At 02:40 PM 9/4/01, khramov wrote:
>I need to change frame size on of my Token Ring subnets. If I change the
>Token Ring frame size on the router and it will be different (larger)
>than the frame size that is configured on a work station how is it going
>to affect the work station? And if I change the frame size on the
>workstation first would that crash the router?
>Thanks
It shouldn't be a serious problem either way you do it. Users may have to
re-establish connections, however.
Are the routers truly routers or are they source-routing bridges? With
source-route bridging, each bridge checks the "largest frame" field and
decrements it if the bridge is configured for something smaller than is in
the frame. This happens during route discovery and session establishment.
Changing one of the bridges after sessions are established could cause
problems.
If the routers are truly routers and are routing IP, there's a similar
situation. IP hosts can use IP maximum transmission unit (MTU) discovery to
determine the largest possible frame size to use. This happens during
session establishment. Changing the MTU on one of the routers after
sessions are established could cause problems.
But routers shouldn't crash and there shouldn't be any other dire
consequences. Also, it sounds like you are increasing MTU which is less
worrisome than decreasing MTU.
Do you do any translational bridging between Ethernet and Token Ring
segments? Translational bridging can be difficult to get working,
especially if you use Token Ring frame sizes that are larger than Ethernet
allows (1500 bytes). If you use routing instead of bridging, there will be
fewer problems.
If your routers are now going to need to fragment and reassemble IP
packets, in order to go between Token Ring which supports larger frames and
Ethernet which supports 1500 byte frames, keep in mind that the routers
will be slower. This is additional work that they don't normally have to
do. I think it forces them to use process switching instead of the faster
switching methods.
Priscilla
________________________
Priscilla Oppenheimer
http://www.priscilla.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=18472&t=18466
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