Gigabit Switch

Bogdan Costescu bogdan.costescu at iwr.uni-heidelberg.de
Tue Nov 11 15:27:48 EST 2003


On Tue, 11 Nov 2003, Mark Hahn wrote:

> 1. suppose you could attach a QOS/TOS tag to small packets, and 
> have the switch give them preferential treatment.  for instance,
> if there's a congested port with a backlog, let small packets 
> "cut" the queue.

That means that you actually have a backlog. Many switches, especially the 
cheap ones, have small buffers that can be filled fast, so further (small) 
packets might not make it to the switch at all.
Furthermore, by letting packets go out-of-order, you make life harder for 
the receiver...

> 2. the vendor claims that multicast is reliable. 

See Donald's answers to this very question in this thread:

http://marc.theaimsgroup.com/?l=linux-net&m=106665132425192&w=2

> 3. it would be neat to be able to query performance/load/queueing stats
> from the switch on a per-port basis.

That is actually one of the 2 things that I use out of a managed switch... 
Althought I think the information should be available as SNMP, I use it 
only when I try to find out if there is some networking problem, which is 
rarely enough, so I always used the switch CLI or web interface to do it.

The second thing that I use from a managed switch is VLAN - not for 
splitting it in half for bonding, but for things like separating the the 
control/login/NFS connection from the one used for parallel computation 
(in case of at least 2 NICs/node).

-- 
Bogdan Costescu

IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu at IWR.Uni-Heidelberg.De



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