draft-ietf-pce-global-concurrent-optimization-00.txt   draft-ietf-pce-global-concurrent-optimization-01.txt 
Network Working Group Y. Lee Network Working Group Y. Lee
Internet-Draft Huawei Internet-Draft Huawei
Intended status: Standards Track JL. Le Roux Intended status: Standards Track JL. Le Roux
Expires: December 24, 2007 France Telecom Expires: May 5, 2008 France Telecom
D. King D. King
Aria Networks Aria Networks
E. Oki E. Oki
NTT NTT
June 22, 2007 November 2, 2007
Path Computation Element Communication Protocol (PCECP) Requirements and Path Computation Element Communication Protocol (PCECP) Requirements and
Protocol Extensions In Support of Global Concurrent Optimization Protocol Extensions In Support of Global Concurrent Optimization
draft-ietf-pce-global-concurrent-optimization-00.txt draft-ietf-pce-global-concurrent-optimization-01.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
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This Internet-Draft will expire on December 24, 2007. This Internet-Draft will expire on May 5, 2008.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
The Path Computation Element (PCE) is a network component, The Path Computation Element (PCE) is a network component,
application, or node that is capable of performing path computations application, or node that is capable of performing path computations
at the request of Path Computation Clients (PCCs). The PCE is at the request of Path Computation Clients (PCCs). The PCE is
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3.3. Greenfield Optimization . . . . . . . . . . . . . . . . . 9 3.3. Greenfield Optimization . . . . . . . . . . . . . . . . . 9
3.3.1. Single-layer Traffic Engineering . . . . . . . . . . . 10 3.3.1. Single-layer Traffic Engineering . . . . . . . . . . . 10
3.3.2. Multi-layer Traffic Engineering . . . . . . . . . . . 10 3.3.2. Multi-layer Traffic Engineering . . . . . . . . . . . 10
4. PCECP Requirements . . . . . . . . . . . . . . . . . . . . . . 11 4. PCECP Requirements . . . . . . . . . . . . . . . . . . . . . . 11
5. Protocol extensions for support of global concurrent 5. Protocol extensions for support of global concurrent
optimization . . . . . . . . . . . . . . . . . . . . . . . . . 15 optimization . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.1. Global Objective Function (GOF) Specification . . . . . . 16 5.1. Global Objective Function (GOF) Specification . . . . . . 16
5.2. Indication of Global Concurrent Optimization Requests . . 16 5.2. Indication of Global Concurrent Optimization Requests . . 16
5.3. Request for the order of LSP . . . . . . . . . . . . . . . 16 5.3. Request for the order of LSP . . . . . . . . . . . . . . . 16
5.4. The Order Response . . . . . . . . . . . . . . . . . . . . 17 5.4. The Order Response . . . . . . . . . . . . . . . . . . . . 17
5.5. Global Constraints (GC) Object . . . . . . . . . . . . . . 19 5.5. GLOBAL CONSTRAINTS (GC) Object . . . . . . . . . . . . . . 19
5.6. Error Indicator . . . . . . . . . . . . . . . . . . . . . 20 5.6. Error Indicator . . . . . . . . . . . . . . . . . . . . . 20
5.7. NO-PATH Indicator . . . . . . . . . . . . . . . . . . . . 21 5.7. NO-PATH Indicator . . . . . . . . . . . . . . . . . . . . 21
6. Manageability Considerations . . . . . . . . . . . . . . . . . 23 6. Manageability Considerations . . . . . . . . . . . . . . . . . 23
6.1. Control of Function and Policy . . . . . . . . . . . . . . 23 6.1. Control of Function and Policy . . . . . . . . . . . . . . 23
6.2. Information and Data Models, e.g. MIB module . . . . . . . 23 6.2. Information and Data Models, e.g. MIB module . . . . . . . 23
6.3. Liveness Detection and Monitoring . . . . . . . . . . . . 23 6.3. Liveness Detection and Monitoring . . . . . . . . . . . . 23
6.4. Verifying Correct Operation . . . . . . . . . . . . . . . 23 6.4. Verifying Correct Operation . . . . . . . . . . . . . . . 23
6.5. Requirements on Other Protocols and Functional 6.5. Requirements on Other Protocols and Functional
Components . . . . . . . . . . . . . . . . . . . . . . . . 24 Components . . . . . . . . . . . . . . . . . . . . . . . . 24
6.6. Impact on Network Operation . . . . . . . . . . . . . . . 24 6.6. Impact on Network Operation . . . . . . . . . . . . . . . 24
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solutions in support of concurrent path computation applications that solutions in support of concurrent path computation applications that
may arise during network operations. A concurrent path computation may arise during network operations. A concurrent path computation
is a path computation application where a set of TE paths are is a path computation application where a set of TE paths are
computed concurrently in order to efficiently utilize network computed concurrently in order to efficiently utilize network
resources. The computation method involved with a concurrent path resources. The computation method involved with a concurrent path
computation is referred to as global concurrent optimization in this computation is referred to as global concurrent optimization in this
document. Appropriate computation algorithms to perform this type of document. Appropriate computation algorithms to perform this type of
optimization are out of the scope of this document. optimization are out of the scope of this document.
The Global Concurrent Optimization (GCO) application is primarily an The Global Concurrent Optimization (GCO) application is primarily an
NMS based solution. Due to complex synchronization issues associated NMS or a PCE Server based solution. Due to complex synchronization
with GCO application, the management based PCE architecture defined issues associated with GCO application, the management based PCE
in section 5.5 of [RFC4655] is considered as the most suitable usage architecture defined in section 5.5 of [RFC4655] is considered as the
to support GCO application. This does not automatically preclude most suitable usage to support GCO application. This does not
other architectural alternatives to support GCO application, but they automatically preclude other architectural alternatives to support
are not recommended. For instance, GCO may be enabled by distributed GCO application, but they are not recommended. For instance, GCO may
LSRs through complex synchronization. However, this approach may be enabled by distributed LSRs through complex synchronization.
suffer from significant synchronization overhead between the PCE and However, this approach may suffer from significant synchronization
each of the PCCs. It would likely affect the network stability and overhead between the PCE and each of the PCCs. It would likely
hence significantly diminish the benefits of deploying PCEs. affect the network stability and hence significantly diminish the
benefits of deploying PCEs.
As new LSPs are added sequentially or removed from the network over As new LSPs are added sequentially or removed from the network over
time, the global network resources become fragmented and the network time, the global network resources become fragmented and the network
no longer provides the optimal use of the available capacity. A no longer provides the optimal use of the available capacity. A
global concurrent path computation is able to simultaneously consider global concurrent path computation is able to simultaneously consider
the entire topology of the network and the complete set of existing the entire topology of the network and the complete set of existing
LSPs, and their respective constraints, and look to re-optimize the LSPs, and their respective constraints, and look to re-optimize the
entire network to satisfy all constraints for all LSPs. entire network to satisfy all constraints for all LSPs.
Alternatively, the application may consider a subset of the LSPs Alternatively, the application may consider a subset of the LSPs
and/or a subset of the network topology. and/or a subset of the network topology.
The need for a global concurrent path computation may also arise when The need for a global concurrent path computation may also arise when
network operators need to establish a set of TE LSPs in their network network operators need to establish a set of TE LSPs in their network
planning process. It is also envisioned that network operators might planning process. It is also envisioned that network operators might
require a global concurrent path computation in the event of require a global concurrent path computation in the event of
catastrophic network failures, where a set of TE LSPs need to be catastrophic network failures, where a set of TE LSPs need to be
optimally rerouted. The nature of this work does promote such optimally rerouted. The nature of this work does promote such
systems for offline processing. Online application of this work systems for offline processing. Online application of this work
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collocated case there is no need for a standard communication collocated case there is no need for a standard communication
protocol, this can rely on internal APIs. protocol, this can rely on internal APIs.
----------- -----------
Application | ----- | Application | ----- |
Request | | TED | | Request | | TED | |
| | ----- | | | ----- |
v | | | v | | |
------------- Request/ | v | ------------- Request/ | v |
| PCC | Response| ----- | | PCC | Response| ----- |
| (NMS) |<--------+> | PCE | | | (NMS/Server)|<--------+> | PCE | |
| | | ----- | | | | ----- |
------------- ----------- ------------- -----------
Service | Service |
Request | Request |
v v
---------- Signaling ---------- ---------- Signaling ----------
| Head-End | Protocol | Adjacent | | Head-End | Protocol | Adjacent |
| Node |<---------->| Node | | Node |<---------->| Node |
---------- ---------- ---------- ----------
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* During a migration it may not be possible to do a make-before- * During a migration it may not be possible to do a make-before-
break for all existing LSPs. The request message must allow break for all existing LSPs. The request message must allow
indicating for each request whether make-before-break is indicating for each request whether make-before-break is
required (e.g. Voice traffic) or break-before-make is required (e.g. Voice traffic) or break-before-make is
acceptable (e.g. Internet traffic). The response message must acceptable (e.g. Internet traffic). The response message must
allow indicating LSPs for which make-before-break allow indicating LSPs for which make-before-break
reoptimization is not possible (this will be deduced from the reoptimization is not possible (this will be deduced from the
LSP setup and deletion orders). LSP setup and deletion orders).
* During a reoptimization it may be required to move a LSP
several times so as to avoid traffic disruption. The response
message must allow indicating the sequence of successive paths
for each request.
5. Protocol extensions for support of global concurrent optimization 5. Protocol extensions for support of global concurrent optimization
This section provides protocol extensions for support of global This section provides protocol extensions for support of global
concurrent optimization. Protocol extensions discussed in this concurrent optimization. Protocol extensions discussed in this
section are built on [PCEP]. section are built on [PCEP].
The format of a PCReq message is currently as follows per [PCEP]: The format of a PCReq message is currently as follows per [PCEP]:
<PCReq Message>::= <Common Header> <PCReq Message>::= <Common Header>
[<SVEC-list>] [<SVEC-list>]
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tasks: tasks:
1: Remove path P1 1: Remove path P1
2: Setup path P2' 2: Setup path P2'
3: Remove path P2 3: Remove path P2
4: Setup path P1' 4: Setup path P1'
That is, R1 is reoptimized in a break-before-make manner and R2 in a That is, R1 is reoptimized in a break-before-make manner and R2 in a
make-before-break manner. make-before-break manner.
5.5. Global Constraints (GC) Object 5.5. GLOBAL CONSTRAINTS (GC) Object
The Global Constraints (GC) Object is used in a PCReq message to The Global Constraints (GC) Object is used in a PCReq message to
specify the necessary global constraints that should be applied to specify the necessary global constraints that should be applied to
all individual path computations for a global concurrent path all individual path computations for a global concurrent path
optimization request. optimization request.
GLOBAL CONSTRAINT Object-Class is to be assigned by IANA (recommended
value=21)
GLOBAL CONSTRAINT Object-Type is to be assigned by IANA (recommended
value=1)
The format of the GC object body that includes the global constraints The format of the GC object body that includes the global constraints
is as follows: is as follows:
0 1 2 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MU | mU | OB | MH | | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MH | MU | mU | OB |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
// Optional TLV(s) // // Optional TLV(s) //
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: GC body object format
MU (Max Utilization) (8 bits) : 8 bit integer that indicates the Figure 10: GC body object format
upper bound utilization percentage by which all link should be bound.
Utilization = (Link Capacity - Allocated Bandwidth on the Link)/ Link
Capacity
mU (minimum Utilization) (8 bits) : 8 bit integer that indicates the MH (Max Hop: 8 bits): 8 bit integer that indicates the maximum hop
lower bound utilization percentage by which all link should be bound. count for all the LSPs.
OB (Over Booking factor) (8 bits) : 8 bit integer that indicates the MU (Max Utilization Percentage: 8 bits) : 8 bits integer that
overbooking percentage that allows the reserved bandwidth to be indicates the upper bound utilization percentage by which all link
overbooked on each link beyond its physical capacity limit. The should be bound. Utilization = (Link Capacity - Allocated Bandwidth
value, for example, 10% means that 110 Mbps can be reserved on a on the Link)/ Link Capacity
100Mbps link.
MH (Max Hop) (8 bits): 8 bit integer that indicates the maximum hop mU (minimum Utilization Percentage: 8 bits) : 8 bits integer that
count for all the LSPs. indicates the lower bound utilization percentage by which all link
should be bound.
GC Object-Class is to be assigned by IANA. OB (Over Booking factor Percentage: 8 bits) : 8 bits integer that
indicates the overbooking percentage that allows the reserved
bandwidth to be overbooked on each link beyond its physical capacity
limit. The value, for example, 10% means that 110 Mbps can be
reserved on a 100Mbps link.
GC Object-Type is to be assigned by IANA. Reserved bits (24 bits) of the GLOBAL CONSTRAINTS Object SHOULD be
transmitted as zero and SHOULD be ignored upon receipt.
The exclusion of the list of nodes/links from a global path The exclusion of the list of nodes/links from a global path
computation can be done by including the XRO object following the GC computation can be done by including the XRO object following the GC
object in the new SVEC list definition. object in the new SVEC list definition.
5.6. Error Indicator 5.6. Error Indicator
To indicate errors associated with the global concurrent path To indicate errors associated with the global concurrent path
optimization request, a new Error-Type (14) and subsequent error- optimization request, a new Error-Type (14) and subsequent error-
values are defined as follows for inclusion in the PCEP-ERROR object: values are defined as follows for inclusion in the PCEP-ERROR object:
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Two new bit flags are defined in the NO-PATH-VECTOR TLV carried in Two new bit flags are defined in the NO-PATH-VECTOR TLV carried in
the NO-PATH Object: the NO-PATH Object:
0x08: when set, the PCE indicates that no migration path was found. 0x08: when set, the PCE indicates that no migration path was found.
0x10: when set, the PCE indicates no feasible solution was found that 0x10: when set, the PCE indicates no feasible solution was found that
meets all the constraints associated with global concurrent path meets all the constraints associated with global concurrent path
optimization in the PCRep message. optimization in the PCRep message.
When either 0x08 or 0x10 flag is set in the NO-PATH-VECTOR TLV
carried in the NO-PATH object in the PCRep Message, a subsequent
multi-session feature may be triggered if the PCC's local policy
allows it. The multi-session feature allows the original global
concurrent optimization to be split into a number of multiple
sessions so that the PCE would compute a number of smaller-scale
optimizations in a sequential manner. The trade-off is that a
partial feasible solution may be obtained using this approach which
is better than not having any solution at all, although such solution
might not be a global optimal solution. How to divide up the
original set of global concurrent optimization requests into multiple
numbers of smaller-scale optimizations is out of the scope of this
document.
6. Manageability Considerations 6. Manageability Considerations
Manageability of Global Concurrent Path Computation with PCE must Manageability of Global Concurrent Path Computation with PCE must
address the following considerations: address the following considerations:
6.1. Control of Function and Policy 6.1. Control of Function and Policy
In addition to the parameters already listed in section 8.1 of In addition to the parameters already listed in section 8.1 of
[PCEP], a PCEP implementation SHOULD allow configuring the following [PCEP], a PCEP implementation SHOULD allow configuring the following
PCEP session parameters on a PCC: PCEP session parameters on a PCC:
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