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New Member

OSPF opaque (MPLS-TE)

I have some question:

1.MPLS traffic engineering use opaque (LSA type 9,10,11) to get eg. BW of the link!

But in OSPF , when there is a change in an area, the LSA will flood to all. So if there is an application transfer a file on the link, the BW will change continuosly (?), so the LSA will flood and how can the CR-LDP know what information about BW on that link to use.

2.In an multi-area OSPF network, which router will start the label distribution process??

3.Is there any document about opaque with MPLS-TE. I try RFC3630 but it's very difficult to understand.

4 REPLIES

Re: OSPF opaque (MPLS-TE)

Hello,

MPLS TE is a pure control plane feature. So:

A1) The announced bandwidth does only change when there is a new "booking". This means that only when a new tunnel is routed over a link, when a tunnel is removed from a link or when a link up/down event occurs flooding is needed. To control the amount of opaque LSAs, thresholds are used for the booking bandwidth value.

The real bandwidth utilized at any moment in time is not taken into account by MPLS TE!

A2) Every MPLS TE enabled router will send LSA 10 and ABRs will insert this info into other areas. So pretty much LSA generation and flooding does not deviate from "normal" OSPF LSAs.

A3) I would also read "RFC 2370, The OSPF Opaque LSA Option".

Hope this helps! Please rate all posts.

Regards, Martin

Cisco Employee

Re: OSPF opaque (MPLS-TE)

Martin,

One comment with regards to A2. The LSA type 10 is limited to the local area and the ABR will not disseminate this information to other areas.

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: OSPF opaque (MPLS-TE)

A1)Thanks.

A2) I asked which router will begin the "label dstribution" process...not about the LSA

Cause I wondered if LSA will flood to all areas to the egress router (this case the egress router create tunnel) .Or each ABR recieved LSA 10 will create tunnel for its area?

Q4)How about LSA type 9,10,11... I begin to read RFC 2370 but may be you can share your knowledge with me?

Cisco Employee

Re: OSPF opaque (MPLS-TE)

A2) mpls te CSPF is area centric. In other words, it doesn't extend beyond the area boundary. Therefore flooding the LSA type 10 beyond the scope in not required.

You can still build inter-area tunnels but this implies that the ABR(s) will need to be involved in performing the CSPF for the areas other than the one where the tunnel head-end resides.

A4) Only the lsa type 10 (area-local scope) is used for MPLS TE.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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