Networking Working Group Ran. Chen
Internet-Draft Zheng. Zhang
Intended status: Standards Track ZTE Corporation
Expires: April 15, 2016 October 13, 2015
PCEP Extensions for BIER
draft-chen-pce-bier-00
Abstract
Bit Index Explicit Replication (BIER) is an architecture that
provides optimal multicast forwarding through a "BIER domain" without
requiring intermediate routers to maintain any multicast related per-
flow state. BIER forwards and replicates packets based on a
BitString in the packet header.A BIER Path can be derived from a
variety of mechanisms, including an IGP Shortest Path Tree (SPT),
explicit configuration, or a Path Computation Element (PCE).
This document specifies extensions to the Path Computation Element
Protocol (PCEP) to handle requests and responses for the computation
of paths for BIER TE LSPs.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 15, 2016.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Overview of PCEP Operation in BIER Networks . . . . . . . . . 3
4. BIER PCEP Message Extensions . . . . . . . . . . . . . . . . 3
4.1. BIER Capability Advertisement . . . . . . . . . . . . . . 3
4.1.1. The OPEN Object . . . . . . . . . . . . . . . . . . . 3
4.1.1.1. The BIER PCE Capability TLV . . . . . . . . . . . 3
4.2. Path Computation Request/Reply Message Extensions . . . . 4
4.2.1. The RP/SPR Object . . . . . . . . . . . . . . . . . . 4
4.2.2. The New BIER END-POINT Object . . . . . . . . . . . . 5
4.2.3. ERO Object . . . . . . . . . . . . . . . . . . . . . 5
4.2.3.1. BIER-ERO Subobject . . . . . . . . . . . . . . . 5
4.2.4. RRO Object . . . . . . . . . . . . . . . . . . . . . 7
4.2.4.1. RRO Processing . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6.1. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . 7
6.2. PCEP-Error Objects and Types . . . . . . . . . . . . . . 8
6.3. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 8
6.4. New Path Setup Type . . . . . . . . . . . . . . . . . . . 8
7. Normative references . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Bit Index Explicit Replication (BIER) is an architecture that
provides optimal multicast forwarding through a "BIER domain" without
requiring intermediate routers to maintain any multicast related per-
flow state. BIER forwards and replicates packets based on a
BitString in the packet header.A BIER Path can be derived from a
variety of mechanisms, including an IGP Shortest Path Tree (SPT),
explicit configuration, or a Path Computation Element (PCE).
This document specifies extensions to the Path Computation Element
Protocol (PCEP) to handle requests and responses for the computation
of paths for BIER TE LSPs.
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2. 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.
3. Overview of PCEP Operation in BIER Networks
BIER forwards and replicates packets based on a BitString in the
packet header. In a PCEP session, An ERO object specified in
[RFC5440] carrying a BIER-TE path consists of one or more BIER-
subobject(s). BIER-TE LSPs computed by a PCE can be represented in
one of the following forms:
o An ordered set of BitString(s) in which each bit represents
exactly one router that the BIER-TE paths pass through in the
domain.
o An ordered set of BFR-id(s). In this case, the PCC needs to
convert the BFR-ID into the corresponding BitString(s).
o An ordered set of BFR-prefix(es). In this case, the PCC needs to
convert the BFR-ID into the corresponding B BitString(s).
In this document, we define a set of PCEP protocol extensions,
including a new PCEP capability,a new Path Setup Type (PST) ,a new
BIER END-POINT Object, new ERO subobjects, new RRO subobjects, new
PCEP error codes and procedures.
4. BIER PCEP Message Extensions
The following section describes the protocol extensions required to
support BIER-TE path.
4.1. BIER Capability Advertisement
4.1.1. The OPEN Object
This document defines a new optional TLV for use in the OPEN Object.
4.1.1.1. The BIER PCE Capability TLV
The BIER-PCE-CAPABILITY TLV is an optional TLV associated with the
OPEN Object to exchange BIER capability of PCEP speakers. The format
of the BIER-PCE-CAPABILITY TLV is shown in the following figure:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1
The code point for the TLV type is to be defined by IANA.
The "Reserved" (2 octets) and "Flags" (2 octet) fields are currently
unused, and MUST be set to zero on transmission and ignored on
reception.
4.1.1.1.1. Exchanging BIER Capability
This document defines a new optional BIER-PCE-CAPABILITY TLV for use
in the OPEN object to negotiate the BIER capability. The inclusion
of this TLV in the OPEN message destined to a PCC indicates the PCE's
capability to perform BIER-TE path computations, and the inclusion of
this TLV in the OPEN message destined to a PCE indicates the PCC's
capability to support BIER-TE Path.
A PCE that is able to support the BIER extensions defined in this
document SHOULD include the BIER-PCE-CAPABILITY TLV on the OPEN
message. If the PCE does not include the BIER-PCE-CAPABILITY TLV in
the OPEN message and PCC does include the TLV, it is RECOMMENDED that
the PCC indicates a mismatch of capabilities.
4.2. Path Computation Request/Reply Message Extensions
4.2.1. The RP/SPR Object
In order to setup an BIER-TE LSP, a new PATH-SETUP-TYPE
TLV([I-D.ietf-pce-lsp-setup-type]) MUST be contained in RP or SRP
object. This document defines a new Path Setup Type (PST) for BIER
as follows:
o PST = 2: Path is setup using BIER Traffic Engineering technique.
If a PCEP speaker does not recognize the PATH-SETUP-TYPE TLV, it MUST
ignore the TLV in accordance with [RFC5440]. If a PCEP speaker
recognizes the TLV but does not support the TLV, it MUST send PCErr
with Error-Type = 2 (Capability not supported).
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4.2.2. The New BIER END-POINT Object
The END-POINTS object is used in a PCReq message to specify the BIER
information of the path for which a path computation is requested.
To represent the end points for a BIER path efficiently, we define a
new END-POINT Object for the BIER path:
The format of the new END-POINTS Object 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subdomain-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitStringLength |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2
4.2.3. ERO Object
An BIER-TE path consists of one or more BitString/BFR-id/BFR-prefix
where each BitString/BFR-id/BFR-prefix MAY be associated with the
identifier that represents the node.
The ERO object specified in [RFC5440] is used to carry BIER-TE path
information. In order to carry BitString/BFR-id/BFR-prefix, this
document defines three new ERO subobjects referred to as "BIER-ERO
subobjects" whose formats are specified in the following section. An
ERO object carrying a BIER-TE path consists of one or more BIER-ERO
subobject(s).
4.2.3.1. BIER-ERO Subobject
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD | Length | Flags |BitStringLength|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitStringLength |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3
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=TBD | Length | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4
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=TBD | Length | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BFR-Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5
4.2.3.1.1. ERO Processing
If a PCC finds a non-recognize the SR-ERO subobject, the PCC MUST
respond with a PCErr message with Error-Type=3 ("Unknown Object") and
Error-Value=2 ("Unrecognized object Type") or Error-Type=4 ("Not
supported object") and Error-Value=2 ("Not supported object Type") as
described in [RFC5440] .
If a PCC receives an BIER-ERO subobject format 1 in which either
BitStringLength or BitString is absent, it MUST consider the entire
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ERO object invalid and send a PCErr message with Error-Type = 10
("Reception of an invalid object") and Error-Value = TBD
("BitStringLength is absent ") and Error-Value = TBD ("BitString is
absent ")
If a PCC detects that all subobjects of ERO are not identical, it
MUST send a PCErr message with Error-Type = 10 ("Reception of an
invalid object") and Error-Value = TBD ("Non-identical ERO
subobjects"), as described in ([I-D.ietf-pce-segment-routing])[pce-].
If a PCC receives an SR-ERO subobject in which BFR-ID=0, it MUST send
a PCErr message with Error-Type = 10 ("Reception of an invalid
object") and Error-Value = TBD ("Invalid BFR-ID").
If a PCC receives an SR-ERO subobject in which BitStringLength values
are not chosen from: 64, 128, 256, 512, 1024, 2048, and 4096, as it
described in ([I-D.ietf-bier-architecture]). The PCC MUST send a
PCErr message with Error-Type = 10 ("Reception of an invalid object")
and Error-Value = TBD ("Invalid BitStringLength").
4.2.4. RRO Object
A PCC can record BIER-TE LSP and report the LSP to a PCE via RRO. An
RRO object contains one or more subobjects called "BIER-RRO
subobjects" whose formats are the same as that of SR-ERO subobject.
4.2.4.1. RRO Processing
Processing rules of SR-RRO subobject are identical to those of SR-ERO
subobject defined in section 4.2.3.1.1 in this document.
5. Security Considerations
TBD.
6. IANA Considerations
6.1. PCEP Objects
As discussed in Section 4.2.2, a new END-POINTS Object-Type is
defined. IANA has made the following Object-Type allocations from
the "PCEP Objects" sub-registry:
Object Object-Class Value
--------------------- --------------------------
BIER END-POINT Object TBD
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As discussed in Section 4.2.3 and 4.2.4, a new sub-object type for
the PCEP explicit route object (ERO), and a new sub-object type for
the PCEP record route object (RRO) are defined.
IANA has made the following sub-objects allocation from the RSVP
Parameters registry:
Object Sub-Object Sub-Object Type
--------------------- -------------------------- --------------------------
EXPLICIT_ROUTE BIER-ERO (PCEP-specific) TBD
ROUTE_RECORD BIER-RRO (PCEP-specific) TBD
6.2. PCEP-Error Objects and Types
As described in Section 4.2.3.1.1, a number of new PCEP-ERROR Object
Error Values have been defined.
Error-Type Meaning Reference
---------- ----------------------------------- ---------------------------------
10 Reception of an invalid object. RFC5540
Error-value = TBD: BitStringLength is absent This document
Error-value = TBD: BitString is absent This document
Error-value = TBD: invalid BFR-ID This document
Error-value = TBD: Invalid BitStringLength This document
6.3. PCEP TLV Type Indicators
IANA is requested to allocate a new code point in the PCEP TLV Type
Indicators registry, as follows:
Value Meaning Reference
-------------------- ---------------------------- -----------------------------------
TBD BIER-PCE-CAPABILITY TLV This document
6.4. New Path Setup Type
IANA is requested to allocate a new code point in the PCEP
PATH_SETUP_TYPE TLV PST field registry, as follows:
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Value Description Reference
---------------- ------------------------------------ ----------------------------
2 Path is setup using BIER Traffic This document
Engineering technique
7. Normative references
[I-D.ietf-bier-architecture]
Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
S. Aldrin, "Multicast using Bit Index Explicit
Replication", draft-ietf-bier-architecture-02 (work in
progress), July 2015.
[I-D.ietf-pce-lsp-setup-type]
Sivabalan, S., Medved, J., Minei, I., Crabbe, E., Varga,
R., Tantsura, J., and J. Hardwick, "Conveying path setup
type in PCEP messages", draft-ietf-pce-lsp-setup-type-03
(work in progress), June 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-06 (work in progress), August 2015.
[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>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<http://www.rfc-editor.org/info/rfc5440>.
Authors' Addresses
Ran Chen
ZTE Corporation
No.50 Software Avenue,Yuhuatai District
Nanjing, Jiangsu Province 210012
China
Phone: +86 025 88014636
Email: chen.ran@zte.com.cn
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Zheng Zhang
ZTE Corporation
No.50 Software Avenue,Yuhuatai District
Nanjing, Jiangsu Province 210012
China
Email: zhang.zheng@zte.com.cn
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