Re: JUMBO FRAMES

1518 is normal. That's your 1500 byte IP packet plus 18 bytes of Ethernet overhead. If the IP packet is 1518 then it's a Baby Giant. MTU probably isn't your issue.

HTH,

Brian McGahan, CCIE #8593 (R&S/SP/Security)
bmcgahan_at_INE.com

Internetwork Expert, Inc.
http://www.INE.com

On Jun 8, 2011, at 8:44 PM, "Bernard Steven" <buny.steven_at_gmail.com> wrote:

> It is a tcp based app. Communication is within the same vlan . For routed
> traffic , i am sure MSS won't be negotiated above PMTU. But for traffic
> between the same VLAN , does some thing like that happen(PMTU) ?
> I am using AIX iptrace + wireshark.
>
> Switch isn't configured for Jumbo frames and i see server sending frames >
> 1500.
>
> In case of Jumbo frames + TCP , do both parties agree on a larger MSS in SYN
> ?
>
> Also do they need rfc 1323 (Win scale) agreed ?
>
>
>
>
>
>
>
> On Thu, Jun 9, 2011 at 2:39 AM, Marko Milivojevic <markom_at_ipexpert.com>wrote:
>
>> Those retransmissions are implemented on the application layer and may
>> not be seen as such unless you were specifically looking for them. On
>> the other hand, TCP retransmissions will be immediately identified as
>> such. Have you ever used tcpdump?
>>
>> --
>> Marko Milivojevic - CCIE #18427
>> Senior Technical Instructor - IPexpert
>>
>> FREE CCIE training: http://bit.ly/vLecture
>>
>> Mailto: markom_at_ipexpert.com
>> Telephone: +1.810.326.1444
>> Web: http://www.ipexpert.com/
>>
>> On Wed, Jun 8, 2011 at 13:19, Carlos G Mendioroz <tron_at_huapi.ba.ar>
>> wrote:
>>> Why is that you won't see retransmissions if it is not TCP ?
>>> Try SIP over UDP, you will see retransmissions.
>>> NFS over UDP ? Same thing.
>>> Just because TCP is not in charge of them does not mean they will not
>> take
>>> place :)
>>> -Carlos
>>>
>>> Marko Milivojevic @ 8/6/2011 15:34 -0300 dixit:
>>>>
>>>> Is the application TCP? If it isn't, you won't see the retransmissions.
>>>>
>>>> And yeah - traffic is very likely being dropped by the switch, but
>>>> lacking any command output, it's hard to say for sure :-)
>>>>
>>>> --
>>>> Marko Milivojevic - CCIE #18427
>>>> Senior Technical Instructor - IPexpert
>>>>
>>>> FREE CCIE training: http://bit.ly/vLecture
>>>>
>>>> Mailto: markom_at_ipexpert.com
>>>> Telephone: +1.810.326.1444
>>>> Web: http://www.ipexpert.com/
>>>>
>>>> On Wed, Jun 8, 2011 at 08:32, Bernard Steven <buny.steven_at_gmail.com>
>>>> wrote:
>>>>>
>>>>> What will happen if a server sends a jumbo frame to the connected
>> switch
>>>>> that does not support (not configured) Jumbo frames ?
>>>>>
>>>>> My problem is when i capture traffic from server IF (tcpdump ) , i see
>>>>> large
>>>>> frames (1518<) , in the mean time , switch is not configured for JF and
>>>>> also
>>>>> i don't see any retransmissions in tcpdump. (assuming switch discards
>> the
>>>>> jumbo frame). And also i dont have any visibility on the other end of
>> the
>>>>> communication. Some how , application does not work.Switch is a 4948.
>>>>>
>>>>>
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>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>> --
>>> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina
>
>
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Received on Wed Jun 08 2011 - 21:28:35 ART