Conference 7.286::fddi

As usual, the answer is: "See Raj Jain's 'FDDI Handbook'".

In this case, he has several chapters worth of material.  Chapters 22-24
address performance; chapter 25 covers error analysis, a related topic.

	paul

> As usual, the answer is: "See Raj Jain's 'FDDI Handbook'".

I see.  It seems like a magic book.  I'll poll localy to see if someone has it.

_Tak

I'd recommend getting your own.  Anyone who does a significant amount of
work with FDDI should have a copy.

ISBN 0-201-56376-2, Addison-Wesley, 1994.

	paul

    re: .2  Tak,
      Naoki Ido has Raj Jain's book (I sent it to him myself!).
    
    Debbie
    

I posted two notes(replies) to the HUB_MGNT notes file as follows.
If you have any advice or hints, please reply to the HUB notes.

Thanks,
_Tak

            <<< NETCAD::KALI$USER3:[NOTES$LIBRARY]HUB_MGNT.NOTE;1 >>>
                   -< DEChub/HUBwatch/PROBEwatch CONFERENCE >-
================================================================================
Note 638.9             HUBwatch can see FDDI utilization?                9 of 10
TKTVFS::NEMOTO "no facts, only interpretations"      24 lines   5-SEP-1994 09:23
                                   -< FCIS? >-
--------------------------------------------------------------------------------

Re: .-1

ELAN MIB 2.9 has it..  We are now sampling traffic data from Bridge900 as
a trial.

One question.  The RingLatency uses a void frame according to the MIB below.  
What void frames do you use to measure the latency while having Ring Purger 
off?

_Tak
 
    eMACRingLatency OBJECT-TYPE
        SYNTAX  INTEGER
        ACCESS  read-only
        STATUS  mandatory
        DESCRIPTION
               "The total ring latency in 1 nanosecond units, as measured
               by the amount of time that it takes to receive back a void
               frame transmitted by the MAC chip.  Note that implementations
               that do not have the capability to measure the ring latency
               will not return this object."
        ::= { efddiMACEntry 22 }

================================================================================
Note 638.10            HUBwatch can see FDDI utilization?               10 of 10
TKTVFS::NEMOTO "no facts, only interpretations"      29 lines   7-SEP-1994 11:22
--------------------------------------------------------------------------------

Follow-up questions -

1.  RingLatency data measured by MCC shows some drift.  When graphed, it 
    looks as if there are three horizontal bars: centered at ~17.050us, 
    drifted +/- ~.100us from the center.   
    Data is taken every 10minutes that makes 10minutes average.  The ring 
    in question has two DECnis and two DEChub900s.  

    Can this drift happen on rings?  Or something wrong with the
    measurement?  -- The ring purger is being disabled (so have been told).

2.  There is a topic in the FDDI notes (UPSAR::FDDI, 1186.*).
    My interpretation of the topic is that SNMP counters of the concentrator 
    only reflect the traffic to that concentrator (addressed to it:
    ie, SNMP packets, ping traffic to it). Other traffic that's just
    passing thorough is not counted. 

    Has Concentrator900 the same behaviour? -- when graphed interface 
    counter (in/out), it shows ~5% at some peaks and close up to ~2% on 
    average.  I wonder if SNMP or ping communication can make the traffic 
    that high.

It is our first experience to approach FDDI utilization and throughput
measurments.  We want to know if our observation is what we should see.
Any advice or hints would be very much appreciated.
  
Thanks,
_Tak 

The MAC uses a single form of void frame for all the things it needs it for:
ring purger, bridge strip, and latency measurement.  As I recall, the 
measurement is actually done by turning on bridge strip mode (temporarily,
I believe).

It makes perfect sense that you would see measurements that differ by
0.1 microsecond, since the measurement is done against the byte clock
(80 ns clock period).  So you get the normal +/- 1 quantization noise.

	paul

	1st answer:  Bridge Strip Mode uses VOID frames.  These are also used to measure ring latency
                     (or VOID frames from the Ring Purger).

	Drift: I don't know about the drift...but it seems real small (0.6%).  I wouldn't worry too much...

	Counters: 'if' counters only measure frames sent to the concentrator.  fddimibMACFrameCount count
                  everything (including voids...which makes it not very useful).

	Luc