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MLN Multi-Layer Networks. CCAMP WG, IETF 68 March 2007. MLN document set. Requirements. draft-ietf-ccamp-gmpls-mln-reqs-02. Analysis. draft-ietf-ccamp-gmpls-mln-eval-02. GMPLS Protocol Extensions. draft-papadimitriou-ccamp-gmpls-mrn-extensions-03 draft-ietf-ccamp-mpls-graceful-shutdown

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Mln multi layer networks

MLNMulti-Layer Networks

CCAMP WG, IETF 68

March 2007


Mln document set
MLN document set

Requirements

draft-ietf-ccamp-gmpls-mln-reqs-02

Analysis

draft-ietf-ccamp-gmpls-mln-eval-02

GMPLS Protocol Extensions

draft-papadimitriou-ccamp-gmpls-mrn-extensions-03

draft-ietf-ccamp-mpls-graceful-shutdown

draft-ietf-ccamp-lsp-hierarchy-bis


Analysis summary
Analysis Summary

  • Four areas, where extensions of GMPLS protocols and procedures are required, have been identified

    • GMPLS signaling extension for the setup/deletion of virtual TE-links

    • GMPLS routing and signaling extension for graceful TE-link deletionAli, Z., Zamfir, A., "Graceful Shutdown in MPLS Traffic Engineering Network", <draft-ietf-ccamp-mpls-graceful-shutdown>, work in progress.

    • GMPLS signaling extension for constrained multi-region signaling (SC inclusion/exclusion)

    • GMPLS routing extension for the advertisement of the internal adaptation capability of hybrid nodes.


Solution doc
Solution doc

  • Currently three protocol extensions defined

    • Routing extensions for the advertisement of the Internal Adaptation Capabilities:

      • IACD sub-TLV to be carried within the ISIS Extended IS Reacheability TLV or the OPSF Link TLV

    • Signaling extensions for SC inclusion exclusion

      • A new SC subobject to be carried within the ERO and XRO


Detailed analysis of virtual te link function
Detailed analysis of virtual TE link function

  • Two approaches

    • Soft-FA: LSP signaled but data plane resources not committed => Could rely on procedures similar to secondary LSPs (shared meshed restoration)

    • Remote Association: LSP not signaled, TE link ids and parameters exchanged between FA end-points => Could rely on extensions to the Call procedure (with Notify messages)

  • Pros and cons are discussed

    • Soft FA: More admission control capabilities, but scalability limitations

    • Remote Association: Scales well but less admission control


Received comments
Received comments

  • We privately received comments in two areas.

    • Path diversity / SRLG inheritance

    • Directionality of adaptation information

      • Whether it is from "first SC" to "second SC" or from "second SC" to "first SC" is determined based on SC hierarchy:

Network element

.............................

: -------- :

: | PSC | :

Link1 -------------<->--|#a | :

: +--<->---|#b | :

: | -------- :

TDM : | ---------- :

+PSC : +--<->--|#c TDM | :

Link2 ------------<->--|#d | :

: ---------- :

:............................

Figure 5a. Hybrid node.


Next step
Next step

  • Two documents are close to WG last call.

    • Critical review and comments are appreciated.

    • We propose to WG last call after another spin.

  • We propose to solution doc as WG doc

    • SC incl/excl, adaptation, and virtual TE-link,

2007

2008

10

1

4

7

10

1

3

ietf 68

ietf 69

ietf 70

ietf 71

Requirements

WG Last call

02

03

Evaluation

WG Last cal

02

03

SC incl/excl, AdvrAdaptCap, Virtual TE-link

Solution

WG Last call

03

04

00

01

graceful TE-link shutdown

02

hierarchy-bis

01

02



Virtual te link
Virtual TE-link

  • Two approaches:

    • Soft FA approach: FA-LSP established in the control plane without actually activating cross connections in the data plane.

      • requires state maintenance on all transit LSRs (N square issue)

      • allows for admission control

      • Soft-FA LSPs may be setup using procedures similar to GMPLS P&R procedures for setting up secondary LSPs

    • Remote Association approach: No end-to-end signaling. Exchange of virtual TE-links ids and parameters directly between TE- link end points.

      • does not require state maintenance on transit LSRs, but reduces admission control capabilities

      • association between Virtual TE-link end-points may be based on extensions to the RSVP-TE Call procedure


Graceful te link deletion
Graceful TE-link deletion

  • When a TE-link deletion is planned, we want to gracefully disable Traffic Engineering on the TE Link to avoid traffic disruption.

    • The impact on the traffic flows carried over the TE-link is minimized by triggering notifications so as to gracefully reroute such flows before the TE-link is deleted.

  • Disabling the resource in the control plane and removing the resource for forwarding.

    • The node initiating the graceful shutdown condition SHOULD delay the removal of the resources for forwarding.

    • The control plane should gracefully divert the traffic away from the resource being gracefully shutdown.

  • Two approaches:

    • RSVP-TE Signaling Mechanism

      • Path-Error or Notify is used with “local link maintenance on TE Link required” to convey the information to the LSRs along the TE-link and not to all nodes in the network.

    • OSPF/ ISIS Mechanisms

      • Originate the TE LSA/LSP with Traffic Engineering metric set to 0xffffffff, 0 as unreserved bandwidth/Max LSP bandwidth to discourage all nodes in the area to establish new LSPs through the TE-link.

  • Ali, Z., Zamfir, A., "Graceful Shutdown in MPLS Traffic Engineering Network", <draft-ietf-ccamp-mpls-graceful-shutdown>, work in progress.


Isc inclusion exclusion
ISC inclusion/exclusion

  • Applying FA creation procedure [RFC 4206] in MRN environments can lead to setup one-hop FA-LSPs between each node

    • Extensions to existing RSVP-TE procedures are required e.g. indication of these SC values in a new sub-object of the eXclude Route Object (XRO)

    • Such information can be specified by explicitly indicating which SCs have to included or excluded before initiating the procedure described

    • This solves ambiguous selection of SC to be used along a given segment of the path (and provides possibility to optimize resource usage on a multi-region basis)

2

5

D1

link terminates PSC_1 only

S

0

1

3

6

8

link terminates PSC_2 + LSC

4

7

D2

  • Outgoing explicit route from node S: [0,1,3,6,8,D1] to setup PSC_2 LSP from S to D1

  • At node 0: route selection is PSC_2 LSP [1,3,6,8,D1]

  • At node 1: solution scope for route selection is either LSC LSP [3] [3,6], [3,6,8] or [3,6,8,D1] before continuing PSC_2 LSP signaling


Adaptation capability

L2SC

HO-SDH

OTH

Fiber 1

Fiber 1

Fiber N

Fiber N

Adaptation capability

  • ISCD alone does not allow remote LSR to deduce intermediate termination capabilities of Multiple SC systems => Termination issues (blocking case)

  • Introduction of Interface Adaptation Capability Descriptor (IACD)

  • As part of TE Link_1 advertisement

    • ISCD sub_TLV 1 for L2SC

    • ISCD sub_TLV 2 for HO-SDH

    • ISCD sub_TLV 3 for OTH

    • IACD sub_TLV 1 for L2SC to HO-SDH

  • if no bundling of [1…N]

  • As part of TE Link_N advertisement

    • ISCD sub_TLV 1 for L2SC

    • ISCD sub_TLV 2 for HO-SDH

    • ISCD sub_TLV 3 for OTH

    • IACD sub_TLV 1 for L2SC to HO-SDH


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