asterisk users - Oct 2008 - network design philosophy and practice

I'm wondering how prevalent the practice of physically segregating voice 
and data networks is in the Real World.

What are the factors that typically lead to such a decision?  
DIscussions of pros and cons are most welcome by me.

Experiences, anybody?


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On October 29, 2008 10:19:36 am Bill Michaelson wrote:
> I'm wondering how prevalent the practice of physically segregating
voice
> and data networks is in the Real World.
>
> What are the factors that typically lead to such a decision?
> DIscussions of pros and cons are most welcome by me.
>
> Experiences, anybody?
I'm a pragmatist; most offices have one network jack at each station; I run 
voice and data on the same physical wire, but if at all possible I try to 
split things off using smarter switches and VLANs.

-A.

On Oct 29, 2008, at 9:19 AM, Bill Michaelson wrote:
> I'm wondering how prevalent the practice of physically segregating  
> voice and data networks is in the Real World.
>
> What are the factors that typically lead to such a decision?   
> DIscussions of pros and cons are most welcome by me.
>
> Experiences, anybody?

In almost all cases it is much better to have two seperate networks.  
This may be impractical in some smaller installs, but in any office  
setting we always do this. The only reason I can think of not to is to  
eliminate the cost of the second cable. In the overall scheme though  
this is really a minimal cost compared to dealing with issues that may  
arise over having a fully integrated network. We also only install  
managed switches and do have seperate vlans. The vlans may be either  
port based or tagged.

In the last five years of doing VOIP installs, we have only had one  
customer the refused to add the second cable, and they were also the  
most unhappy. They also demanded the lowest cost phone option (IP301)  
and a Snom for an operator console. It all worked, just not very well,  
and ultimately they relaced it all.

I n the real world, there usually are very inexperienced people using  
and managing the network. What is trivial in the data side becomes  
critical on the voice side and since most networks are run by the data  
guys, having it as seperate as possible really helps keep it all  
working well. One of the not so obvious issues is when the data guys  
are having a problem and go around rebooting things, dropping phone  
calls. On this list we tend to only think about the voice side, just  
keep in mind any data operations which are also going on.

Bill Michaelson wrote:
> I'm wondering how prevalent the practice of physically segregating 
> voice and data networks is in the Real World.
>
> What are the factors that typically lead to such a decision?  
> DIscussions of pros and cons are most welcome by me.
>
> Experiences, anybody?
>
We chose to go with a segregated network and certainly don't regret the 
choice. Voice and data are on separate ports at the desk, avoiding QoS 
issues completely and reducing confision amongst users who still expect 
separate Phone and Computer plugs on the wall.
The traffic does run through the same switches and inter-switch trunks 
but always on distinct VLANs.

My experience with connecting the desktop computer through the phone has 
been very poor. Audio breaks up when the computer does large data transfers.

"Yes, Sir. I'll just look that up in our 
datab...ba....ba.....ba....sssss.....ssssss......ssssss......se"

In addition our users require gigabit to the desktop. The phones are 100Mb.

Worst part is the few Cisco phones we have insist on "searching for 
VLAN" (which doesn't exist) for 5 minutes on startup. Hopefully they 
will be replaced through attrition but despite being over-priced, 
over-featured and proprietary, Cisco do build robust kit. Sigh.....

regards,

Drew


-- 
Drew Gibson

Systems Administrator
OANDA Corporation
www.oanda.com

On Wed, 29 Oct 2008, Bill Michaelson wrote:
> I'm wondering how prevalent the practice of physically segregating
voice and
> data networks is in the Real World.
>
> What are the factors that typically lead to such a decision?  DIscussions
of
> pros and cons are most welcome by me.
Customer budget and choice...

I've installed in-line phones where there has been one drop point per 
desk, and installed a separate LAN for phones for a customer who wanted 
it. If I were dealing with anything less than a small office, or they 
needed Gb to the desktop, I'd get them to run a 2nd line for phones and 
put them on separate switches.

My biggest in-line client has 25 desks and were on a tight budget when 
they moved offices, so they have phones in-line with their PCs (diskless 
Linux workstations!) and we did some tests at install time and couldn't 
see any issues at the time (or hear any issues!) That was just over a year 
ago, and I was in-touch recently for an anual review and everything was 
going just fine for them.

Not had a pressing need to ever use VLANS (but I typically don't deal with 
clients who want/need that) but putting all the VoIP devices on one bank 
of switches and data on another works very well.

Gordon

Alex Balashov wrote:
> Send asterisk-users mailing list submissions to
> 	asterisk-users at lists.digium.com
> I'm pretty sure they meant two logical networks.  At least, I hope they
did.
>   
Unfortunately, I was indeed referring to two physical networks. Cabling, 
switches, everything, all the way back to the TDM connection to the
PSTN.
> David Gibbons wrote:
>
>   
>> Two separate networks? Did I miss something? I feel like I'm taking
crazy pills! Two separate physical networks means twice the hassle, twice the
maintenance, twice the cost, twice the headache. Not to mention the fact that
the whole idea of VOIP is to simplify IT and focus on converging data and voice
networks.
>>
>> This is what VLANs and QOS do best. I dare say it's what they were
designed foe. I can't think of any reason that I would ever recommend two
ports per desk to support telephony -- ever. It's ludicrous to think that
two ports will be better than one if we're setting up our VLANs and QOS
properly. A phone takes very, very little bandwidth away from the desktop and a
decent one will support tagging its frames for the alternate voice VLAN.
I agree, especially about QoS design intent. But I posted my question as 
a sanity check, and there seems to be no shortage of opinions. Now mine:

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.

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.

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?



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