[Asterisk-Users] Snom firmwares suck <--additional datapoint to consider

[Rich Adamson]

Dr. Michael J. Chudobiak wrote:
>> I looked long and hard at the LAN and it was basically narrowed down 
>> to the
>> switches. In this smaller install, several cheapo Dlink ($30) switches
>> de-aggregate a Cisco Catalyst switch. What I noticed was that any phone
>> plugged direcly into the Catalyst did *not* lock up or reboot. Any phone
>> plugged into the crap switches experienced the lockup. So now we are 
>> down to
>> the cheap switches themselves. We are nuking the Dlink switches and
>> replacing them with 3com workgroup switches, same as what we use in the
>> large install to good effect, and I fully expect the problem to 
>> dissapear. 
> 
> So does anyone have any theories as to what the technical difference 
> between a "good" switch and a "bad" or "cheapo" switch actually is? 
> Lower latency? Better grounding? More cowbell?

By far, the majority of switches on the market today will work just fine 
for VoIP. Past professional experience dictates (in my mind) that a 
"managed" switch is the only reasonable approach for any network larger 
then a home office.

There are some inexpensive switches being sold that are less then 
adequate for business use. For example, Dell rebranded and sold some 
switches about two years ago that would reboot if an html packet hit the 
manager IP address; didn't even have to be a crafted packet. Cabletron 
sold a number of models that would auto reboot at random intervals. HP 
had some issues with early firmware that essentially resulted in reboots 
(it was fixed in later firmware versions).

Our company conducts professional network performance, security, and 
voip readniness assessments, and have worked with corporations and 
institutions in over 40 US states in the last 12 years. We constantly 
see folks making assumptions about how switches function that are far 
less then accurate.  One example is leaving switch ports to auto 
negotiate duplex settings. Roughly 50% of the time the switch (and/or 
device attached to the switch) will get it wrong; one will be full 
duplex while the other ends up half duplex. "That" one item will have a 
serious impact on voip quality.

The only way to ensure a solid network infrastructure is to use switches 
that are "manageable", and there are now lots of inexpensive switches on 
the market that are manageable. In "very" general terms, the higher the 
cost of the switch, the more functionality one receives.

Also in very general terms, the larger the network, the more 
functionality one needs within the switches. In other words, a network 
with several hundred switch ports likely requires switches with the 
capability of supporting vlans, packet queuing/prioritization, etc. 
Small networks (eg, low traffic volumes) in most cases do not need those 
same functions.

So, your choice of switches is highly dependent on the size of network 
that your working with.