Conference 7.286::fddi

1346.0. "Multimedia on FDDI" by WOTVAX::PARRIS () Fri May 27 1994 06:22

I'm involved in an RFI response which includes a future requirement 
for multimedia - "isochronus data streams such as desktop video 
conferencing, multi-user whiteboard sessions etc".

As the initial backbone traffic is low, many segments all within one 
building containing both users and server, our initial response was a 
single FDDI with DECbridge 900MXs, introducing FDDI Personal Ethernet 
Modules for future multimedia users with the introduction of a 
GIGAswitch or possible migration to ATM when backbone traffic 
dictates.

This has brought back two questions:-

1 "How does this provide predictable latency over the backbone as 
required by multimedia users?"

2 "In the fully switched backbone, although point to point FDDI is 
utilised between hubs, and the GIGAswitch, the fact that each hub is 
the aggregation point for a number of users, each with a different 
traffic profile, and therefore providing varying frame sizes onto the 
FDDI backbone, could introduce jitter to users who need isochronus 
data, is this correct?"

My potential answer to 1 is that due to the low FDDI traffic levels 
the latency will be acceptable when compared to other causes, eg the 
PC.

However I'm struggling with 2 and any help would be gratefully 
accepted especially pro-FDDI rather than anti-ATM.

Many thanks in advance