mohammedmahmoud Fri, 05/04/2007 - 22:29
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Hi Jimmy,

To do MPLS TE, basically every LSR must have the entire network topology which can be done only via using OSPF or ISIS (as they are the only IGPs that hold the entire topology) --> Accordingly OSPF or ISIS with MPLS TE extensions is needed.

OSPF and ISIS MPLS TE extensions can propagate available resources and constraints of all network links.

Either RSVP or CR-LDP can be used to create the TE tunnel and propagate the TE Labels in the control plane.

NOTE: Because RSVP with TE extensions takes care of the distribution of the MPLS labels, you do not need to configure Label Distribution Protocol (LDP) on the interfaces. Therefore, the MPLS network does not strictly need to have mpls ip on the interfaces, if TE is deployed. However, if you do not deploy TE to carry all traffic from ingress LSRs to egress LSRs, you need LDP to avoid unlabeled traffic in the core network. MPLS VPN traffic, for instance, needs to be labeled at all times in the core network.

HTH, please do rate if it does help,

Mohammed Mahmoud.

Harold Ritter Sat, 05/05/2007 - 09:37
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I agree with you that support for OSPF or ISIS MPLS TE extensions is generally required to setup a TE tunnel. The verbatim feature is the exception though.


Harold Ritter Sat, 05/05/2007 - 09:34
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It is not possible to setup a TE tunnel without RSVP since RSVP is the machanism to exchange the labels between the LSRs.

It is possible though to configure TE tunnels without OSPF/ISIS using the verbatim keyword on the explicit path-option as follow

interface Tunnel0

tunnel mpls traffic-eng path-option 1 explicit name tunnel1 verbatim

This basically disables the requirement to run CSPF before setting up the LSP.

Please refer to the following document for more information on the verbatim feature:

Hope this helps,

mohammedmahmoud Sat, 05/05/2007 - 09:38
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Hi Harold,

Perfect answers as usual :)


Mohammed Mahmoud.

jemekeren Sun, 05/06/2007 - 20:51
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great answer,tx for all. BTW how rsvp congestion management is made on the tunnel? for example on the tunnel just made we need to prioritize voice while leaving 2 class (http & stmp) with specified percentage bw usage? tx


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