PCE Working Group F. Zhang
Internet-Draft Q. Zhao
Intended status: Informational Huawei Technologies
Expires: April 13, 2012 O. Gonzalez de Dios
Telefonica I+D
R. Casellas
CTTC
D. King
Old Dog Consulting
October 13, 2011
Extensions to Path Computation Element Communication Protocol (PCEP) for
Hierarchical Path Computation Elements (PCE)
draft-zhang-pce-hierarchy-extensions-01
Abstract
The hierarchical Path Computation Element (PCE) architecture, defined
in the companion framework document [I-D.ietf-pce-hierarchy-fwk],
allows the selection of an optimum domain sequence and the optimum
end-to-end path, to be derived through the use of a hierarchical
relationship between domains.
This document defines the Path Computation Element Protocol (PCEP)
extensions for the purpose of implementing hierarchical PCE
procedures which are described the aforementioned document.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 13, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. PCEP Extension Requirements . . . . . . . . . . . . . . . . . 4
2.1. Building of parent topology . . . . . . . . . . . . . . . 5
2.2. New Objective Functions . . . . . . . . . . . . . . . . . 5
2.3. PCEP Request Qualifiers . . . . . . . . . . . . . . . . . 6
2.4. Discovery Between Parent and Child PCEs . . . . . . . . . 6
2.4.1. Parent PCE Capability Discovery . . . . . . . . . . . 6
2.4.2. PCE Domain and PCE ID Discovery . . . . . . . . . . . 7
2.5. Domain Connectivity Information Collection . . . . . . . . 7
2.6. Error Case Handling . . . . . . . . . . . . . . . . . . . 8
3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Extensions to OPEN object . . . . . . . . . . . . . . . . 8
3.1.1. OF Codes . . . . . . . . . . . . . . . . . . . . . . . 8
3.1.2. OPEN Object Flags . . . . . . . . . . . . . . . . . . 8
3.1.3. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 9
3.1.4. PCE-ID TLV . . . . . . . . . . . . . . . . . . . . . . 10
3.1.5. Procedures . . . . . . . . . . . . . . . . . . . . . . 10
3.2. Extensions to RP object . . . . . . . . . . . . . . . . . 11
3.2.1. RP Object Flags . . . . . . . . . . . . . . . . . . . 11
3.2.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 11
3.2.3. Procedures . . . . . . . . . . . . . . . . . . . . . . 11
3.3. Extensions to NOTIFICATION object . . . . . . . . . . . . 12
3.3.1. Notification Types . . . . . . . . . . . . . . . . . . 12
3.3.2. Inter-domain Link TLV . . . . . . . . . . . . . . . . 12
3.3.3. Inter-domain Node TLV . . . . . . . . . . . . . . . . 13
3.3.4. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 15
3.3.5. PCE-ID TLV . . . . . . . . . . . . . . . . . . . . . . 15
3.3.6. Procedures . . . . . . . . . . . . . . . . . . . . . . 15
3.4. Extensions to PCEP-ERROR object . . . . . . . . . . . . . 15
3.4.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . . . 15
3.4.2. Procedures . . . . . . . . . . . . . . . . . . . . . . 16
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4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 16
6. Manageability Considerations . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
7.1. Objective Function (OF) codes . . . . . . . . . . . . . . 16
7.2. OPEN Object Flags . . . . . . . . . . . . . . . . . . . . 16
7.3. RP Object Flags . . . . . . . . . . . . . . . . . . . . . 16
7.4. PCEP TLVs . . . . . . . . . . . . . . . . . . . . . . . . 17
7.5. PCEP NOTIFICATION types . . . . . . . . . . . . . . . . . 17
7.6. PCEP PCEP-ERROR types . . . . . . . . . . . . . . . . . . 17
8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
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1. Introduction
[I-D.ietf-pce-hierarchy-fwk] describes a hierarchical PCE
architecture which can be used for computing end-to-end paths for
inter-domain MPLS Traffic Engineering (TE) and GMPLS Label Switched
Paths (LSPs). In the hierarchical PCE architecture, the parent PCE
can compute a multi-domain path based on the domain connectivity
information and each child PCE is able to compute the intra-domain
path based on its domain topology information. The end-to-end domain
path computing procedures can be abstracted as follows:
o A path computation client (PCC) requests its own child PCE the
computation of an inter-domain path.
o The child PCE forwards the request to the parent PCE.
o The parent PCE computes one or multiple domain paths from the
ingress domain to the egress domain.
o The parent PCE sends the intra-domain path computation requests
(between the domain border nodes) to the child PCEs which are
responsible for the domains along the domain path(s).
o The child PCEs return the intra-domain paths to the parent PCE.
o The parent PCE constructs the end-to-end inter-domain path based
on the intra-domain paths and returns the inter-domain path to the
child PCE.
o The child PCE forwards the inter-domain path to the PCC.
This document defines the PCEP extensions for the purpose of
implementing hierarchical PCE procedures, which are described in
[I-D.ietf-pce-hierarchy-fwk].
The document also uses a number of editor notes to describe options
and alternative solutions. These options and notes will be removed
before publication.
1.1. Terminology
This document uses the terminology defined in [RFC4655], [RFC5440]
and [I-D.ietf-pce-hierarchy-fwk].
1.2. 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. PCEP Extension Requirements
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2.1. Building of parent topology
As stated in section 5.4 of [I-D.ietf-pce-hierarchy-fwk] a parent PCE
maintains a domain topology map and may contain nodes and links on
its own right, maintaining a traffic engineering database (TED) for
the parent domain.
The parent PCE TED may be configured or learnt by the child PCEs.
Editors note. A child PCE could forward the topology within PCNtf
messages or any other mechanisms, without an IGP adjacency. Further
discussion of the discovery mechanism and scope will be discussed in
later versions of this document.
2.2. New Objective Functions
For inter-domain path computation, there are three new objective
functions which are defined in section 1.3.1 of
[I-D.ietf-pce-hierarchy-fwk].
o Minimize the number of boundary nodes used.
o Limit the number of domains crossed.
o Disallow domain re-entry.
During the PCEP session establishment procedure, the parent PCE needs
to be capable of indicating the objective functions (OF) capability
in the Open message. This information can be, in turn, announced by
child PCEs and used for selecting the PCE when a PCC want a path that
satisfies a certain inter-domain objective function.
When a PCC requests a PCE to compute an inter-domain path, the PCC
needs also to be capable of indicating the new objective functions
for inter-domain path. Note that a given PCE may act as a regular
PCE and as a parent PCE.
For the reasons described above, new OF codes need to be defined for
the new inter-domain objective functions. Then the PCE can notify
its new inter-domain objective functions to the PCC by carrying them
in the OF-list TLV which is carried in the OPEN object. The PCC can
specify which objective function code to use, which is carried in the
OF object when requesting a PCE to compute an inter-domain path.
The proposed solutions may need to differentiate between the OF code
that is requested at the parent level and the OF code that is
requested at the intra-domain (child) level.
A parent PCE needs to be able to insure homogeneity when applying OF
codes for the intra-domain requests.
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2.3. PCEP Request Qualifiers
As described in section 5.8.1 of [I-D.ietf-pce-hierarchy-fwk], the
H-PCE architecture will introduce new request qualifications as
follows:
o It MUST be possible for a child PCE to indicate that a request it
sends to a parent PCE should be satisfied by a domain sequence
only, that is, not by a full end-to-end path. This allows the
child PCE to initiate a per-domain [RFC5152] or a backward
recursive path computation (BRPC) [RFC5441].
o A parent PCE needs to be able to ask a child PCE whether a
particular node address (the destination of an end-to-end path) is
present in the domain that the child PCE serves.
o As stated in [I-D.ietf-pce-hierarchy-fwk], section 5.5, if a PCC
knows the egress domain, it can suppy this information as the path
computation request. It SHOULD be possible to specify the
destination domain information in a PCEP request, if it is known.
To meet the above requirements, the PCEP PCReq message should be
extended.
2.4. Discovery Between Parent and Child PCEs
In the H-PCE architecture, the parent PCE does not need to be aware
of each child domain topology. Therefore, it is possible that the
parent PCE does not join the IGP instance of the child PCE domain,
i.e. there is no IGP discovery mechanism between the parent PCE and
child PCE.
Therefore there must be a discovery mechanism for basic PCE
information between the parent and child PCEs. In this case, PCEP
needs to provide discovery mechanisms that do not rely on IGP
announcement/discovery procedures. A simple discovery mechanism
relies on the static configuration / provisioning of the parent PCE
id and address, which is configured at each child PCE.
2.4.1. Parent PCE Capability Discovery
As described in [I-D.ietf-pce-hierarchy-fwk], during the PCEP session
establishment procedure, the child PCE needs to be capable of
indicating to the parent PCE whether it requests the parent PCE
capability or not. The parent PCE needs also to be capable of
indicating whether its parent capability can be provided to the child
PCE or not.
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2.4.2. PCE Domain and PCE ID Discovery
A PCE domain is a single domain with an associated PCE. it is
possible for a PCE to manage multiple domains. The PCE domain may be
an IGP area or AS.
The PCE ID is an IPv4 and/or IPv6 address that is used to reach the
parent/child PCE. It is RECOMMENDED to use an address that is always
reachable if there is any connectivity to the PCE.
The PCE ID information and PCE domain identifiers may be provided
during the PCEP session establishment procedure or the domain
connectivity information collection procedure.
2.5. Domain Connectivity Information Collection
As described in [I-D.ietf-pce-hierarchy-fwk], the parent PCE builds
the domain topology map either from configuration or from information
received from each child PCE. A child PCE may report its neighbor
domain connectivity to its parent PCE. It is reasonable to use PCEP
PCNtf message to do this procedure. If an IGP adjacency is
established between parent and children, it could be used for this
purpose.
There are two types of domain border for providing the domain
connectivity information:
o Domain border is a TE link, e.g. the inter-AS TE link which
connects two ASs.
o Domain border is a node, e.g. the IGP ABR which connects two IGP
areas.
For the inter-AS TE links, the following information needs to be
notified to the parent PCE:
o Identifier of advertising child PCE.
o Identifier of PCE's domain.
o Identifier of the link.
o TE properties of the link (metrics, bandwidth).
o Other properties of the link (technology-specific).
o Identifier of link end-points.
o Identifier of adjacent domain.
For the ABR, the following information needs to be notified to the
parent PCE:
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o Identifier of the ABR.
o Identifier of the IGP Area IDs.
2.6. Error Case Handling
A PCE that is capable of acting as a parent PCE might not be
configured or willing to act as the parent for a specific child PCE.
This fact could be determined when the child sends a PCReq that
requires parental activity (such as querying other child PCEs), and
could result in a negative response in a PCEP Error (PCErr) message
and indicate the hierarchy PCE error types.
3. PCEP Extensions
3.1. Extensions to OPEN object
3.1.1. OF Codes
There are three new OF codes defined here for H-PCE:
o MBN
* Name: Minimize the number of Boundary Nodes used
* Objective Function Code: (to be assigned by IANA, recommended
11)
* Description: Find a path P such that passes through the least
boundary nodes.
o MTD
* Name: Minimize the number of Transit Domains
* Objective Function Code: (to be assigned by IANA, recommended
12)
* Description: Find a path P such that passes through the least
transit domains.
o DDR
* Name: Disallow Domain Re-entry (DDR)
* Objective Function Code: (to be assigned by IANA, recommended
13)
* Description: Find a path P such that does not entry a domain
more than once.
3.1.2. OPEN Object Flags
There are two OPEN object flags defined here for H-PCE:
o Parent PCE request bit (to be assigned by IANA, recommended bit
0): if set it means the child PCE wishes to use the peer PCE as a
parent PCE.
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o Parent PCE indication bit (to be assigned by IANA, recommended bit
1): if set it means the PCE can be used as a parent PCE by the
peer PCE.
o Editors Note. It is possible that a parent PCE will also act as a
child PCE.
3.1.3. Domain-ID TLV
The type of Domain-ID TLV is to be assigned by IANA (recommended 7).
The length is 8 octets. The format of this TLV is defined below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Domain-ID TLV
Domain Type (8 bits): Indicates the domain type. There are two types
of domain defined currently:
o Type=1: the Domain ID field carries an IGP Area ID.
o Type=2: the Domain ID field carries an AS number.
Domain ID (32 bits): Indicates an IGP Area ID or AS number.
An AS number may be 2 or 4 bytes long. For 2-byte AS numbers, the AS
value is left-padded with 0.
Editor's note: it may be necessary to support 64 bit domain IDs.
Editor's note: draft-dhody-pce-pcep-domain-sequence, section 3.2
deals with the encoding of domain sequences, using ERO-subobjects.
Work is ongoing to define domain identifiers for OSPF-TE areas, IS-IS
area (which are variable sized), 2-byte and 4-byte AS number, and any
other domain that may be defined in the future. It uses RSVP-TE
subobject discriminators, rather than new type 1/ type 2. A domain
sequence may be encoded as a route object. The "VALUE" part of the
TLV could follow common RSVP-TE subobject format:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Type | Length | AS Id (2 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Alternative Domain-ID TLV
3.1.4. PCE-ID TLV
The type of PCE-ID TLV is to be assigned by IANA (recommended 8).
The length is 8. The format of this TLV is defined below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// PCE IP Address //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: PCE-ID TLV
Address Type (16 bits): Indicates the address type of PCE IP Address.
1 means IPv4 address type, 2 means IPv6 address type.
PCE IP Address: Indicates the reachable address of a PCE.
Editor's note: RFC5886 already defines the PCE-ID object. If a
semantically equivalent PCE-ID TLV is needed (to avoid modifying
message grammars to include the object), it can align with the PCEP
object: n any case, the length (4 / 16 bytes) can be used to know
whether it is an IPv4 or an IPv6 PCE, the address type is not needed.
3.1.5. Procedures
The OF codes defined in this document can be carried in the OF-list
TLV of the OPEN object. If the OF-list TLV carries the OF codes, it
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means that the PCE is capable of implementing the corresponding
objective functions. This information can be used for selecting a
proper parent PCE when a child PCE wants to get a path that satisfies
a certain objective function.
If a child PCE wants to use the peer PCE as a parent, it can set the
parent PCE request bit in the OPEN object carried in the Open message
during the PCEP session creation procedure. If the peer PCE does not
want to provide the parent function to the child PCE, it must send a
PCErr message to the child PCE and clear the parent PCE indication
bit in the OPEN object.
If the parent PCE can provide the parent function to the peer PCE, it
may set the parent PCE indication bit in the OPEN object carried in
the Open message during the PCEP session creation procedure.
The PCE may also report its PCE ID and list of domain ID to the peer
PCE by specifying them in the PCE-ID TLV and List of Domain-ID TLVs
in the OPEN object carried in the Open message during the PCEP
session creation procedure.
3.2. Extensions to RP object
3.2.1. RP Object Flags
o Domain Path Request bit (to be assigned by IANA, recommended bit
17): if set it means the child PCE wishes to get the domain
sequence.
o Destination Domain Query bit (to be assigned by IANA, recommended
bit 16): if set it means the parent PCE wishes to get the
destination domain ID.
3.2.2. Domain-ID TLV
The format of this TLV is defined in section Section 3.1.3. This TLV
can be carried in an OPEN object to indicate a (list of) managed
domains, or carried in a RP object to indicate the destination domain
ID when a child PCE responds to the parent PCE's destination domain
query by a PCRep message.
Editors note. In some cases, the Parent PCE may need to allocate a
node which is not necessarily the destination node.
3.2.3. Procedures
If a child PCE only wants to get the domain sequence for a multi-
domain path computation from a parent PCE, it can set the Domain Path
Request bit in the RP object carried in a PCReq message. The parent
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PCE which receives the PCReq message tries to compute a domain
sequence for it. If the domain path computation succeeds the parent
PCE sends a PCRep message which carries the domain sequence in the
ERO to the child PCE . The domain sequence is specified as AS or
AREA ERO sub-objects (type 32 for AS [RFC3209] or a to-be-defined IGP
arrea type). Otherwise it sends a PCReq message which carries the
NO-PATH object to the child PCE.
The parent PCE can set the Destination Domain Query bit in a PCReq
message to query the destination (which is specified in the END-
POINTS objects) domain ID from a child PCE. If the child PCE knows
the destination(s) domain ID, it sends a PCRep message to the parent
PCE and specifies the domain ID in the Domain-ID TLV which is carried
in the RP object. Otherwise it sends a PCRep message with a NO-PATH
object to the parent PCE.
3.3. Extensions to NOTIFICATION object
Because there will not be too many PCEP sessions between the child
PCE(s) and parent PCE, it is recommended that the PCEP sessions
between them keeping alive all the time . Then the child PCE can
report all of the domain connectivity information to the parent PCE
when the PCEP session is established successfully. It can also
notify the parent PCE to update or delete the domain connectivity
information when it detects the changes.
3.3.1. Notification Types
There is a new notification type defined in this document:
o Domain Connectivity Information notification-type (to be assigned
by IANA, recommended 3).
* Notification-value=0: sent from the parent to the child to
query all of the domain connectivity information maintained by
the child PCE.
* Notification-value=1: sent from the child to the parent to
update the domain connectivity information maintained by the
child PCE.
* Notification-value=2: sent from the child to the parent to
delete the domain connectivity information maintained by the
child PCE.
3.3.2. Inter-domain Link TLV
IGP in each neighbor domain can advertise its inter-domain TE link
capabilities [RFC5316], [RFC5392]. This information can be collected
by the child PCEs and forwarded to the parent PCE. PCEP Inter-domain
Link TLV is used for carrying the inter-domain TE link attributes for
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this purpose. Each Inter-domain Link TLV can carry the attributes of
one inter-domain link at the most.
The type of Inter-domain Link TLV is to be assigned by IANA
(recommended 9). The length is variable. The format of this TLV is
defined below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertise Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// sub-TLVS //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Inter-domain Link TLV
Editor's note: evaluate other possibilities regarding the wrapping
and encoding (LSAs / LSUs). Other fields may be needed, such as LSA
age (max age methods can be used to "withdraw" or remove a link).
Sub-TLVs may need to be defined in the context of a Link TLV (top
TLV).
Advertise Router ID (32 bits): indicates the router ID which
advertises the TE LSA or LSP.
Sub-TLVs: the OSPF sub-TLVs for a TE link which defined in [RFC5392]
and other associated OSPF RFCs. It is noted that if the IGP is IS-IS
for the child domain the sub-TLVs must be converted to the OSPF sub-
TLVs format when sending this information to the parent PCE through
PCEP PCNtf message.
Each inter-domain link is identified by the combination of advertise
router ID and the link local IP address or link local unnumbered
identifier. The PCNtf message which is used for notifying the parent
PCE to update or delete a inter-domain link must contain the
information identifies a TE link exclusively.
3.3.3. Inter-domain Node TLV
The Inter-domain Node TLV carries only the two adjacent domain ID and
the router (IGP ABR) ID.
The type of Inter-domain Node Information TLV is to be assigned by
IANA (recommended 10). The length is variable . The format of this
TLV is defined 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ABR ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Area ID1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Area ID2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Inter-domain Node TLV
ABR ID (32 bits): indicates the domain border router ID.
Area ID1 & Area ID2 (32 bits): indicates the two neighbor area IDs.
Editor's note (1): a node may be an inter-domain node for more than
just 2 areas, the encoding is wrong, unless we explicitly state that
this TLV can be repeated and we give an example. Alternatively, we
can use the generic concept of "domain id" as introduced earlier, to
avoid the restriction of 4 byte areas only.
Editor's note (2): do we homogenize so we also have a Advertising
Router ID? would it be different from the ABR id?
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertise Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ABR ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IS/IS area 1 ... |
.. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IS/IS area 2 ... |
.. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Alternative Inter-domain Node TLV
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3.3.4. Domain-ID TLV
The format of this TLV is defined in section Section 3.1.3. This TLV
can be carried in a NOTIFICATION object to indicate the domain ID of
the PCE who sends the PCNtf message.
Editors note. A PCE may be responsible for several domains, it may
be beneficial to use a list of TLVs.
3.3.5. PCE-ID TLV
The format of this TLV is defined in section Section 3.1.4. This TLV
can be carried in a NOTIFICATION object to indicate the PCE ID of the
PCE who sends the PCNtf message.
3.3.6. Procedures
When a parent PCE establishes a PCEP session with a child PCE
successfully, the parent PCE may request the child PCE to report the
domain connectivity information. This procedure can be done by
sending a PCNtf message from the parent to the child, setting the
notification-type to 3 and notification-value to 0 in the
NOTIFICATION object.
When a child PCE receives the PCNtf message, it may send all of the
domain connectivity information to the parent PCE by the PCNtf
message(s). The notification-type is 3 and notification-value is 1
in the NOTIFICATION object. The NOTIFICATION object may carry the
inter-domain link TLV and inter-domain node TLV to describe the
inter-domain connectivity information. It is noted that if the child
PCE dose not support this function, it will ignore the received PCNtf
message and the parent PCE will not receive the response.
The child PCE can also update the domain connectivity information by
re-sending the PCNtf message(s) with the newly information.
When the child PCE detects a deletion of domain connectivity (e.g.,
the inter-domain link TLV is aged out), it must notify the parent PCE
to delete the inter-domain link by sending the PCNtf message. The
notification-type is 3 and notification-value is 2 in the
NOTIFICATION object.
3.4. Extensions to PCEP-ERROR object
3.4.1. Hierarchy PCE Error-Type
A new PCEP Error-Type is allocated for hierarchy PCE (to be assigned
by IANA, recommended 19):
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+------------+------------------------------------------------------+
| Error-Type | Meaning |
+------------+------------------------------------------------------+
| 19 | H-PCE error Error-value=1: parent PCE capability |
| | cannot be provided |
+------------+------------------------------------------------------+
Table 1: H-PCE error table
3.4.2. Procedures
When a specific child PCE sends a PCReq to a peer PCE that requires
parental activity and the peer PCE does not want to act as the parent
for it, the peer PCE should send a PCErr message to the child PCE and
specify the error-type (IANA) and error-value (1) in the PCEP-ERROR
object.
4. Acknowledgements
5. Contributors
TBD.
6. Manageability Considerations
TBD.
7. IANA Considerations
As per RFC 5226 [RFC5226], IANA is requested to create/update the
following registries
7.1. Objective Function (OF) codes
Value Meaning Reference
11 MBN This document
12 MTD This document
13 DDR This document
7.2. OPEN Object Flags
7.3. RP Object Flags
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7.4. PCEP TLVs
Value Meaning Reference
x Interdomain Link TLV This document (section Section 3.3.2)
x Interdomain Node TLV This document (section Section 3.3.3)
7.5. PCEP NOTIFICATION types
Type Value Meaning
P2C Notification 1
2
3
C2P Notification 1
2
3
7.6. PCEP PCEP-ERROR types
Type Value Meaning
H-PCE Error 19 1 parent PCE capability cannot be provided
2 TBD
3 TBD
8. Security Considerations
TBD.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5152] Vasseur, JP., Ayyangar, A., and R. Zhang, "A Per-Domain
Path Computation Method for Establishing Inter-Domain
Traffic Engineering (TE) Label Switched Paths (LSPs)",
RFC 5152, February 2008.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440,
March 2009.
[RFC5441] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A
Backward-Recursive PCE-Based Computation (BRPC) Procedure
to Compute Shortest Constrained Inter-Domain Traffic
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Engineering Label Switched Paths", RFC 5441, April 2009.
9.2. Informative References
[I-D.ietf-pce-hierarchy-fwk]
King, D. and A. Farrel, "The Application of the Path
Computation Element Architecture to the Determination of a
Sequence of Domains in MPLS and GMPLS",
draft-ietf-pce-hierarchy-fwk-00 (work in progress),
October 2011.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
Support of Inter-Autonomous System (AS) MPLS and GMPLS
Traffic Engineering", RFC 5316, December 2008.
[RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in
Support of Inter-Autonomous System (AS) MPLS and GMPLS
Traffic Engineering", RFC 5392, January 2009.
Authors' Addresses
Fatai Zhang
Huawei Technologies
F3-5-B R&D Center, Huawei Base. Bantian, Longgang District
Shenzhen, 518129
P.R.China
Phone: +86-755-28972912
Email: zhangfatai@huawei.com
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Quintin Zhao
Huawei Technologies
125 Nagog Technology Park
Acton, MA 01719
US
Phone:
Email: qzhao@huawei.com
Oscar Gonzalez de Dios
Telefonica I+D
Emilio Vargas, 6
Madrid,
Spain
Phone:
Email: ogondio@tid.es
Ramon Casellas
CTTC
Av. Carl Friedrich Gauss n.7
Castelldefels, Barcelona
Spain
Phone: +34 93 645 29 00
Email: ramon.casellas@cttc.es
Daniel King
Old Dog Consulting
Phone:
Email: daniel@olddog.co.uk
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