ACE Jumbo frames

[syakshanulla]

Hi,

I know ACE support Jumbo frames, But do we see any issue of using jubmo frames like resource consuming and etc?

Also to enable , MTU command needs to be issued in Gloabal level or Interface level?

[pevaneyn]

Hi,

Jumbo frames must be configured using the 'mtu' command at interface level.

Regarding resource usage jumbo frames can have an effect on the resource usage if you use L7 load-balancing, if only due to the higher throughput. There should not be any unexpected resource usage. Of course try to test this before using it in production...

Best regards, Peter

[syakshanulla]

Thanks Peter, I am having ACE Module and running on Bridge mode so i am assuming Jumbo frames should be configured under BVI Interface or Vlan interface?

Just wondering is it really required in ACE to cofnigure Jumbo frames when MSFC configured with Jumbo frames?

if we dont configure Jumbo in ACE and when MSFC (Cat6K) configured with Jumbo frames, will it cause any performance issue?

[pevaneyn]

You need to configure the larger MTU on the vlan interfaces. The BVI is only there to configure the IPs used by the ACE.

Please do read the note related to the L7 policies at:

http://www.cisco.com/en/US/docs/interfaces_modules/services_modules/ace/vA4_1_0/configuration/rtg_brdg/guide/vlansif.html#wp1007281

If you do not configure the vlan interfaces of the ACE to use a higher MTU it can drop unexpected jumbo packets. The sender might start resending traffic with a lower packet size, but not all systems do this.

Best regards, Peter

[Marko Leopold]

And i guess you should increase the TCP buffer size too. Because you have increased packet size you need an increased buffer too.

[syakshanulla]

Hi Marko.

How to increase TCP buffer size and is it really compulsory to do that when we implement Jumbo frames?

[Marko Leopold]

You can look here!

http://www.cisco.com/en/US/docs/interfaces_modules/services_modules/ace/v3.00_A1/configuration/security/guide/tcpipnrm.html#wp1070115

[pevaneyn]

Setting the mss advertised by the ACE with "set tcp mss max" is actually more important.

Otherwise the systems will not take advantage of the bigger mss if the ACE is doing anything at L7.

Due to the higher transfer speeds indeed you should investigate if you need to increase the tcp buffer from the default of

32768 bytes.

Best regards, Peter

[alexgeaney]

Any other suggestion? we had a similiar problem and our Tcp buffer has been increased already.

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