Subject: [Isis-wg] Comments on < draft-ash-ospf-isis-congestion-control-00.txt >

From: Jeff Parker <[email-masked]>
Date: Thu, 16 Aug 2001 15:27:44 -0400

Jerry -
	I've been reading your draft <
draft-ash-ospf-isis-congestion-control-00.txt >
with interest.  Here are a few editorial comments.  I also have some
questions about your
scenarios in order to reproduce them here.  I think it would be good to have
a well
understood stress test that reflects an interesting test case, rather than
another
round of line-rate forwarding or connections per second test.  

> b)      how a node might control its workload once congestion is detected,
> such as through 
> *       the throttling of new connection setups, topology-status updates,
> and Hello updates with the use of automatic congestion control mechanisms,

1) Perhaps the title should mention PNNI: I'm not sure which connection
setups
   you would want to restrict in OSPF or ISIS.

2) I'm not sure that you really mean "throttling... Hello updates".  In your
   next paragraph, you advocate special handling of Hello Messages to assure
   they go through.  

>         * Inability to segment the network (into smaller "peer groups") to
aid
>          in the LS protocol recovery

I'm not sure what you are asking for here.  There is no obstacle in either
OSPF
or ISIS to create small peer groups.  In fact, your sample has very small
(4)
peer groups.  Do you want to reconfigure on the fly?  Do you want more
levels of 
hierarchy?

> 2.2 Vendor Analysis of Product Performance

> Various vendors and service providers were asked to analyze their product
> with reference to how their LS protocol recovers from a total network
> failure, that is, loss of all database information in the specified
> scenario.  The specification of the failure presented to the vendors made
> the following assumptions:

> 1.      400 node network is considered
> a)      100 backbone nodes
> b)      3 edge nodes per backbone node (Edge single homed)
> c)      Each backbone node is connected to no more than 10 nodes (maximum
> node adjacency is 13, which defines a sparse network)
> 1.      There are 101 areas
> a)      1 backbone area with 100 backbone nodes
> b)      100 edge areas, each with 3 nodes, all homed on the backbone peer
> group
> 1.      1,000,000 addresses are advertised in the network
> 2.      maximum node adjacency is 13
> a)      sparse network

I found the numbering confusing, and don't know if this is one specification
or three.  This might mean

        * 300 Edge Nodes

        * 100 Backbone nodes.
                - Each backbone node connects to 3 edge nodes
                - Each backbone node connects to 10 other backbone nodes
                - Each cluster of 3 edge nodes and backbone router forms a
single unique area
                - Each edge node advertises 3.333K routes

but other configurations are possible.  I would be interested to know how
your 
backbone routers are connected to each other. 
  
> During the study, a TSU
> storm of size X is created at instant of time 100 seconds where storm-size
> is defined as the number of TSUs generated during a storm.  Three cases
are
> considered with X = 300, 600 and 900 respectively.  

Can you clarify who originates these 300*X packets?  Is it the edge routers?
What are the sizes of the packets, and what are the contents?  For example,
I assume that you don't simply have two versions of each edge router's
topology
and send one then the other.  These details are probably in the paper
[choudhury] 
cited.  Is that paper publically available yet?

Perhaps you could define the test you describe in enough detail to provide
an interesting synthetic test of general utility.  I'm sure AT&T would love
to push back this test from your labs to your suppliers.  If the description
is clear cut enough, some of the test vendors might be able to produce
equipment
that could direct such a storm at a device under test.  May I be the first
to suggest the name "Link Adjacency Stability Test, G. Ash Switch Profiler",
or 
LAST GASP.  
 
- jeff parker
- axiowave networks
 
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