PCE Working Group S. Sivabalan
Internet-Draft C. Filsfils
Intended status: Standards Track S. Previdi
Expires: October 25, 2015 Cisco Systems, Inc.
J. Tantsura
Ericsson
J. Hardwick
Metaswitch Networks
M. Nanduri
Microsoft Corporation
April 23, 2015
Carrying Binding Label/Segment-ID in PCE-based Networks.
draft-sivabalan-pce-binding-label-sid-00.txt
Abstract
It is possible to associate a binding label to RSVP-TE signaled
Traffic Engineering Label Switching Path or binding Segment-ID (SID)
to Segment Routed Traffic Engineering path. Such a binding label/SID
can be used by an upstream node for steering traffic into the
appropriate TE path to enforce TE policies. This document proposes
an approach for reporting binding label/SID to Path Computation
Element (PCE) for supporting PCE-based Traffic Engineering policies.
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].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 25, 2015.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Path Binding TLV . . . . . . . . . . . . . . . . . . . . . . . 5
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
8. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
A PCE can compute Traffic Engineering paths (TE paths) through a
network that are subject to various constraints. Currently, TE paths
are either set up using the RSVP-TE signaling protocol or Segment
Routed (SR). We refer to such paths as RSVP-TE paths and SR-TE paths
respectively in this document.
Similar to assigning label to a Forwarding Equivalence Class (FEC)
via Label Distribution Protocol (LDP), a binding label can be
assigned to a RSVP-TE LSP. If the topmost label of an incoming
packet is the binding label, the packet is steered onto the RSVP-TE
LSP. As such, any upstream node can use binding labels to steer the
packets that it originates to appropriate TE LSPs to enforce TE
policy. Similarly, a binding SID (see
[I-D.ietf-isis-segment-routing-extensions] and
[I-D.ietf-ospf-segment-routing-extensions]) can be used to enforce TE
policy with SR-TE path. Note that if an SR-TE path is represented as
a forwarding-adjacency, then the corresponding adjacency SID can be
used as the binding SID. In such case, the path is advertised using
the routing protocols as described in [RFC5440]. The binding SID
provides an alternate mechanism without additional overhead on
routing protocols.
[RFC5440] describes the Path Computation Element Protocol (PCEP) for
communication between a Path Computation Client (PCC) and a PCE or
between a pair of PCEs.[I-D.ietf-pce-stateful-pce] specifies
extension to PCEP that allows a PCC to delegate its LSPs to a PCE.
The PCE can then update the state of LSPs delegated to it.
[I-D.ietf-pce-pce-initiated-lsp] specifies a mechanism allowing a PCE
to dynamically instantiate an LSP on a PCC by sending the path and
characteristics of the LSP. The PCEP extension to setup and maintain
SR-TE paths is specified in [I-D.ietf-pce-segment-routing].
Binding label/SID has local significance to the ingress node of the
corresponding TE path. When a stateful PCE is deployed for setting
up TE paths, it may be desirable to report the binding label or SID
to the PCE for the purpose of enforcing end-to-end TE policy. A
sample Data Center (DC) use-case is illustrated in the following
diagram. In the MPLS DC network, an SR LSP (without traffic
engineering) is established using a prefix SID advertised by BGP (see
[I-D.keyupate-idr-bgp-prefix-sid]). In IP/MPLS WAN, an SR-TE LSP is
setup using the PCE. The list of SIDs of the SR-TE LSP is {A, B, C,
D}. The gateway node 1 (which is the PCC) allocates a binding SID X
and reports it to the PCE. In order for the access node to steer the
traffic over the SR-TE LSP, the PCE passes the SID stack {Y, X} where
Y is the prefix SID of the gateway node-1 to the access node. In the
absence of the binding SID X, the PCE should pass the SID stack {Y,
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A, B, C, D} to the access node. This example also illustrates the
additional benefit of using the binding SID to reduce the number of
SIDs imposed on the access nodes with a limited forwarding capacity.
SID stack
{Y, X} +-----+
_ _ _ _ _ _ _ _ _ _ _ _ _ _| PCE |
| +-----+
| ^
| | Binding
| .-----. | SID (X) .-----.
| ( ) | ( )
V .--( )--. | .--( )--.
+------+ ( ) +-------+ ( ) +-------+
|Access|_( MPLS DC Network )_|Gateway|_( IP/MPLS WAN )_|Gateway|
| Node | ( ==============> ) |Node-1 | ( ================> ) |Node-2 |
+------+ ( SR path ) +-------+ ( SR-TE path ) +-------+
'--( )--' Prefix '--( )--'
( ) SID of ( )
'-----' Node-1 '-----'
is Y SIDs for SR-TE LSP:
{A, B, C, D}
Figure 1: A sample Use-case of Binding SID
In this document, we introduce a new OPTIONAL TLV that a PCC can use
in order to report the binding label associated with a TE LSP. This
TLV is intended for TE LSPs established using RSVP-TE, SR, or any
other future method. Also, in the case of SR-TE LSPs, the TLV can
carry an MPLS label binding (for SR-TE path with MPLS data-plane) or
a binding SID (e.g., IPv6 address for SR-TE paths with IPv6 data-
plane). However, use of this TLV for non-MPLS label binding will be
described in separate document(s).
2. Terminology
The following terminologies are used in this document:
LER: Label Edge Router.
LSP: Label Switched Path.
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LSR: Label Switching Router.
PCC: Path Computation Client.
PCE: Path Computation Element
PCEP: Path Computation Element Protocol.
SID: Segment ID.
SR: Segment Routing.
TLV: Type, Length, and Value.
3. Path Binding TLV
The new optional TLV is called "TE-PATH-BINDING TLV" whose format is
shown in the diagram below is defined to carry binding label or SID
for a TE path. This TLV is associated with the LSP object specified
in ([I-D.ietf-pce-stateful-pce]). The type of this TLV is to be
allocated by IANA.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Binding Type (BT) | Binding Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Binding Value (continued) (variable length) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: TE-PATH-BINDING TLV
TE-PATH-BINDING TLV is a generic TLV such that it is able to carry
MPLS label binding as well as other types of future bindings (e.g.,
IPv6 SR path). The one octet Binding Type (BT) field identifies the
type of binding included in the TLV. This document specifies the
following BT value:
o BT = 0: MPLS label (default).
4. Operation
The binding value is allocated by PCC and reported to PCE via PCRpt
message. If a PCE does not recognize the TE-PATH-BINDING TLV, it
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MUST ignore the TLV in accordance with ([RFC5440]). If a PCE
recognizes the TLV but does not support the TLV, it MUST send PCErr
with Error-Type = 2 (Capability not supported).
If a TE-PATH-BINDING TLV is absent in PCRpt message, PCE MUST assume
that the corresponding LSP does not have any binding. If there are
more than one PATH-BINDING TLVs, only the first TLV MUST be processed
and the rest MUST be silently ignored. If PCE recognizes an invalid
binding value (e.g., label value from the reserved label space when
MPLS label binding is used), it MUST send the PCE error message with
Error-Type = 10 ("Reception of an invalid object") and Error Value =
TBD ("Bad label value") as specified in
[I-D.ietf-pce-segment-routing].
If a PCC receives TE-PATH-BINDING TLV in any message, it MUST close
the corresponding PCEP session with the reason "Reception of a
malformed PCEP message" according ([RFC5440]). Similarly, if a PCE
receives a TE-PATH-BINDING TLV in any message other than a PCRpt or
if the TE-PATH-BINDING TLV is associated with any object other than
LSP object, the PCE MUST close the corresponding PCEP session with
the reason "Reception of a malformed PCEP message" according
([RFC5440]).
If a PCC wants to withdraw or modify a previously reported binding
value, it MUST send a PCRpt message without any TE-PATH-BINDING TLV
and with the TE-PATH-BINDING TLV containing the new binding value
respectively.
5. Security Considerations
No additional security measure is required.
6. IANA Considerations
IANA is requested to allocate a new TLV type (recommended value is
31)for TE-PATH-BINDING TLV specified in this document.
This document requests that a registry is created to manage the value
of the Binding Type field in the TE-PATH-BINDING TLV.
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Value Description Reference
0 MPLS Label This document
7. Acknowledgements
8. Normative References
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
Extensions for Segment Routing",
draft-ietf-isis-segment-routing-extensions-03 (work in
progress), October 2014.
[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing",
draft-ietf-ospf-segment-routing-extensions-04 (work in
progress), February 2015.
[I-D.ietf-pce-pce-initiated-lsp]
Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
Extensions for PCE-initiated LSP Setup in a Stateful PCE
Model", draft-ietf-pce-pce-initiated-lsp-04 (work in
progress), April 2015.
[I-D.ietf-pce-segment-routing]
Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E.,
Lopez, V., Tantsura, J., Henderickx, W., and J. Hardwick,
"PCEP Extensions for Segment Routing",
draft-ietf-pce-segment-routing-03 (work in progress),
April 2015.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
Extensions for Stateful PCE",
draft-ietf-pce-stateful-pce-11 (work in progress),
April 2015.
[I-D.keyupate-idr-bgp-prefix-sid]
Patel, K., Ray, S., Previdi, S., and C. Filsfils, "Segment
Routing Prefix SID extensions for BGP",
draft-keyupate-idr-bgp-prefix-sid-01 (work in progress),
April 2015.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440,
March 2009.
Authors' Addresses
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: msiva@cisco.com
Clarence Filsfils
Cisco Systems, Inc.
Pegasus Parc
De kleetlaan 6a, DIEGEM BRABANT 1831
BELGIUM
Email: cfilsfil@cisco.com
Stefano Previdi
Cisco Systems, Inc.
Via Del Serafico, 200
Rome, Rome 00142
Italy
Email: sprevidi@cisco.com
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Jeff Tantsura
Ericsson
300 Holger Way
San Jose, CA 95134
USA
Email: jeff.tantsura@ericsson.com
Jonathan Hardwick
Metaswitch Networks
100 Church Street
Enfield, Middlesex
UK
Email: Jonathan.Hardwick@metaswitch.com
Mohan Nanduri
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
USA
Email: mnanduri@microsoft.com
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