Can different IP mtu cause Network Latency

Unanswered Question
Aug 22nd, 2008
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Hi Master


I have vpn tunnel from our HQ to remote site. Can different mtu value caue Network latency. At our HQ it use IP mtu 1350 and remote site use ip mtu 1400. Please advise.


ThanksS

Sai

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Edison Ortiz Fri, 08/22/2008 - 15:23
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Sai,


Having different MTUs can produce packet fragmentation end-to-end. When a device has to fragment a packet, it takes away CPU cycles hence there is a slight network latency penalty.


You can also run into applications that can't be fragmented and this can cause the packet to be dropped.


Try to have the same MTU value - end-to-end.


HTH,


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Edison.

J2NoomSai_2 Fri, 08/22/2008 - 15:47
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Thanks Edison.


We have WAE also no both side. Some people said MTU on WAE should be less than MTU on VPN router. Is that true? Or they should be the same.


Thanks

Sai

Edison Ortiz Fri, 08/22/2008 - 18:36
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WAE is outside my expertise so I can't say for sure.


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ropethic Sun, 08/24/2008 - 04:30
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Sai,

Setting MTU lower is only a requirement when using wccp as redirection method. prior to 4.013 this was a manual setting via GUI and CLI.

I have attached a reference pdf file that explains in detail.



Rob



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