New Mitel 3300 network question 2

[jtphoneman]

Hello, I will try to explain this scenario the best I can. I am not sure if the deployment will work the way the customer has asked for. Thanks for the help..

A customer has 5 seperate networks, each network has its own HP managed L2 switch. Each L2 switch is connected back to a L3 switch for routing between subnets. This network has one DHCP server that provides different scopes for the different subnets, DHCP packts are relayed using a DHCP Relay agent in each L2 switch. The customer wants us to install a 3300 on this network and have the IP phones and PC's co-exist on the same subnet in which they are local to. We suggested implmenting Vlans to seperate the voice and data traffic but he insists on no Voice Vlan.

Would we be able to use the same DHCP server as the PC's but define option 150 so the phones would be able to communicate with the 3300? Would no L2 QoS be a major concern? Would this scenario even work?

Thanks

 

[tlpeter]

Insist Vlans!
Tell him that no Vlans can mean bad voice quality or broadcast storms in his network.


BAZINGA!

I'm not insane, my mother had me tested!

 

[bobcheese]

how big are the subnets? Will there be IP trunks between the controllers? Generaly VLAN's would be the norm.

 

[kwbMitel]

If the customer insists on no VLAN's fine.

You however must insist that he/she sign a document that all voice quality issues are not covered by any maintenance contract. Voice quality issues will be billed as time and materials at $XXX.XX /hr with no guarantee of resolution.

This has always got the point across rather quickly for me. I've only had one customer sign and they regretted it.

**********************************************
What's most important is that you realise ... There is no spoon.

 

[jtphoneman]

Thanks for the replies, their will be only one controller. I am checking with the customer now to find out the size of the subnets.

So will the Mitel Phones be able to get their DHCP informaitonand communicate with the COntroller if we use his DHCP Server & we put the correct options in?

 

[dryaquaman]

Using their DHCP server will usually work just fine - depending on what they're using. Assuming Windows.

But tacking onto this thread, hoping to get kwbMitel's input, how do you handle voice quality in an all softphone environment? UCA - latest version, 3300 latest version?

Dry Aquaman

http://www.university-music-on-hold.com

 

[jtphoneman]

Hey guys this customer will have roughly 30 devices per subnet. No more than that.
Thanks

 

[kwbMitel]

Number of phones is not the point. Exposing the phones to unnecessary data traffic without prioritization can be a problem for a single phone.

DryAquaman - I've never really had a site with more than 1 or 2 softphones. My understanding is that the application does prioritation and data shaping much like a Teleworker.


**********************************************
What's most important is that you realise ... There is no spoon.

 

[jtphoneman]

Okay, so it sounds like this scenario will work. Phones will be able to register and communicate with the 3300 okay. I just need to ask the customer to sign a document that states we will not gaurentee QoS.

When we mention QoS Customer states:

"If you are concerned about latency, we currently about 3 tents of a millisecond between edge switches and core switches, and we can also set packet priorities based on port number to further provide a better quality of services to the phones.
"

 

[kwbMitel]

Latency is only a small part of the equation.

If the customer is willing to take responsibility for Voice Quality issues. Let him.

It is entirely possible that everything will be fine and the Data/Voice will play nice.

Just make sure your ass is covered and that you can't be dragged down the rathole if problems occur.



**********************************************
What's most important is that you realise ... There is no spoon.

 

[tlpeter]

The problem is that you will never know which applications or equiptment screws up the voice packets.

Read this part (thanks to wikipedia)



When looking at packet-switched networks, quality of service is affected by various factors, which can be divided into “human” and “technical” factors. Human factors include: stability of service, availability of service, delays, user information. Technical factors include: reliability, scalability, effectiveness, maintainability, Grade of Service, etc.[3]

Many things can happen to packets as they travel from origin to destination, resulting in the following problems as seen from the point of view of the sender and receiver:
Low throughput
Due to varying load from other users sharing the same network resources, the bit rate (the maximum throughput) that can be provided to a certain data stream may be too low for realtime multimedia services if all data streams get the same scheduling priority.
Dropped packets
The routers might fail to deliver (drop) some packets if their data is corrupted or they arrive when their buffers are already full. The receiving application may ask for this information to be retransmitted, possibly causing severe delays in the overall transmission.
Errors
Sometimes packets are corrupted due to bit errors caused by noise and interference, especially in wireless communications and long copper wires. The receiver has to detect this and, just as if the packet was dropped, may ask for this information to be retransmitted.
Latency
It might take a long time for each packet to reach its destination, because it gets held up in long queues, or takes a less direct route to avoid congestion. This is different from throughput, as the delay can build up over time, even if the throughput is almost normal. In some cases, excessive latency can render an application such as VoIP or online gaming unusable.
Jitter
Packets from the source will reach the destination with different delays. A packet's delay varies with its position in the queues of the routers along the path between source and destination and this position can vary unpredictably. This variation in delay is known as jitter and can seriously affect the quality of streaming audio and/or video.
Out-of-order delivery
When a collection of related packets is routed through a network, different packets may take different routes, each resulting in a different delay. The result is that the packets arrive in a different order than they were sent. This problem requires special additional protocols responsible for rearranging out-of-order packets to an isochronous state once they reach their destination. This is especially important for video and VoIP streams where quality is dramatically affected by both latency and lack of sequence.

BAZINGA!

I'm not insane, my mother had me tested!

 

[kwbMitel]

tlpeter - Nice document.

This appears to be a case of leading a horse to water though.

Some customers simply can't be convinced (we all have one)

**********************************************
What's most important is that you realise ... There is no spoon.

 

[tlpeter]

I know, some should be kicked out and never come back
Just be save and they will come back to you to fix it but now payed instead of doing it at own costs.


BAZINGA!

I'm not insane, my mother had me tested!

 

[danramirez]

That customer has no idea of networking/switching. Make him to have Vlans!

I has happened to me a lot of times that ITs don't use Vlans simply because they don't know what they are for, and they don't understand how to use/configure them. Tagg Untagg may sound like chinese and they simply don't want to use them.

Again, use Vlans.

 

[jtphoneman]

Hey Guys, thanks for all the input. I have had a long talk with my manager. He told our sales dept. that we would not install this job unless the customer signs a document stating we are not responsible for voice quality. I was asked by the sales team and told them I did not recommend us doing this install without allowing proper network design utilizing a voice vlan.

I will post the outcome in a week or so....