6704 vs 6708

[ciscors]

http://www.cisco.com/en/US/products/hw/switches/ps708/products_data_sheet09186a00801dce34.html

I looked up the 10gigabit datasheet for the 6500's but it doesn't have anything in terms of oversubscription. It only states that Port Buffers for the 6704 is 16mb while the 6708 is 200mb.

1) What do port buffers mean

2) Do these modules have groups of ports connected to a single ASIC similar to the 6548 modules which connect ports 1-8 to one ASIC and so on.

3) Or is it as simple as considering that since both these modules have 40gb connections to the backplane, the 6704 provides 10gb to each port, hence no oversubscription while the 6708 has 8 ports which totally have to share 40gbps hence an oversub of 2:1

My final application for this is to link up my distribution switches to the core

Thank you

[Jon Marshall]

Oops, apologies Edison, that will teach me to be more thorough :-)

[Edison Ortiz]

No need to apologize, it was in jest :)

You've made excellent points on this thread and you've corrected several mistakes in my postings. Thanks !

[Edison Ortiz]

You are correct, I misspoke. I was trying to say the Supervisor.

I found this very good link

http://www.cisco.com/en/US/products/hw/switches/ps708/products_white_paper0900aecd80673385.shtml

Edit: Oops, already posted by Arivudainambi

[ciscors]

That's a pretty good link and reading the two examples at the end for CFC & DFC, it seems that only the source line card needs to support DFC (DESTINATION doesn't have to)

1) Read last example on that page and tell me if you agree

2) And now I also understand that data travelling between line cards is always passed through the fabric; however the lookup need not involve the supervisor

3) Can CFC line cards be upgraded at a later time by adding daughter DFC modules or do they have to be completely replaced?

4) I'm a little confused about when to use DFC vs CFC. After all, any traffic will always have a source & destination off one of the line blades (except when I'm using the supervisor GBIC slots). Hence, are there any particular applications I would use one over the other? My SE seemed to suggest that I should use it for cluster servers, etc but I don't understand that clearly

Thank youu

[Jon Marshall]

Hi

1) Yes that's the way i read it as well.

2) Correct. DFC no data to supervisor. CFC - depends on the switching mode of the 6500 ie bus/truncated/compact

3) Yes except classic linecards are not upgradeable.

4) As already pointed out using DFC even if the data needs to go across the switch fabric means the forwarding decision is made on the local card.

If you have servers that require very high throughput then it would make sense to put these on the same module with DFC enabled.

Be aware that when you start mixing CFC, DFC cards + fabric enabled / classic performance will start to degrade.

HTH

Jon

[ciscors]

I'm getting the 6708 for my core and that line blade has no CFC option at all hence it's automatically DFC.

The ports on this line blade connect to the server farm block switches as well as distribution switches. Not sure if this is a good application though but I'm sold on the 6708 anyways so DFC is like an add-on benefit. For servers, I'm going to stick to CFC but tell the customer that a further analysis done in the design phase may warrant doing DFC and if so, we'll simply upgrade the WS-6748-GE-TX cards with daughter cards

[ciscors]

Is there a command on the SUP2 which can tell me how many mpps packets are passing through each line blade or in total on the fabric?

[nambi_gct]

Please try "show fabric utilization"

http://www.cisco.com/en/US/products/hw/switches/ps708/products_command_reference_chapter09186a00801eaf05.html#wp1183031

HTH.