Network Working Group D. Wang
Internet-Draft Z. Wang
Intended status: Informational Q. Xiang
Expires: May 1, 2009 F. Gao
ZTE Corporation
October 28, 2008
PCECP Requirements and Extensions of Alternate Routing for Wavelength
Switched Optical Networks
draft-wang-pce-wson-alternate-routing-00.txt
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Abstract
This memo provides application-specific requirements and extensions
of alternate routing for the support of Wavelength Switched Optical
Networks (WSON).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. PCECP Extended Requirements for AR . . . . . . . . . . . . . . 5
5.1. AR Computation Policy . . . . . . . . . . . . . . . . . . 5
5.2. Extended PCE Request Information for AR . . . . . . . . . 6
5.2.1. Loose Constraints Inquiry . . . . . . . . . . . . . . 7
5.2.2. Constraint Routing Inquiry Strategy . . . . . . . . . 7
5.2.3. Sequence Strategy of Alternate Routes . . . . . . . . 8
5.2.4. Maximum Complexity of Time and Space about AR
Computation . . . . . . . . . . . . . . . . . . . . . 9
5.3. Response of Alternate Routes From PCEs . . . . . . . . . . 9
5.3.1. Basic Information of Alternate Routes . . . . . . . . 9
5.3.2. Form of Alternate Routes . . . . . . . . . . . . . . . 10
5.3.3. Content of Each hop in Alternate Routes . . . . . . . 10
5.4. AR Computation Strategy with Inclusion Constraints . . . . 11
5.5. The Relationship between Primary Route and Backup
Route in AR . . . . . . . . . . . . . . . . . . . . . . . 11
5.6. Re-routing of Optimization under AR . . . . . . . . . . . 12
5.7. Re-routing of Fault Recovery under AR . . . . . . . . . . 12
5.8. Hierachical Routing in AR Computation . . . . . . . . . . 12
6. PCECP Extended Requirements for AR . . . . . . . . . . . . . . 13
6.1. Subobject of AR Extended Constraints . . . . . . . . . . . 13
6.2. Requset of Alternate Routes . . . . . . . . . . . . . . . 16
6.3. Response of Alternate Routes . . . . . . . . . . . . . . . 17
6.3.1. Basic Information Object . . . . . . . . . . . . . . . 17
6.3.2. Alternate Routes Subobjects . . . . . . . . . . . . . 18
7. Manageability Considerations . . . . . . . . . . . . . . . . . 20
7.1. Control of Function and Policy . . . . . . . . . . . . . . 20
7.2. Information and Data Models . . . . . . . . . . . . . . . 21
7.3. Liveness Detection and Monitoring . . . . . . . . . . . . 21
7.4. Verifying Correct Operation . . . . . . . . . . . . . . . 21
7.5. Requirements on Other Protocols and Functional
Components . . . . . . . . . . . . . . . . . . . . . . . . 21
7.6. Impact on Network Operation . . . . . . . . . . . . . . . 21
8. Security Considerations . . . . . . . . . . . . . . . . . . . 21
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
11.1. Normative References . . . . . . . . . . . . . . . . . . . 22
11.2. Informative References . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
Intellectual Property and Copyright Statements . . . . . . . . . . 25
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1. Introduction
[RFC4655] respectively defines PCE Architectures and describes the
routing generating mechanism when a PCC originates a LSP's routing
request. In Wavelength Switched Optical Networks (WSON), PCE is a
key way to provide routes for services. At the same time, some PCEs
can also have a function of realizing Wavelength Assignment(WA). As
a common sense, Routing and Wavelength Assignment (RWA) is the first
problem that WSON has to face. Meanwhile, RWA is truly a
Nondeterministic Polynominal-Complete(NP-C) problem. Whatever RWA
computation architectures (such as Combined RWA, Separate Routing and
WA, Routing with Distributed WA, etc) are all confronted with two
inevitable and divided procedures: route calculation, wavelength
assignment. In many cases, LSP signalling can not be normally runned
by the Label Switching Routers(LSRs) in the given route that some PCE
supplies,especially in typical WSON. It is mainly resulted from WA
failing in the LSRs that the service connection passes. WA blocking
becomes the direct reason. (About why WA blocking occurs, please
refer to other related drafts.) So Alternate Routing(AR) is proposed
for the problem of WA failings in WSON. Alternate paths have
appeared in RFC4655. AR means the routing of a service request over
a substitute route when a primary route is unavailable for immediate
use. When head-end node fails to establish the service according to
the first provided route by some PCE, it can choose other routes and
go on analysis of WA along the selected route.
The PCE Communication Protocol (PCECP) is the communication protocol
used between a PCC and a PCE, and may also be used between
cooperating PCEs. [RFC4657] sets out the common protocol
requirements for PCECP. Additional application-specific requirements
for PCECP are deferred to separate documents. This document provides
a set of application-specific PCECP requirements and protocol
enhancements for support of AR in WSON.
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 RFC-2119.
3. Background
The WSON framework [WSON-FRAME] document defines the following RWA
computation architectures.
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o Combined RWA (CRWA) --- Both R and WA are performed at a single
computational entity. This choice assumes that computational
entity has sufficient WSON network link/node and topology
information to be able to compute RWA.
o Separate Routing and WA (SRWA) --- Separate entities perform R and
WA. The path(s) obtained from the routing computational entity
must be furnished to the entity performing WA.
o Routing with Distributed WA (RDWA) --- R is performed at a
computational entity while WA is performed in a distributed
fashion across the nodes along the path.
For the CRWA architecture, there are two possible computing entities:
(i) the NE is the computational entity -- in this case, there is no
separate PCE as the NE assumes PCE function; (ii) a separate PCE is
the computational entity.
For the SRWA architecture, there can be two variations:
o A separate PCE will perform only WA while the NE performs the
route calculation based on its local knowledge. In this case, the
NE should furnish the route list to the PCE so that the PCE would
be able to assign wavelength to the route.
o One PCE performs the R function while another PCE performs the WA
function in a tandem fashion. The fact that two PCEs are involved
(one for R and the other for WA) could be invisible to the
original PCC.
For the RDWA architecture, the PCE is only responsible for R(i.e.,
path computation), not for exact WA. The exact assignment of
wavelengths would be performed at the NEs along the path in a
distributed fashion. However, the PCE may limit the wavelengths that
can be used (i.e., by specifying a wavelength set to the NEs).
4. Terminology
AR: Alternate Routing.
AS: Autonomous System.
CP: Control Plane.
CRWA: Combined RWA.
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CSPF: Constraint-based Shortest Path First.
NE: Network Element.
NMS: Network Mangagement System.
ODU: Optical Channel Data Unit.
ODUk: Optical Channel Data Unit-k.
OSC: Optical Supervisory Channel.
PCC: Path Computation Client.
PCE: Path Computation Element.
PCECP: PCE Communication Protocol.
R: Routing.
RDWA: R with Distributed WA.
ROADM: Reconfigurable Optical Add/Drop Multiplexer.
RWA: Route and Wavelength Assignment.
SRWA: Separate RWA.
TE: Traffic Engineering.
WA: Wavelength Assignment.
WDM: Wavelength Division Multiplexing. WSON: Wavelenght Switch
Optical Network.
5. PCECP Extended Requirements for AR
5.1. AR Computation Policy
The AR computation policy represents a set of rules which defines the
relation between PCEs and the PCCs in term of route exchanges and
protocol interaction.
To summarize, the AR computation policy can be defined as the
following two types:
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o All the routes of one topology will be computated by PCEs in
advance. In this case, routes computation will not depend on
PCCs' requests. Periodically PCEs complete all routes computation
of the topology which they know and save them in local caches. At
the same time, once the known topology is changed(such as opaque
lsas are aged, updated, added, etc.), routes computation also
occur in the PCEs. And especially in CRWA's scenario, WA also can
be previously solved in each route before PCCs' requests. In this
way, when a PCC's request comes, the PCE can search the suitable
route matched with the request's constraints among the saved
routes. So it is good for the PCC that it does not takes the PCC
time to wait for computating the route. But the method of
preprocessing routing has defects, too. If all of saving routes
does not meet the PCC's constraints, RWA process will fail. So it
is fitter for the route inquiry with loose constraints.
By the way, in "multiple PCE path computation" case(see [RFC4655]
), at least one of the PCEs must have the function of assembling
partitional routes into a complete route ahead of time.
o A real-time route computation will be executed by PCEs according
to one PCC's request. In this case, route computation will not
occur until the PCE receives a request from some PCC. Then the
PCE will begin to compute the route according to the PCC's request
including some constraints and the PCC has to wait for the PCE's
computation. So the time of route computation will be added to
the PCE's reponse delay time. In addition, the complexity of
algorithm that the PCE uses will be considered.
5.2. Extended PCE Request Information for AR
In [RFC4655] 5.1.16., [draft-ietf-pce-pcep-xro-06], and [draft-ietf-
pce-pcep-16], constraints and request information have also been
raised. On the basis of the list of generic information, extended
information SHOULD be added in need of the AR case.
The set of supported extended information SHOULD include at least the
following:
o The route direction. Used to indicate whether the alternate
routes should satisfy the specified constraints in both forward
and reverse directions.
It includes two options:
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- Unidirection.
- Bidirection.
o Upper limit of K. Used to limit the maximum number of alternate
routes computed by the PCE.
o Constraint routing inquiry strategy.
o Sequence Strategy of Alternate Routes.
o Maximum complexity of time and space about AR computation.
5.2.1. Loose Constraints Inquiry
Commonly constraints are thinked as strict constraints. It means
that AR computation MUST satisfy the constraints, else the PCE will
repond AR computation failure. Here, loose constraint is introduced.
If computed alternate routes just need meet at least one of the loose
constraints, the PCE will respond them to the PCC successfully.
Otherwise if no loose constraint can be met, the PCE will return a
failing response. The loose constraints also contain Link, Node,
Shared Risk Link Group (SRLG) inclusion/exclusion. Furthermore,
these constraints can be combined and be arranged in priority. For
the loose, the higher priority of the constraint is, the earlier the
constraint will be met.
The loose constraints are listed in descending order of priority:
o Nodes includsion.
o Links includsion.
o SRLGs includsion.
o Nodes excludsion.
o Links excludsion.
o SRLGs excludsion.
o And the PCC can also combined the above constraints.
5.2.2. Constraint Routing Inquiry Strategy
In [RFC4657] and [RFC3209], both strict routes and loose routes are
mentioned. Just as RFC4657 has mentioned, routes constraints usually
include Link, Node, Shared Risk Link Group (SRLG) inclusion/
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exclusion, etc. Now as a consrtaint inquiry prefercence, here we
introduce the conception of constraint routing inquiry strategy and
give the constructive definition of it.
It includes four types:
- Strict constraints inquiry only. AR computation MUST satisfy the
constraints including all of the above-mentioned constraints.
- Loose constraints inquiry only. At this moment, AR computation
just need meet at least one of the above-mentioned constraints.
If no constraint can be met, the PCE will return a failing
response to the PCC.
- Coexistence of them. Sometimes, Both Strict inquiry and loose
inquiry are requested at the same time. Then PCEs should process
them respectivly according to the former different ways.
- Neither of them. Routing inquiry is performed without any
constraints.
5.2.3. Sequence Strategy of Alternate Routes
When the PCC asks alternate routes for PCEs, it is preferable to
offer the alternate routes in a designated sequence. In that case,
the PCC need to supply a sequence strategy in its request. In
[RFC4657], the objective functions of unsynchronized and synchronized
path computations are introduced to us. Based on them, till now,
there are some sequence strategies summarized in WSON as following:
- 00 Minimum aggregate te-metrics. It is the familiarest sequence
type that is equal to CSPF strategy.
- 01 Minimum hops number. In fact, this type is deduced from the
above. We can look it as that the te-meteric of every hop that
every path includes is one. Then if the hypothesis is formed,
that will be the above type.
- 02 Maximum disjoint nodes as possible. Sometimes, for the PCC's
need, the alternate routes are sequenced under the consideration
of nodes that routes inlcude being parted each other as possible.
Supposing that when the PCC receives the PCE's successful response
(Here, we consider the RDWA scenario .), it will use the first
provided route to perform WA. Once WA fails in the used path,
then another alternate route will be selected. It is more likely
that WA succeeds using the path consisting of ultimately different
nodes. So important this strategy is, and the next two strategies
are homothetic.
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- 03 Maximum disjoint links as possible.
- 04 Maximum disjoint SRLGs as possible.
- 05 Highest efficient use based on bandwidth granularity. In WSON,
RWA processes of the sevices which in batch processing are
initiated by the NMS will be computed at a variety of bandwidth
granularities. Generally speaking, there are k kinds of bandwidth
granularities according to ODUk supported by the transport plane.
At this time, alternate routes computed by the PCE will be
sequenced in the residual bandwidth of the links that the every
alternate route contains and the bandwidth granularity that the
sevice to be set up needs. For example, now there are three
alternate routes for a service connection of which bandwidth
granularity is ODU0. And the residual bandwidth granularities in
their contained links are ODU1 ODU2, and ODU0 respectively. In
this strategy, we can arrange such routes in the granularity
order: ODU0, ODU1, ODU2. So in this method, we can avoid the
fragment of free bandwidth appearing as possible.
- 06 Highest load balancing degree. Load balancing problem has been
cared for in AR. To some extent, it is similar to "maximize the
residual bandwidth on the most loaded link" in RFC4657. Here, it
is also used for the loaded SRLG.
5.2.4. Maximum Complexity of Time and Space about AR Computation
In RFC4655 "6.4. PCE Discovery and load balancing, The PCC may learn
PCE capabilities through static configuration, or it may discover the
information dynamically." Besides the PCE capabilities described in
RFC4655, by maximum complexity of time and space about AR
computation, the PCC can estimate the PCE's capabilities. Once the
time or the space for the PCC's AR computation exceeds this
constraint, the PCE will respond AR computation failure and the PCC
will select another appropriate PCE for its purposes under the
control of policy.
5.3. Response of Alternate Routes From PCEs
In the case of AR in WSON, the PCE should return the K alternate
routes to the PCC.
5.3.1. Basic Information of Alternate Routes
Basic information of alternate routes should include:
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- the actual number of alternate routes that the PCE computes.
- the algorithm's complexity of time and space. By this
information, the PCC can learn the capability and efficiency of
PCE, so that it can adjust the strategy and choose the suitable
PCE in time.
- the range of which the PCE is responsible for AR computation. It
should include the areas' IDs, the sub areas' IDs that the PCE
deals with.
5.3.2. Form of Alternate Routes
The K alternate routes can be described in a serial format.
Different routes can be distinguished by the head-end node's hop.
And when the PCC receives the packets, it can extract every route by
judging the head-end hops which contain the head and the end nodes'
IDs.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| basic information of alternate routes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| the 1st route | head hop | hop1 | hop2' |.....| end hop |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| the 2nd route | head hop' | hop1' | hop2' |.....| end hop' |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| the kth route | head hop''| hop1''| hop2''|.....| end hop'' |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.3.3. Content of Each hop in Alternate Routes
In RFC4657 "5.1.5.Path Computation Responses", the information which
is responded by the PCE has been cared for. But it does not be
described in detail and does not be extended. Especially in WSON,
each hop of each alternate route should contain R and WA information.
It MUST providing the following mandatory R information:
- Node ID.
- IP address of each hop's output interface.
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- Metric of each hop.
- Residual bandwidth of each hop.
It MAY providing the following optional WA information :
- Free wavelength set of each hop. It can be used for RDWA when WA
process has not been executed.
- Definite used wavelength of each hop by WA analysis. It can be
used for CRWA when the PCE has the funciton of WA at the same
time.
5.4. AR Computation Strategy with Inclusion Constraints
It is well-known that inclusion constrains, such as nodes, links,
SRLGs, and the combined separate the route from head to end nodes
into several segments. In this case, AR computation will be
performed in segment by at least one PCE . If the numbers of
alternate sub-routes of segments are k1, k2, k3,....kn respectivly.
Thus the number of full routes by assembling is at most
k1*k2*k3....*kn considering perhaps there are repeated nodes, links
and SRLGs among the sub-routes. The function of assembling sub-
routes can be executed by a designated PCE. At last, the PCE will
respond the full alternate routes to the PCC or go on to perform the
WA analysis by them. and pay attention to isolate nodes appear.
5.5. The Relationship between Primary Route and Backup Route in AR
For the purpose of Automatic Protection Switching (APS), the PCE can
provide two kinds of routes, one is the primary route for the work
connection and the other is the backup route for the protect
connection.
Between the primary and the backup routes, there are also some
routing strategies as following:
- completely disjoint links;
- completely disjoint nodes;
- completely disjoint SRLGs;
- completely disjoint paths;
In WSON, the RWA procedure of work and protection connections can be
separated into two steps. The RWA of work connection with primary
route is the first step, and the RWA of protection connection with
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backup route is the second one.
If the PCE that performs the AR computation has the function of WA at
the same time, after the computation it will process the WA of the
work connection using the alternate routes which belong to primary
route at first. After designating the terminal one from the
alternate routes of primary route by WA procedure. Sequentially the
PCE will select routes from the alternate routes of back up route
according to the above strategies. Only these routes can be used to
do the WA analysis of the protection connection. After both the WA
analyses have been completed, the PCE will return the correct results
to the PCC. Another scenario is that the PCE has no fucntion of WA
except for the routing computation function. In this case, the PCE
should respond the alternate routes of both primary and backup routes
to the PCC or to the other PCEs which can perform the related WA
process.
5.6. Re-routing of Optimization under AR
The sequenced alternate routes that the related PCE responds will be
saved by the PCC when the original connection is setting up. When
the PCC starts re-routing of optimizing, it can select the optimizing
route from these alternate routes. If all the alternate routes can
not meet the optimizing strategy, the PCC will request another
alternate routes from the PCE, that is, optimizing alternate routes
will replace the old ones. The optimizing strategy is the same as
the sequence strategy of alternate routes that is introduced in "4.2.
AR Extended Constraints".
5.7. Re-routing of Fault Recovery under AR
The mechanism of re-routing of fault recovery under AR is basically
the same as of re-routing of optimization. The difference is that in
re-routing of fault recovery, Control Plane(CP) in WSON will detect
the fault location and inform the PCC. The fault type usually
consists of link fault, node fault and SRLG fault. And the PCC will
add all the detected faults into the exclusion constraints of re-
routing. And the selected alternate routes MUST meet the added
exclusion constraints when re-routing procedure is performed.
5.8. Hierachical Routing in AR Computation
In WSON, especially for AR, hierachical route is also a good
mechanism to enhance routing efficiency. By aggregate routes of
inter-Autonomous System(AS), inter-area, inter-subarea and so on, the
wholly route between the node pair that spans more than one area can
be assembled. Similarly, AR computation can be performed at the same
range level. To some extent, it is similar to the AR process of
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inclusion constraint. The path to be set up is separated into a few
hierarchies by the different ranges. In the ranges of same
hierarchy, alternate routes belonging to different ranges that have
been obtained can be combined together by the designated PCE. The
whole alternate routes in the ranges of same hierarchy will be
include the range border LSRs which the path MUST passes by. If the
numbers of alternate routes belonging to different ranges with same
hierarchy are respectively k1,k2,kn, the number of whole alternate
routes MAY be k1*k2*kn.
6. PCECP Extended Requirements for AR
6.1. Subobject of AR Extended Constraints
The body format of constraint route object is mainly based on
[RFC4874], [draft-ietf-pce-pcep-xro-06], and [draft-ietf-pce-pecp-16]
. Considering inclusion constraint, constraint routing inquiry
strategy(strict or loose constraint), and priority of loose
constraint, the format has been further improved as following.
X
In [draft-ietf-pce-pcep-xro-06], the X-bit indicates whether the
contraint is mandatory or desired. 0 indicates that the resource
specified MUST be excluded from the path computed by the PCE. 1
indicates that the resource specified SHOULD be excluded from the
path computed by the PCE. That is, "MUST" means strict
constraint, and "SHOULD" means loose constraint. And now, X is
extended to indicate whether the exclusion or the inclusion is
mandatory or desired.
Cons. Type
The cons. type of the subobject. The following subobject types
are defined.
- 00 Exclusion constraint of primary route.
- 01 Inclusion constraint of primary route. When the value is 1,
the path MUST or SHOULD include the following subobjects.
- 02 Exclusion constraint of backup route.
- 03 Inclusion constraint of backup route. When the value is 1,
the path MUST or SHOULD include the following subobjects.
Priority
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The priority of the subobject. When X subobject is 1, the
subobject of priority will take effect. It expresses the priority
of loose constraint. The value of priority ranges from 0 to 255
in descending sequence. The higher the priority is, the ealier
the loose constraint will be met.
Reserved
Reserved fields within subobjects MUST be transmitted as zero and
SHOULD be ignored on receipt. It is used to pack allignment and
extended in the furture.
IPv4 prefix Subobject
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type = 1 | Length | Cons. Type | Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | IPv4 address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 address (continued) | Prefix Length | Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 prefix Subobject
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type = 2 | Length | Cons. Type | Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | IPv6 address (16 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address (continued) | Prefix Length | Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Unnumbered Interface ID 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type = 3 | Length | Reserved | Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cons. Type | Priority | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The TE Router ID and Interface ID fields are as defined in
[RFC3477].
Autonomous System Number Subobject
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type = 4 | Length | Cons. Type | Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | 2-Octet AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Note that as in other PCEP objects [PCEP] and RSVP-TE objects
[RFC3209], no support for 4-octet AS Numbers is provided. It is
anticipated that, as 4-octet AS Numbers become more common, both
PCEP and RSVP-TE will be updated in a consistent way to add this
support.
SRLG Subobject
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type = 5 | Length | Cons. Type | Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | SRLG Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRLG Id (continued) | Reserved | Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The Attribute SHOULD be set to two (2) and SHOULD be ignored on
receipt.
6.2. Requset of Alternate Routes
The format of the RP object body in [draft-ietf-pce-pecp-16] 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |O|B|R| Pri |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request-ID-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Flags (24 bits): No Flags are currently defined.
o Pri (Priority - 3 bits): the Priority field may be used by the
requesting PCC to specify to the PCE the request's priority from 1
to 7.
o R (Reoptimization - 1 bit): when set, the requesting PCC specifies
that the PCReq message relates to the reoptimization of an
existing TE LSP.
o B (Bi-directional - 1 bit): when set, the TE LSP is bidirectional.
o O (strict/loose - 1 bit): when set, in a PCReq message, this
indicates that a loose path is acceptable.
o Request-ID-number (32 bits). The Request-ID-number value combined
with the source IP address of the PCC and the PCE address uniquely
identify the path computation request context.
Based on [draft-ietf-pce-pecp-16], the request of alternate routes is
extended as following:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |O|B|R| Pri |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request-ID-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Primary Routes Number Limit | Backup Routes Number Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Primary Routes Seq Stra. | Backup Routes Seq Stra. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Constraint Subobjects //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o O (backup flag - 1 bit): Here, this bit is difined as whether the
request asks alternate backup routes computation.
o Primary Routes Seq Stra. Please see 4.2.3. Sequence Strategy of
Alternate Routes.
o Backup Routes Seq Stra. Please see 4.2.3. Sequence Strategy of
Alternate Routes.
6.3. Response of Alternate Routes
6.3.1. Basic Information Object
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Isbackupflg | Length | Act num of primary Routes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Act num of backup Routes | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Isbackupflg: Whether the PCE need to compute backup routes.
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0 - Backup route disable.
1 - Backup route enable.
Length: The length of the basic information object.
Act num of primary Routes: Actual number of primary routes computed.
Act num of backup Routes: Actual number of primary routes computed.
Reserved: For the purpose of extension.
Optional TLVs: Now, suggested types are the following.
1 - Complexity of time about primary routes.
2 - Complexity of space about primary routes.
3 - Complexity of time about backup routes.
4 - Complexity of space about backup routes.
6.3.2. Alternate Routes Subobjects
In [draft-ietf-pce-pecp-16], it indicates "If the path computation
request can be satisfied (the PCE finds a set of paths that satisfy
the set of constraints), the set of computed paths specified by means
of ERO objects is inserted in the PCRep message." But for AR in
WSON, ERO can be obtained only after WA procedure.
So alternate routes subobjects are defined as following:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Hop |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Next Hops' Information //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Hop |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Next Routes //
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| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute: Primary or backup alternate routes.
0 - Primary alternate routes.
1 - Backup alternate routes.
Length: The total length of actual alternate routes.
Each hop's information is defined:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router Node Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Output Interface Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Residual bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Hop Subobject Body Format for IPv4
The format of the hop subobject for IPv6 (Object-Type=2) is as
follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Router IPv6 address (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router Node Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Output Interface Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Residual bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Hop Subobject Body Format for IPv6
7. Manageability Considerations
Manageability of WSON Alternate Routing (AR) with PCE must address
the following considerations:
7.1. Control of Function and Policy
In addition to the parameters already listed in Section 4.1, a PCECP
implementation SHOULD allow configuring the following PCECP session
parameters on a PCC:
o The ability to send a WSON AR request.
In addition to the parameters already listed in Section 4.1, a PCECP
implementation SHOULD allow configuring the following PCECP session
parameters on a PCE:
o The support for WSON AR.
o The attribute of used algorithm for WSON AR.
o The support of pre-process for WSON AR.
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These parameters may be configured as default parameters for any
PCECP session the PCECP speaker participates in, or may apply to a
specific session with a given PCECP peer or a specific group of
sessions with a specific group of PCECP peers. The policy
configuration interface is yet to be determined. The interface may
be purely a local matter, or it may be supported via a standardized
interface (such as a MIB module).
7.2. Information and Data Models
It is expected that the operations of AR will be modeled and
controlled through appropriate MIB modules. The tables in the new
MIB modules will need to reflect the relationships between entities
and to control and report on configurable options.
Extensions to the PCECP MIB module should be defined, so as to cover
the WSON AR information introduced in this document. A future
revision of this document will list the information that should be
added to the MIB module.
7.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
described in [RFC4655].
7.4. Verifying Correct Operation
Mechanisms defined in this document do not imply any new verification
requirements in addition to those already listed in section 9.4 of
[RFC4655].
7.5. Requirements on Other Protocols and Functional Components
The PCE Discovery mechanisms ([ISIS PCED] and [OSPF PCED]) may be
used to advertise WSON AR path computation capabilities to PCCs.
7.6. Impact on Network Operation
Mechanisms defined in this document do not imply any new network
operation requirements in addition to those already listed in section
9.6 of [RFC4655].
8. Security Considerations
This document has no requirement for a change to the security models
within GMPLS and associated protocols. But the PCE's AR capabilities
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may wish to be kept private. Consideration should be given to
securing this information.
9. IANA Considerations
No new values are specified in this document.
10. Acknowledgments
TBD.
11. References
11.1. Normative References
[G.694.1] ITU-T Recommendation G.694.1, "Spectral grids for WDM
applications: DWDM frequency grid", June 2002.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471,
January 2003.
[RFC3474] Lin, Z. and D. Pendarakis, "Documentation of IANA
assignments for Generalized MultiProtocol Label Switching
(GMPLS) Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) Usage and Extensions for
Automatically Switched Optical Network (ASON)", RFC 3474,
March 2003.
[RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, October 2005.
[RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support
of Generalized Multi-Protocol Label Switching (GMPLS)",
RFC 4203, October 2005.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657,
September 2006.
[RFC4874] Lee, CY., Farrel, A., and S. De Cnodder, "Exclude Routes -
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Extension to Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE)", RFC 4874, April 2007.
11.2. Informative References
[LSR-LS] Otani, T., Guo, H., Miyazaki, K., and D. Caviglia,
"Generalized Labels of Lambda-Switching Capable Label
Switching Routers (LSR)", work in progress:
draft-otani-ccamp-gmpls-lambda-labels-01 , November 2007.
[PCE-PCEP]
Vasseur, JP., Ed, and JL. Le Roux, "Path Computation
Element (PCE) Communication Protocol(PCEP)",
draft-ietf-pce-pcep-16.txt , November 2007.
[PCEP-RE] Oki, E., Takeda, T., and A. Farrel, "Extensions to the
Path Computation Element Communication Protocol(PCEP) for
Route Exclusions", draft-ietf-pce-pcep-xro-06.txt .
[WSON-LC] Zhihong Kang, Zhenyu Wang, and Feng Gao, "Link
Connectivity and Common Constraint Information Extension
to GMPLS for WDM Switched Optical Networks",
draft-lee-pce-wson-routing-wavelength-01 work in progress,
November 2007.
[WSON-RWA]
Lee, Y. and G. Bernstein, "PCEP Requirements and
Extensions for WSON Routing and Wavelength Assignment",
draft-lee-pce-wson-routing-wavelength-01 work in progress.
Authors' Addresses
Dajiang Wang
ZTE Corporation
12thF, ZTE Plaza, No.19 East HuaYuan Road
HaiDian District, Beijing
P.R.China
Phone: +86-10-82963984
Email: wang.dajiang@zte.com.cn
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Zhenyu Wang
ZTE Corporation
12thF, ZTE Plaza, No.19 East HuaYuan Road
HaiDian District, Beijing
P.R.China
Phone: +86-10-82963987
Email: wang.zhenyu1@zte.com.cn
Qimin Xiang
ZTE Corporation
5thF, ZTE Industrial Park, No.8 Building
NanShan District, Shenzhen
P.R.China
Phone: +86-755-26773941
Email: xiang.qimin@zte.com.cn
Feng Gao
ZTE Corporation
12thF, ZTE Plaza, No.19 East HuaYuan Road
HaiDian District, Beijing
P.R.China
Phone: +86-10-82963984
Email: gao.feng1@zte.com.cn
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Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
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Wang, et al. Expires May 1, 2009 [Page 25]