DFC3s for MPLS ?

Answered Question
Mar 3rd, 2009

I'm looking for some advice on running MPLS on the 6500 platform. I've got several 6500's with Sup 720 (PFC 3A) which I am looking to upgrade to PFC 3Bs to support MPLS. However, I'm wondering if I should upgrade the modules to DFC3's to support MPLS. I imagine that the answer might be "it depends", but thought I would reach out for advice.


Anyone have recommendations or links that might help with this decision?


Thanks,

Jim


Correct Answer by Edison Ortiz about 7 years 12 months ago

If your current modules are classic line cards, moving to DFC3 enabled line cards will dramatically increase the throughput in the switch, not just for MPLS.


Instead of me rambling about all the benefits of moving away from classic line cards to DFC3 enabled line cards, I recommend reading this comprehensive article on the 6500 architecture.


http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd80673385.html


HTH,


__


Edison.

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Correct Answer
Edison Ortiz Tue, 03/03/2009 - 09:54

If your current modules are classic line cards, moving to DFC3 enabled line cards will dramatically increase the throughput in the switch, not just for MPLS.


Instead of me rambling about all the benefits of moving away from classic line cards to DFC3 enabled line cards, I recommend reading this comprehensive article on the 6500 architecture.


http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd80673385.html


HTH,


__


Edison.

jim_berlow Tue, 03/03/2009 - 10:55

Thanks, Edison - very useful link.


Having read the info on that link I now have another question. I have a CAT 6513 with a WS-X6724-SFP module in slot 1 (non-fabric enabled slot obviously). First, I'm kind of surprised that it is even working there. It must be running at a slower line rate w/o the fabric connection through the Sup 720.


Would it even do any good to add a DFC-3B to this module in its current location or do I need to move it to a fabric enabled port (9-13) for this to even do any good?


Thanks for your help - that was a very insightful link!


Jim

Edison Ortiz Tue, 03/03/2009 - 11:17

Jim,


WS-X6724-SFP when upgraded to a DFC3 enabled module, will be a dual-fabric module.


On the link, Table 1, dual-fabric modules will need to be on 9-13.


If the module was to be a single fabric module, yes there are some out there, then you can use any slot.


Joseph W. Doherty Tue, 03/03/2009 - 12:33

All 6513 slots have fabric connections with sup720, but only slots 9-13 have dual fabric connections.


As to why WS-X6724-SFP works in slot1, from http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/product_data_sheet0900aecd801459a7.html:

• Backplane connection: Connects to the switch fabric using dual full duplex 20 Gbps switch fabric channels (40 Gbps total), a single 20 Gbps channel is supported by the WS-X6724-SFP


DFCs provide local, on card, forwarding (dCEF), i.e. more PPS. Not exactly the same issue as bandwidth available to the card.

Jon Marshall Tue, 03/03/2009 - 14:26

Jim


Just to add to Joseph's point. A Sup720 delivers a 720Gbps switching fabric.

Just to complicate things when Cisco talk of module connections they don't use full duplex figures ie.

a 6708 has 2 x 20Gbps connections to the switch fabric which is 40Gbps total. But at full duplex this

is 80Gbps.


So for a 6509 chassis a Supervisor 720 can provide 40Gbps to each slot ie. 9 x 40 = 360. To get the full

duplex figure you then double that number ie. 360 x 2 = 720.


For a 6513 chassis you cannot have every slot providing 40Gbps because this would work out as


13 x 40 = 520 x 2 = 1040Gbps.


But as previously stated the Sup720 can only provide 720Gbps. So the first 8

slots can only provide a 20Gbps connection maximum to the switch fabric and then 9-13 provide 40Gbps ie.


8 x 20 = 160

5 x 40 = 200


160 + 200 = 360 * 2 = 720


So as Joseph states the WS-X6724-SFP is still connected to the switch fabric but as it only supports one 20Gbps

connection it can go in any slot.


Jon



jim_berlow Wed, 03/04/2009 - 14:52

Thanks - so just to follow up on this. I can leave the 6724-SFP in slot 1 and upgrade it with a DFC3b and I will get full performance?


(I don't need to have that module installed into a dual fabric slot on the 6513 slot 9-13)?


Thanks,

Jim

Edison Ortiz Wed, 03/04/2009 - 14:53

Jim,


That's correct. All slots in the 6513 support single fabric modules such as 6724-SFP.


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Edison

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