The MPLS WG Archive

[Geoff Bennett <geoff.bennett@marconi.com>]

Hi Niels,

There may be some confusion arising depending on how you configure the ATM
switch.  In effect there are three modes of operation for this device...

1.  Pure ATM.  In this case the switch will operate UNI and NNI interfaces,
and will run PNNI as its routing protocol (PNNI is both an IGP and EGP).
UNI and PNNI signalling will happen on VCI 5.

2.  Pure MPLS.  In this mode, there is no ATM signalling, and no PNNI.
MPLS routing and signalling (OSPF, ISIS, CR-LDP, RSVP-TE, etc.) will pass
over VCI 32 (note, please check the latest draft for the actual VCI number,
it's a while since I read this info).

3.  Ships in the Night (SIN).  In this case, both ATM and MPLS Control
Planes operate simultaneously.  ATM signalling happens on VCI 5, and MPLS
signalling on VCI 32.  VCs that are set up as a result of signalling are
"owned" by one or other of these control planes.   SIN would allow an
operator to continue to run high revenue voice services (and maybe existing
Frame Relay or native ATM services...they make money too)  over the ATM
"character" of the switch.  They can then run the loss-making Internet
services over the MPLS character.


I think there are ideas floating around about a more integrated control
plane for ATM/MPLS switches based on PNNI, but I don't think these have
made it to draft as yet.

Cheers,
Geoff



At 10:02 18/04/01 +0200, MP LS wrote:
>Hello all,
>
>I have some questions becasue something is verry strange to me.
>I just assumed that ATM-LSRS used an IP routing protocol (IGP) just for 
>finding the topology of the network.
>
>But last i read an doccument and there they described that When you change 
>an ATM switch to an ATM-LSR it will use PNNI instead of a IGP for IP. Can 
>anyone make this clear for me??
>
>Thanks a lot.
>
>Greetings,
>
>Niels Sitters.
>
>
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Geoff Bennett                             								Tel: (33) 497 21 43 62
Director of Technology, OCTO               						Fax: (33) 497 21 43 50
Marconi
Gaia - Bat. E                           					email: geoff.bennett@marconi.com
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