Jumbo frame Question

Joel Jaeggli joelja at bogus.com
Fri Nov 26 15:29:45 CST 2010


10/100 switches and NICs pretty much universally do not support jumbos.

Joel's widget number 2

On Nov 26, 2010, at 8:02, Brandon Kim <brandon.kim at brandontek.com> wrote:

> 
> Where would the world be if we weren't stuck at 1500 MTU? I've always kinda thought, what if that was larger 
> from the start....
> 
> We keep getting faster switchports, but the MTU is still 1500 MTU! I'm sure someone has done some testing with
> a 10/100 switch with jumbo frames enables versus a 10/100/1000 switch using regular 1500 MTU and compared
> the performance.....
> 
> 
> 
> 
>> Subject: RE: Jumbo frame Question
>> Date: Thu, 25 Nov 2010 21:14:02 -0800
>> From: gbonser at seven.com
>> To: harris.hui at hk1.ibm.com; nanog at nanog.org
>> 
>>> Hi
>>> 
>>> Does anyone have experience on design / implementing the Jumbo frame
>>> enabled network?
>>> 
>>> I am working on a project to better utilize a fiber link across east
>>> coast
>>> and west coast with the Juniper devices.
>>> 
>>> Based on the default TCP windows in Linux / Windows and the latency
>>> between
>>> east coast and west coast (~80ms) and the default MTU size 1500, the
>>> maximum throughput of a single TCP session is around ~3Mbps but it is
>>> too
>>> slow for us to backing-up the huge amount of data across 2 sites.
>> 
>> There are a lot of stack tweaks you can make but the real answer is
>> larger MTU sizes in addition to those tweaks.  Our network is completely
>> 9000 MTU internally. We don't deploy any servers anymore with MTU 1500.
>> MTU 1500 is just plain stupid with any network >100mb ethernet.
>> 
>>> The following is the topology that we are using right now.
>>> 
>>> Host A NIC (MTU 9000) <--- GigLAN ---> (MTU 9216) Juniper EX4200 (MTU
>>> 9216)
>>> <---GigLAN ---> (MTU 9018) J-6350 cluster A (MTU 9018) <--- fiber link
>>> across site ---> (MTU 9018) J-6350 cluster B (MTU 9018) <--- GigLAN
>> ---
>>>> 
>>> (MTU 9216) Juniper EX4200 (MTU 9216) <---GigLAN ---> (MTU 9000) NIC -
>>> Host
>>> B
>>> 
>>> I was trying to test the connectivity from Host A to the J-6350
>> cluster
>>> A
>>> by using ICMP-Ping with size 8000 and DF bit set but it was failed to
>>> ping.
>>> 
>>> Does anyone have experience on it? please advise.
>>> 
>>> Thanks :-)
>> 
>> You might have some transport in the path (SONET?) that can't send 8000.
>> I would try starting at 3000 and working up to find where your limit is.
>> 
>> Your description of "fiber link across site" is vague. Who is the
>> vendor, what kind of service?  
>> 
>> 
>                         
> 




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