09-07-2008 02:39 PM
Hi Guys,
i am just trying to get mt head around this technology. i am trying to configure a LC-ATM interface on a 3640 router. which is connected to a LS1010 switch. MPLS is running in the network.
here is the configuration.
interface ATM3/0.1 tag-switching
ip address 150.1.101.6 255.255.255.0
mpls label protocol tdp
tag-switching atm control-vc 1 64
tag-switching ip
.. i just want to know when do we use MPLS atm vpi 101-103 command
Please note:- 101 and 103 and random numbers . for an example.
and can we use mpls atm control-vci and mpls atm vpi x-y command at the same time . or only 1 command at a time.
Regards
amit
09-08-2008 09:28 AM
Hello Amit,
you actually need to use both:
mpls atm control-vci provides the pvc for signalling: here mpls labels are assigned on demand when traffic needs to be set
mpls atm vpi x-y: provides the VP space where the SVC = MPLS labels are assigned on demand
the first is required for signaling
the second provides the MPLS forwarding resources.
Here you can see the mpls distinction of control plane and forwarding plane that comes from ATM itself.
Hope to help
Giuseppe
09-08-2008 02:14 PM
Hi ,
whats the difference between Mpls atm vpi 101-103
and MPLS atm vpi 101 vci range 33-65000
commands ?
09-08-2008 10:35 PM
Hello Amit,
each ATM cell 53 bytes size has a 5 byte header that contains the fields
vpi
vci
a pvc or svc is identified by vpi/vci that can change at each ATM switch hop (just as MPLS labels for LSPs)
So the difference is that with the first command the SVCs built by MPLS signalling plane can have
vpi = 101 or 102 or 103
vci= any possible value
in the second case:
vpi= 101
vci = 33 to 65000
both commands provides forwarding resources but the first one should provide a bigger label (vpi/vci) space
Hope to help
Giuseppe
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