Internet DRAFT - draft-chen-pce-label-x-domains
draft-chen-pce-label-x-domains
PCE Working Group H. Chen
Internet-Draft Futurewei
Intended status: Standards Track A. Liu
Expires: 13 July 2024 Ciena
M. Toy
Verizon
V. Liu
10 January 2024
Extensions to PCEP for Distributing Label Cross Domains
draft-chen-pce-label-x-domains-18
Abstract
This document specifies extensions to PCEP for distributing labels
crossing domains for an inter-domain Point-to-Point (P2P) or Point-
to-Multipoint (P2MP) Traffic Engineering (TE) Label Switched Path
(LSP).
Status of This Memo
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Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Conventions Used in This Document . . . . . . . . . . . . . . 3
4. Label Distribution . . . . . . . . . . . . . . . . . . . . . 4
4.1. An Exmaple . . . . . . . . . . . . . . . . . . . . . . . 4
5. Extensions to PCEP . . . . . . . . . . . . . . . . . . . . . 5
5.1. RP Object Extension . . . . . . . . . . . . . . . . . . . 5
5.2. Label Object . . . . . . . . . . . . . . . . . . . . . . 6
5.3. LSP Tunnel Object . . . . . . . . . . . . . . . . . . . . 7
5.4. Request Message Extension . . . . . . . . . . . . . . . . 9
5.5. Reply Message Extension . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7.1. Request Parameter Bit Flags . . . . . . . . . . . . . . . 9
8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
After a path crossing multiple domains is computed, an inter-domain
Traffic Engineering (TE) Label Switched Path (LSP) tunnel may be set
up along the path by a number of tunnel central controllers (TCCs).
Each of the domains through which the path goes may be controlled by
a tunnel central controller (TCC), which sets up the segment of the
TE LSP tunnel in the domain. When the TCC sets up the segment of the
TE LSP tunnel in its domain that is not a domain containing the tail
end of the tunnel, it needs a label and an interface from a
downstream domain, which is next to it along the path.
This document specifies extensions to PCEP for distributing a label
and an interface from a domain to its upstream domain along the path
for the TE LSP tunnel crossing multiple domains.
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2. Terminology
ABR: Area Border Router. Routers used to connect two IGP areas
(areas in OSPF or levels in IS-IS).
ASBR: Autonomous System Border Router. Routers used to connect
together ASes via inter-AS links.
Boundary Node (BN): a boundary node is either an ABR in the context
of inter-area Traffic Engineering or an ASBR in the context of inter-
AS Traffic Engineering.
Entry BN of domain(n): a BN connecting domain(n-1) to domain(n) along
a determined sequence of domains.
Exit BN of domain(n): a BN connecting domain(n) to domain(n+1) along
a determined sequence of domains.
Inter-area TE LSP: A TE LSP that crosses an IGP area boundary.
Inter-AS TE LSP: A TE LSP that crosses an AS boundary.
LSP: Label Switched Path.
LSR: Label Switching Router.
PCC: Path Computation Client. Any client application requesting a
path computation to be performed by a Path Computation Element.
PCE: Path Computation Element. An entity (component, application, or
network node) that is capable of computing a network path or route
based on a network graph and applying computational constraints.
PCE(i) is a PCE with the scope of domain(i).
TED: Traffic Engineering Database.
This document uses terminologies defined in RFC5440.
3. 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 RFC2119.
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4. Label Distribution
The Label Distribution may be provided by the PCE-based path
computation. A PCE responsible for a domain computes a path segment
for the domain, which is from an entry boundary to an exit boundary
(or an egress) node of the domain. The PCE gets an label from the
entry boundary node and adds an label object containing the label and
an interface as the incoming interface of the label in the reply
message to be sent to the requesting PCC (or another PCE).
When a PCE or PCC receives a reply message containing an label
object, it removes the object from the message. The PCE may store
the information in the label object or send the information to
another component such as a Tunnel Central Controller (TCC).
4.1. An Exmaple
Figure 1 below illustrates a simple two-AS topology. There is a PCE
responsible for the path computation in each AS. A path computation
is requested from the Tunnel Central Controller (TCC), acting as the
PCC, which sends the path computation request to PCE-1.
PCE-1 is unable to compute an end-to-end path and invokes PCE-2
(possibly using the techniques described in [RFC5441]). PCE-2
computes a path segment from entry boundary node ASBR-2 of the right
domain to the egress as {ASBR-2, C, D, Egress}.
In addition to placing this path segment in the reply message to PCE-
1, PCE-2 gets an label from the entry boundary node ASBR-2 and adds
an label object containing the label with the interface between
ASBR-1 and ASBR-2 into the reply message.
------------------------------- ------------------------------
| ------- | | ------- |
| +-->| PCE-1 |<---------+--+-->| PCE-2 | |
| | ------- | | ------- |
| v | | ^ |
| ----- | | | |
| | TCC | | | | |
| | PCC | | | | |
| ----- | | v |
| ------- - - ------ | | ------ - - ------ |
| |Ingress|--|A|--|B|--|ASBR-1|-+--+-|ASBR-2|--|C|--|D|--|Egress| |
| ------- - - ------ | | ------ - - ------ |
| | | |
------------------------------- ------------------------------
Figure 1: Example of Label Distribution
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When PCE-1 receives the reply message containing the label object
from PCE-2, it removes the object from the message. PCE-1 may store
the information in the label object or send the information to
another component such as a Tunnel Central Controller (TCC). TCC may
set up the segment of the LSP tunnel from Ingress to ASBR-2 using the
label with the interface in the label object from ASBR-2.
5. Extensions to PCEP
This section describes the extensions to PCEP for distributing labels
crossing domains for an inter-domain Point-to-Point (P2P) or Point-
to-Multipoint (P2MP) Traffic Engineering (TE) Label Switched Path
(LSP). The extensions include the definition of a new flag in the RP
object, tunnel information and label in a PCReq/PCRep message.
5.1. RP Object Extension
The following flags are added into the RP Object:
o L (Label distribution bit - 1 bit):
0: This indicates that this is not a PCReq/PCRep message
for distributing labels crossing domains.
1: This indicates that this is a PCReq or PCRep message
for distributing labels crossing domains.
o C (LSP tunnel Creation bit - 1 bit):
0: This indicates that this is not a PCReq/PCRep message for
creating the segment of the LSP tunnel.
1: This indicates that this is a PCReq/PCRep message for
creating the segment of the LSP tunnel in the domain
and distributing labels to its previous domain.
An L bit is added in the flag bits field of the RP object to tell a
receiver of a PCReq/PCRep message that the message is for
distributing labels crossing domains for an inter-domain LSP. The
IANA request is referenced in Section below (Request Parameter Bit
Flags) of this document.
The C bit is added in the flag bits field of the RP object to tell
the receiver of a PCReq/PCRep message that the message is for
creating the segment of the LSP tunnel in a domain and distributing
labels from this domain to its previous domain. The IANA request is
referenced in Section below (Request Parameter Bit Flags) of this
document.
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This L bit with the N bit defined in RFC6006 can indicate whether the
PCReq/PCRep message is for distributing labels for an MPLS TE P2P LSP
or an MPLS TE P2MP LSP.
o L = 1 and N = 0: This indicates that this is a PCReq/PCRep message
for distributing labels for a P2P LSP.
o L = 1 and N = 1: This indicates that this is a PCReq/PCRep message
for distributing labels for a P2MP LSP.
5.2. Label Object
The format of a label object body (Object-Type=2) is illustrated
below, which comprises a label and an optional node sub object. The
node sub object contains a boundary node IP address, from which the
label is allocated and distributed.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node IPv4/IPv6 sub object (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of the node IPv4 address sub object (Type=1) is as
follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type(1) | Length (8) | Node IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node IPv4 address (cont) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of the node IPv6 address sub object (Type=2) is
illustrated below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type(2) | Length (20) | Node IPv6 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Node IPv6 address (cont) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node IPv6 address (cont) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.3. LSP Tunnel Object
The LSP tunnel object contains the information that may be used to
identify an LSP tunnel. An LSP tunnel may be a P2P or P2MP LSP
tunnel. It may be an IPv4 or IPv6 LPS tunnel. Thus there are four
types of LSP tunnels: 1) P2P LSP IPv4 tunnel, 2) P2P LSP IPv6 tunnel,
3) P2MP LSP IPv4 tunnel, and 4) P2MP LSP IPv6 tunnel.
The format of the P2P LSP IPv4/6 tunnel object body is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P2P LSP Tunnel Egress IPv4/6 Address (4/16 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Tunnel ID (4/16 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Controller ID (4/16 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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o P2P LSP Tunnel Egress IPv4/6 Address:
IPv4/6 address of the egress of the tunnel.
o Tunnel ID:
A 16-bit identifier that is constant over the life of the tunnel.
o Extended Tunnel ID:
A 4/16-byte identifier that is constant over the life of the tunnel.
o LSP ID:
A 16-bit identifier to allow resources sharing.
o Controller ID:
A 4/16-byte identifier for the controller responsible for the head
segment of the tunnel.
The format of the P2MP LSP IPv4/6 tunnel object body is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P2MP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Tunnel ID (4/16 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Controller ID (4/16 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o P2MP ID:
A 32-bit number unique within the ingress of LSP tunnel.
o Tunnel ID:
A 16-bit identifier that is constant over the life of the tunnel.
o Extended Tunnel ID:
A 4/16-byte identifier that is constant over the life of the tunnel.
o LSP ID:
A 16-bit identifier to allow resources sharing.
o Controller ID:
A 16-byte identifier for the controller responsible for the head
segment of the tunnel.
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5.4. Request Message Extension
Figure below illustrates the format of a request message with a
optional LSP tunnel object:
<PCReq Message>::= <Common Header>
[<svec-list>]
<request-list>
<request-list>::=<request>[<request-list>]
<request>::= <RP> <END-POINTS> [<OF>] [<LSPA>] [<BANDWIDTH>]
[<metric-list>] [<RRO>[<BANDWIDTH>]] [<IRO>]
[<LOAD-BALANCING>]
[<LSP-tunnel>]
5.5. Reply Message Extension
Below is the format of a reply message with an optional Label object:
<PCReq Message>::= <Common Header>
<response-list>
<response-list>::=<response>[<response-list>]
<response>::= <RP>
[<NO-PATH>]
[<attribute-list>]
[<path-list>]
<path-list>::=<path>[<path-list>]
<path>::= <ERO><attribute-list>[<LSP-tunnel>][<Label>]
6. Security Considerations
The mechanism described in this document does not raise any new
security issues for the PCEP protocols.
7. IANA Considerations
This section specifies requests for IANA allocation.
7.1. Request Parameter Bit Flags
A new RP Object Flag has been defined in this document. IANA is
requested to make the following allocation from the "PCEP RP Object
Flag Field" Sub-Registry:
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Bit Description Reference
18 Label Distribution (L-bit) This I-D
19 LSP tunnel Creation (C-bit) This I-D
8. Acknowledgement
The author would like to thank people for their valuable comments on
this draft.
9. References
9.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC6006] Zhao, Q., Ed., King, D., Ed., Verhaeghe, F., Takeda, T.,
Ali, Z., and J. Meuric, "Extensions to the Path
Computation Element Communication Protocol (PCEP) for
Point-to-Multipoint Traffic Engineering Label Switched
Paths", RFC 6006, DOI 10.17487/RFC6006, September 2010,
<https://www.rfc-editor.org/info/rfc6006>.
9.2. Informative References
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[RFC5862] Yasukawa, S. and A. Farrel, "Path Computation Clients
(PCC) - Path Computation Element (PCE) Requirements for
Point-to-Multipoint MPLS-TE", RFC 5862,
DOI 10.17487/RFC5862, June 2010,
<https://www.rfc-editor.org/info/rfc5862>.
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Authors' Addresses
Huaimo Chen
Futurewei
Boston, MA,
United States of America
Email: Huaimo.chen@futurewei.com
Autumn Liu
Ciena
CA
United States of America
Email: hliu@ciena.com
Mehmet Toy
Verizon
United States of America
Email: mehmet.toy@verizon.com
Vic Liu
Email: liu.cmri@gmail.com
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