[SANOG] MTU and MSS

Sat Aug 3 06:52:06 UTC 2013

yes, i have experienced it if there is a mismatch between POS/SDH interface
connecting to router Ethernet.

IMTIAZ AHMED
*T.E.D.S.* (Private) Limited.
273-B, St.55, F-11/4, Islamabad-44000.
T: +92 512 211 700 ,  M: +92 334 516 76 09 E: ceo at teds.pk <info at teds.pk>

On Sat, Aug 3, 2013 at 10:33 AM, Simon Sohel Baroi / IIG-ITC / Sr.Manager /
01678618243 / <simon.baroi at fiberathome.net> wrote:

> Hey Guys,
>
> Thanks for the extensive information.
>
> Imtiaz Vai, I'm connected with Bharti Airtel LONDON via MUX and with
> Ethernet connectivity. But there they proposed 9000 MTU. But with others
> via POS port we are connected with 4470 MTU. So my upstreams are in
> different MTU.
>
> Does it make any issue for INTERNET browsing experience.
>
> - SIMON.
> Fiber at Home.
>
>
>
>
>
>
> On Sat, Aug 3, 2013 at 6:26 AM, Imtiaz Ahmad <ceo at teds.pk> wrote:
>
>> Hi,
>>
>> May I add one more aspect, that is, SDH/DWDM transmission using Ethernet
>> encapsulation. Sometimes service degradation happens due to mismatch of MTU
>> size on Router interface and Tx interface and they always prefer jumbo
>> frames rather MTU 1500 bytes tradition.
>>
>> Regards
>>
>>
>> On Saturday, August 3, 2013, Joe Abley wrote:
>>
>>>  Hi Simon,
>>>
>>> MTU is an IP-later interface parameter which indicates the largest
>>> datagram that can be transmitted without fragmentation. The minimum for
>>> IPv4 is 576 bytes; the minimum for IPv6 is 1280 bytes.
>>>
>>> 1500 is a common default value; it corresponds to the largest frame
>>> (without support for jumbograms, 802.1q or other link-layer encaps)
>>> accepted on 100M Ethernet.
>>>
>>> Many systems will allow the MTU to be adjusted between the IP-specified
>>> minimum and the maximum allowed by the link layer being used.
>>>
>>> MSS is a TCP parameter. It denotes the largest datagram size
>>> (pre-fragmentation) used to transmit a TCP segment.
>>>
>>> If you know that your path commonly includes a link with an MTU lower
>>> than that seen directly by clients, e.g. a 1480 byte MTU on a PPPoE link to
>>> the Internet from a gateway router, you can decide to lower the MSS on
>>> clients behind the gateway to avoid fragmentation at the gateway. Sometimes
>>> this is done on the gateway as a pragmatic (if layer-violating) measure.
>>>
>>> Fragmentation happens differently in v4 than it does in v6. Both have
>>> their problems. Fragmentation in general is known to cause performance
>>> problems in the real world, and there are often advantages in taking steps
>>> to avoid it.
>>>
>>>
>>> Joe
>>>
>>> Aue Te Ariki! He toki ki roto taku mahuna!
>>>
>>> On 2013-08-02, at 16:43, "Simon Sohel Baroi / IIG-ITC / Sr.Manager /
>>> 01678618243 /" <simon.baroi at fiberathome.net> wrote:
>>>
>>> Hi All,
>>>
>>> Can any one help me to understand about MTU and MSS.
>>>
>>> What should be the best value for MTU ?
>>>
>>>  In my router interface I found its 1500, if I increase it or decrease
>>> it, does it put any effect to the CPU ?
>>>
>>> Does increasing MTU size help me for better browsing experience ? like
>>> Youtube.
>>>
>>> I'm using these routers as an Internet Gateway.
>>>
>>> - with regards
>>>
>>> SIMON.
>>> --
>>> *Simon Sohel Baroi  *|  Sr. Manager, Technology  |  PICO  |   ITC - IIG
>>>  |
>>> Cell : +880-1678-618243, +880-181-7022207  |  Desk : +880-9666776677
>>> Ext-1031  |
>>> Mail : simon.baroi at pico.net.bd  |  Skype : tx.fttx  |
>>>
>>> *
>>> Reduce. Reuse. Recycle. Respect. It's the little things that really can
>>> make a difference.
>>> *
>>>
>>> _______________________________________________
>>> sanog mailing list
>>> sanog at sanog.org
>>> https://lists.sanog.org/mailman/listinfo/sanog
>>>
>>>
>>
>> --
>> IMTIAZ AHMED
>> *T.E.D.S.* (Private) Limited.
>> 273-B, St.55, F-11/4, Islamabad-44000.
>> T: +92 512 211 700 ,  M: +92 334 516 76 09 E: ceo at teds.pk <info at teds.pk>
>>
>>
>> --
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>
>
>
> --
> *Simon Sohel Baroi  *|  Sr. Manager, Technology  |  PICO  |   ITC - IIG  |
> Cell : +880-1678-618243, +880-181-7022207  |  Desk : +880-9666776677
> Ext-1031  |
> Mail : simon.baroi at pico.net.bd <simon.baroi at fiberathome.net>  |  Skype :
> tx.fttx  |
>
> *
> Reduce. Reuse. Recycle. Respect. It's the little things that really can
> make a difference.
> *
>
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