Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!SALT.ACC.COM!gary
From: gary@SALT.ACC.COM (Gary Krall)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: bridges & address filtering
Message-ID: <8906090324.AA20494@SALT.ACC.COM>
Date: 9 Jun 89 03:24:14 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 80

>Date: 31 May 89 22:43:45 GMT
>From: robert@g.ms.uky.edu  (Robert Lee)
>Organization: U of Kentucky, Communications Services, Networking.
>Subject: Re: bridges & address filtering
>To: tcp-ip@sri-nic.arpa
>Status: R

Robert,

>With the UB DLB we can program filters bi-directionally but not 
>uni-directionally.  It would be nice if we could do this with a bridge
>also it would be *very* nice if there was a extensive set of tools that
>would work with bridges at the network management level. 

ACC's ACS 4110 (remote ethernet bridge) product implements SNMP 
management in an effort to provide some of the tools necessary to
manage bridges.  

Currently, SNMP commands are entered locally through a RS232 console
port mounted on the rear of the unit.  Through that port commands
can be issued to the local unit or to any currently accessible
remote unit.  Management stations which support SNMP (and those
ACC enterprise specific variables) could also access the units.

>For example here are some things I would like to be able to do with
>a bridge.

>1) Be able to tell the bridge to disconnect from a ethernet for a time
>or until I tell it to turn its packet forwarding back on.

The SNMP implementation on the ACS 4110 unit supports the ability
to disconnect or connect from a ethernet in two ways.  The first is
to disable the physical port, or alternatively the spanning tree
port (802.1) may be disabled.  In either case when the port is
enabled packet forwarding may resume.

>2) Be able to tell the bridge to forward all the packets it sees.

In a local environment this might make sense, but in a remote
environment where bandwitdh is at a premium this is not suggested.
However, the ACS 4110 can certainly be configured to disable
"learning mode" and effectively forward all packets it sees.

>3) Programmable filters that don't degrade packet forwarding 
>to any high degree.

The ACS 4110 supports filters based on the 802.1 specification;
in general the specification of arbitrary filters is not
without it's cost.  It all comes down to implementation and
capabilities of the unit.

>4) A extensive set of statistical variables.  Like # packets/sec. 
>Collision etc etc.  Also it would be nice if these results 
>could be put into a file that can be processed with statistical 
>programs like SAS or SPSS.

SNMP management supports basic data collection and control.  Some 
statistics are available to the user such as number of packets passing
through an interface.  Rather then having the unit itself calculate
statistics, a SNMP based management station could
calculate more complex statistics such as packets/sec based on
collected data and so on.

>5) Bridges usually only look at the ethernet address header and
>not what type of packet it is.  It would be nice if there was a 
>facility that allow the bridge to forward based on packet types.  
>I can do this to some extent with filters now.

I mention this above, but in addition to priority forwarding on 
protocol type the ACS 4110 can also discard by protocol.

>Anyway, that's what I would like for a bridge.   

Hope that helped.

>Robert Lee
>SYSBOB@UKCC
>University of Kentucky

Gary.