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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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