[asterisk-users] network design philosophy and practice

[Jerry Jones]

>
> I can think of two valid reasons to physically segregate the networks:
>
> 1) Insurance. I.e., to eliminate the possibility that otherwise  
> properly configured QoS mechanisms become broken, either by  
> accident, incompetence, or badly-designed or rogue software or  
> hardware - or are otherwise handled carelessly as Jerry Jones  
> suggested. But this is not a compelling argument to me in any but  
> the most critical scenarios such as public-safety applications, etc.
>
or you wish to eliminate service runs - that is unless they are always  
billable and your customers do not mind you informing them they messed  
up again and that is why they ahd issues. This is ok once or twice but  
some customers just cant control things and IF possible to reduce  
areas where problems could arise why not.

> 2) Customer preference. If you need the business, then the customer  
> is always right. You might not have adequate credibility with the  
> customer or influence over the design decision, and if a customer in  
> such a situation gets it in their heads that voice and data can't  
> coexist on wires, then it can't.

True - just refer to my earlier examples. it is definately smarter at  
times to walk away.
>
>
> There is a variety of opinions, but no general consensus about where  
> QoS failures typically occur, when they occur.
>
> I'm wondering if anyone has anyone has ever experienced QoS issues  
> caused by contemporary Polycom phones like IP330s that had  
> workstations hanging off their builtin switches? If you did, were  
> you able to identify the cause, and was it due to any inherent  
> failure of the phone, such as not marking packets or prioritizing  
> dispatch correctly?

No. Well other than the port going dead or flaky. But the switch had  
best be up to the task. I find in installs where customer is looking  
for inexpensive phones, they tend to want very inexpensive - and  
normally unmanaged switches. I will not install an unmanaged switch  
for other than a residential install.

Plus even in fairly large installs where they are hitting an ITSP and  
traversing say a Watchguard firewall, the firewall will honor marked  
packets but cannot itself run diffserv and apply a tag. In this case  
the users pc's are in total control and all that corporate data and  
voip gets to compete with users streaming music et al to their desktops.

In this case unless there is a local voip server even their inside  
calls will suffer. But the proper solution is to always have a  
firewall/router than can properly dispatch the packets to the WAN.  
Have a couple Juniper firewalls I hope to try in a couple weeks to see  
how they perform.