MPLS VPN Design with very fast convergence

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Nov 3rd, 2008
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I'm currently working on a Design for a MPLS VPN with very fast convergence times.

We have the goal to reach a maximum convergence time of 1,5 seconds when a singel error occurs.

In the Backbone I try to work with FRR (FastReRoute). Between PE and CE I'm not sure what protocol to use. I'm also thinking about L3VPN or L2VPN solution.

Are there any informations, whitepapers, designs about sutch a solution in the web?

Do somebody have experience with sutch convergence times in a MPLS environment?

Thanks and best regrads,


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devang_etcom Mon, 11/03/2008 - 13:07
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MPLS FRR provides 50ms of failover in backbones and about CE-PE you can have ISIS or OSPF protocol to work on, you can check for the BFD feature of the protocol, as well as OSPF and ISIS both support the fast hellos also, so you can try that too!!!

Talking about Layer-3 and Layer-2 vpns you can have both types of vpns carrying on MPLS TE so you can have benefit of FRR!!!


Devang Patel

Giuseppe Larosa Mon, 11/03/2008 - 23:56
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Hello Peer,

MPLS TE FRR helps to provide a reliable fast converging PE to PE path.

PE-CE communication:

if a protocol different then BGP is used the time needed to redistribute into BGP and from BGP into the IGP has to be taken in account.

If both PE and CE support BFD I would point to the usage of an eBGP session + BFD.

However, you deal with the various scanning timers that can be reduced but I don't think they can be subsecond.

An MPLS L2 solution may be faster and can be routed over MPLS TE so that FRR is still used in the core.

For example in the following MPLS design for enterprise a L2 transport service is also considered.


another example including multicast VPN and L3 VPN

that states that MP-BGP convergence is similar to BGP convergence time.

For BFD use with BGP see

Hope to help


ramprasadd Tue, 11/04/2008 - 04:14
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TE-FRR is definately a good option for fast convergence(sub second).To achieve <50ms convergence you need to select right hardware like cards with LoS feature(SIP-600,WS-6704 etc) otherwise TE-FRR convergence time will be in multiples of 100ms.. we observed 300ms(again it is dependent on Box what you select).

Another key thing is either you select TE-FRR or IGP with BFD, using TE-FRR and BFD doesn't make any sense.


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