned Upstream Label and requests the downstream node to provide
a symmetric label. If the upstream node desires to make the
downstream node aware of its limitations with respect to label
selection, it MUST specify a list of valid labels via the LABEL_SET
object as specified in [RFC3473].
In response, the downstream node picks an appropriate symmetric label
and sends it via the LABEL object in the RESV message. The upstream
node would then start using this symmetric label for both directions
of the LSP. If the downstream node cannot pick the symmetric label,
it MUST issue a PATH-ERR message with a "Routing Problem/Unacceptable
Label Value" indication.
The upstream node will continue to signal the Unassigned Upstream
Label in the PATH message even after it receives an appropriate
symmetric label in the RESV message. This is done to make sure that
the downstream node would pick a different symmetric label if and
when it needs to change the label at a later point in time. If the
upstream node receives an unacceptable changed label, then the error
procedure defined in [RFC3473] MUST be followed.
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+----------+ +------------+
---| Upstream |--------------------| Downstream |---
+----------+ +------------+
PATH
Upstream Label (Unassigned)
Label-Set (L1, L2 ... Ln)
------------------->
RESV
Label (Assigned - L2)
<-------------------
Unassigned UPSTREAM_LABEL
Figure 1
2.2. Backwards Compatibility
If the downstream node is running an implementation that doesn't
support the semantics of an Unassigned UPSTREAM LABEL, it will either
(a) reject the special label value and generate an error as specified
in Section 3.1 of [RFC3473] or (b) accept it and treat it as a valid
label.
If the behavior that is exhibited is (a), then there are obviously no
backwards compatibility concerns. If there is some existing
implementation that exhibits the behavior in (b), then there could be
some potential issues. However, at the time of publication, there is
no documented evidence of any existing implementation that uses the
"all-ones" bit pattern as a valid label. Thus, it is safe to assume
that the behavior in (b) will never be exhibited.
3. Use-Case: Wavelength Setup for IP over Optical Networks
Consider the network topology depicted in Figure 2. Nodes A and B
are client IP routers that are connected to an optical WDM transport
network. F and I represent WDM nodes. The transponder sits on the
router and is directly connected to the add-drop port on a WDM node.
The optical signal originating on "Router A" is tuned to a particular
wavelength. On "WDM-Node F", it gets multiplexed with optical
signals at other wavelengths. Depending on the implementation of
this multiplexing function, it may not be acceptable to have the
router send signal into the optical network unless it is at the
appropriate wavelength. In other words, having the router send
signal with a wrong wavelength may adversely impact existing optical
trails. If the clients do not have full visibility into the optical
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network, they are not in a position to pick the correct wavelength
up-front.
The rest of this section examines how the protocol mechanism proposed
in this document allows the optical network to select and communicate
the correct wavelength to its clients.
3.1. Initial Setup
+---+ /-\ /-\ +---+
| A |----------------( F ) ~~~~~~~~~ ( I )----------------| B |
+---+ \-/ \-/ +---+
PATH
Upstream Label (Unassigned/0xFFFFFFFF)
--------------------->
-- ~~ -- ~~ -->
PATH
-------------------->
RESV
<--------------------
<-- ~~ -- ~~ --
RESV
Label (Assigned)
<---------------------
Initial Setup Sequence
Figure 2
Steps:
o "Router A" does not have enough information to pick an appropriate
client wavelength. It sends a PATH message downstream requesting
the network to assign an appropriate symmetric label for its use.
Since the client wavelength is unknown, the laser is off at the
ingress client.
o The downstream node (Node F) receives the PATH message, chooses
the appropriate wavelength values and forwards them in appropriate
label fields to the egress client ("Router B")
o "Router B" receives the PATH message, turns the laser ON and tunes
it to the appropriate wavelength (received in the UPSTREAM_LABEL/
LABEL_SET of the PATH) and sends out a RESV message upstream.
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o The RESV message received by the ingress client carries a valid
symmetric label in the LABEL object. "Router A" turns on the
laser and tunes it to the wavelength specified in the network
assigned symmetric LABEL.
For cases where the egress-node relies on RSVP signaling to determine
exactly when to start using the LSP, implementations may choose to
integrate the above sequence with any of the existing graceful setup
procedures:
o "RESV-CONF" setup procedure ([RFC2205])
o 2-step "ADMIN STATUS" based setup procedure ("A" bit set in the
first step; "A" bit cleared when the LSP is ready for use).
([RFC3473])
3.2. Wavelength Change
After the LSP is set up, the network may decide to change the
wavelength for the given LSP. This could be for a variety of reasons
- policy reasons, restoration within the core, preemption etc.
In such a scenario, if the ingress client receives a changed label
via the LABEL object in a RESV modify, it retunes the laser at the
ingress to the new wavelength. Similarly, if the egress client
receives a changed label via UPSTREAM_LABEL/LABEL_SET in a PATH
modify, it retunes the laser at the egress to the new wavelength.
4. Acknowledgements
The authors would like to thank Adrian Farrel and Chris Bowers for
their inputs.
5. Contributors
John Drake
Juniper Networks
Email: jdrake@juniper.net
Gert Grammel
Juniper Networks
Email: ggrammel@juniper.net
Pawel Brzozowski
ADVA Optical Networking
Email: pbrzozowski@advaoptical.com
Zafar Ali
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Cisco Systems, Inc.
Email: zali@cisco.com
6. IANA Considerations
This document makes no requests for IANA action.
7. Security Considerations
This document defines a special label value to be carried in the
UPSTREAM_LABEL object of a PATH message. This special label value is
used to enable the function of requesting network assignment of an
upstream label. The changes proposed in this document pertain to the
semantics of a specific field in an existing RSVP object and the
corresponding procedures. Thus, there are no new security
implications raised by this document and the security considerations
put together by [RFC3473] still applies.
For a general discussion on MPLS and GMPLS related security issues,
see the MPLS/GMPLS security framework [RFC5920].
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
September 1997, <http://www.rfc-editor.org/info/rfc2205>.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC3473, January 2003,
<http://www.rfc-editor.org/info/rfc3473>.
8.2. Informative References
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<http://www.rfc-editor.org/info/rfc5920>.
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Authors' Addresses
Xian Zhang (editor)
Huawei Technologies
Email: zhang.xian@huawei.com
Vishnu Pavan Beeram (editor)
Juniper Networks
Email: vbeeram@juniper.net
Igor Bryskin
Huawei Technologies
Email: igor.bryskin@huawei.com
Daniele Ceccarelli
Ericsson
Email: daniele.ceccarelli@ericsson.com
Oscar Gonzalez de Dios
Telefonica
Email: ogondio@tid.es
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