[c-nsp] Circuit Emulation over MPLS

Oliver Boehmer (oboehmer) oboehmer at cisco.com
Wed Feb 15 07:32:58 EST 2006

Sasanka Bella <> wrote on Tuesday, February 14, 2006 11:04 AM:

> Hello,
> We are in the process designing a global enterprise network. One
> requirement is to have PABX interconnectivity where  each remote PABX
> need to be connected to central group switch on ISDN PRI over the
> WAN. The WAN will be ;
> a) either MPLS (L3) over ATM (L2)
> b) or, IP/MPLS (ethernet)
> We would like to understand the better approach (a or b above) to do
> ciruit emulation of ISDN PRI
> Can you please share with us ;
> 1. Advantages/disadvantages of selecting one scenario over the other
> in light of circuit emulation
> 2. Any general issues/concerns with ciruit emulation
> 3. Any documentation or pointers highlighting how we can achive this
> (configuration)

Currently, there are no circuit-Emulation over MPLS adapters available
(unless something has changed *very* recently). So you cannot plug your
PBX E1's directly into a L2VPN or L3VPN PE and send it across the MPLS
core, the timing/clocking will not work.
We have CEoIP network modules available (NM-CEM-4TE1, NM-CEM-4SER), so
you can conncet the PBX to a L3VPN CE device and transport your voice
traffic as IP over an MPLS network (within a vrf or in the global

Another obvious option is Voice-over-IP (for example using QSIG) on CE's
to connect your PBX over an IP network (with or without MPLS)..


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