| Title: | FDDI - The Next Generation |
| Moderator: | NETCAD::STEFANI |
| Created: | Thu Apr 27 1989 |
| Last Modified: | Thu Jun 05 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2259 |
| Total number of notes: | 8590 |
In calculating the 100/200 KM fiber length of an FDDI network, what
all fiber segments must be taken into account? Does this only include
the dual ring or must the fiber segments in a tree off the ring also
be considered? How are tree'd segment length's handled?
I have read through most of the FDDI Primer and some misc. tech.
papers. I just got a copy of Raj Jain's FDDI Handbook. However,
if someone could give me an overview of these questions, until I
have a chance to read Mr. Jain's book I'd appreciate it.
Thanks,
Richard
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 1835.1 | Sum all the paths | STEVMS::PETTENGILL | mulp | Tue Oct 17 1995 21:40 | 17 |
The only reason for the limit is to bound the token time so that its possible to decide if there is a problem. So this means the the worst case path length must not exceed 200 km or else it is possible that certain timers might expire. If you can ensure that the speed of light is faster than than the assumed worst case, you can make a larger ring. However, you should be taking into account the fact that such a large ring will not be able to operate with high utilization and will not be very responsive in a point to point configuration. You should really consider using GIGAswitch/FDDI's to limit the size of any FDDI ring and should have all the long segments be connected to a pair of GIGAswitch's so that the link will operate in full duplex mode and not have any token related latency. (Rule of thumb: 5ns per meter, so 200 km means 1,000,000 ns or 1 ms.) | |||||
| 1835.2 | Yes count SAS connections | CHOWDA::FAHEY | Are we having 'FUN' yet? | Mon Oct 23 1995 13:15 | 4 |
You must also count 2x lenght of the SAS devices. The token goes from
the concentrator to the device and back to the concentrator.
Jim
| |||||
| 1835.3 | Thanks for the info! | SWANDC::MAUTZ | Networks >= to DECnet | Fri Oct 27 1995 11:22 | 1 |
Thanks, that helps! | |||||