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> I've seen Chipcom ifInDiscards shooting through the roof. I understand
> what the discards "are", but what kind of problem might this be
> indicating?
> I guess I'm just gonna be one of those guys who has to have it all
> spelled out.
Hi -Dan,
My first admission is that I have not worked in the realm of IP. Therefore the
*opinions* given are based on DECnet experience and may or may not apply, you
be the judge :-).
The dropping of packets is usually a resource problem either with a router
or bandwidth. If you were dropping packets 'outbound' it could be your circuit
is saturated and can't handle the packet in a proper timeframe, given the
number of buffers it has to work with. If you run out of buffers for transit
packets before you can transmit then they get 'discarded'. Outbound loss can
also be attributed to transmission 'delay' with comparison to the packet
acknowledgement schema used at the data link layer (that's a lengthy discussion
and doesn't seem to apply so I'll skip it).
Your situation of inbound losses would point me in the direction of the local
router's inability to transfer the loads of packets it is given. Again, it
could be a situation where the router can't get the packet transmitted before
its buffers fill then overrun (discarding the packets). Some questions to ask
yourself (and the MCC station). What is the packet rate of the router and what
does the vendor supposedly support? Do you have buffer or other errors at the
system level? If you offload a circuit (and its packet thruput) to another
router does the problem disapppear. What is adjustable on the router: buffer
counts, window sizes, etc...? Run MCC PA commands at somewhat short intervals
for both routers and each interface on either end. This may give some light.
4 simutaneous commands:
Show SNMP router_a all statistics, at every minute etc...
Show SNMP router_b all statistics, at every minute etc...
Show SNMP router_a inter 1 all statistics, at every minute etc...
Show SNMP router_b inter 2 all statistics, at every minute etc...
advanced practical mcc uses 303 (6 credits)
regards,
brad...
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| Brad,
Your ideas are on track for routers, but what about HUBs? I need to do
some more research here in my "spare" time (between 11pm and 1am).
I am beginning to suspect certain hardware components, specifically ODS
fiber optic modems (ODS234, ODS236, ...), as well as Chipcom and
Cabletron hubs and Fiber Optic Transceivers, when they are in certain
mixed configurations.
I need some enhancements to DECmcc statistics to be able to do this
more easily. What I really need is a modification to alarms to allow
me to be able to alarm on a DELTA between polls (hint, hint).
Our cluster is LAVC, 19 nodes, 15 of which are on a single Cabletron
HUB, the other 4 on Thickwire Ethernet. Our collision rates are
excessive. So are dropped packets, receive and send failures.
The Chipcom hub to which I referred earlier has several VAXes and Suns
on it. ifOutDiscards are 0. ifInDiscards are excessive. I just need
to get some more info on what this symptom indicates.
By the way, before this course is over, I suspect it will be
graduate-level (500+). ;^)
-Dan
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