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New Member

Unified Bandwidth Requirements

Hello, <br>We're currently running Unity 2.4.161 VM only and Call Manager 3.13a in a centralized call processing environment.<br>Our Call Manager's and Unity are located at our central site, and we have users from second site connected via a full T1. We've just completed our migration to Ex2k and have a Exchange 2000 server in each site, configured in seperate routing groups.<br>We are planning our migration to Unified messaging, and have noticed that Unity 3 will only support a single routing group. We could consolidate our servers into a single routing group but I'm unclear what the bandwidth impact of streaming voicemail across the WAN would be. We have good QoS and regularly support as many as 10 G7.11 VOIP calls across the WAN, but I'm guessing that traffic between the Exchange Server and Unity would be data and not VOIP. <br>Any suggestions?<br><br>Walter Williams<br>IS Manager<br>Graphics Microsystems Inc.<br><br>


Re: Unified Bandwidth Requirements

There is no hard and fast you need "X" mbs for "Y" users in your voice mail system that I can give you here but generally the only reason to use routing groups is for connecting Exchange servers across lower bandwidth connections which is why we don't support a single Unity server crossing routing group boundaries. I'm curious why you needed seperate routing groups if the bandwidth between them is high.

Unity is streaming messages directly out of Exchnage when playing back via the phone, of course, and into exchange when subscribers are leaving messages for other subscribers. This is done directly to the respective home store so if the bandwidth to the Exchange server that houses the subscriber in question is low, you're going to have trouble. We're also monitoring the inboxes on the respective Exchange servers for notification events (MWI and pagers etc...) which can add some overhead but not a huge amount. Of course when you call in and log in over the phone we run a filter on your inbox to get your message count. We also "ping" each Exchange server periodically to make sure it's up and alive so we don't try to attach to it and stream messages when it's down (MAPI timeouts are horrible when you do this and it's off line).

Short story, most of your bandwidth is taken up with streaming messages in/out of the mailstores in Exchange store but that's not the full story. You can reasonably easily estimate the amount of bandwidth needed for streaming messages stored in G711 or G729a and multiplying by the number of users who could be checking messages at the same time over the phone, nothing overly complicated there but it's hard to give you a firm number in a formula you can just chunk through to get the bandwidth reccomendation as a whole. The solutions group is working on a big, detailed white paper that will help folks figure out what they should really need in the way of bandwidth that'll hopefully be published in a couple months.

Jeff Lindborg
Unity Technical Lead/Answer Monkey
Cisco Systems (new page for Unity support tools and scripts)


Re: Unified Bandwidth Requirements

Thanks for your detailed response.

To answer your question (re:why seperate routing groups)
We just completed a migration from Exchange 5.5 which were configured as two sites. The decision to have two sites was made at a time when we had much less bandwidth.
I'm seriously considering consolidating the routing groups.

We only have 71 voice mail users spread across two sites, and we rarely use more than 4 ports at a time, so my gut says that we could get by with a single Unity server at our central site, but I wanted a sanity check from someone with more experience with unified.


Walter Williams
IS Manager
Graphics Microsystems Inc.

Walter Williams
IS Manager
Graphics Microsystems Inc.

New Member

Re: Unified Bandwidth Requirements

Hi Jeff,

I was directed to this post by TAC. We are deploying a Unity UM 3.1 solution, where we need to have Exchange 2000 server in a central location. Unity server will have access to the server over 10M ATM pipe. We have 12 port capacity for VM access and I am not sure that checking a VM over the phone, takes up a port out of this pool. I understand that it does. So maximum possible users accessing VM at one time would be no more than 12. We are using G711, so actual bandwidth we need to reserve ~12*106k=1.2M. Now when you said that VM are streamed to the phone user from Exchange, does it actually go through Unity or goes directly to phone. I would think through Unity, since users is actually using Unity to access VM. In this case I should plan on enabling QoS from voice traffic between Exchange and Unity? If not, then I should enable QoS for VM traffic from Exchange to IP Phones? Your advise would be highly appreciated.

Also you mentioned that solutions group is working on some white paper on this. Please send me the link if the paper is available.




Re: Unified Bandwidth Requirements

Which version of Exchange do you have? How many Exchange servers will Unity service and what is their location? Is Exchange on box? How many users will be on each Exchange server?



New Member

Re: Unified Bandwidth Requirements

Thanks for your response:

This is the info:

1. Exchange 2000

2. One Exchange server for now, may be two in future, off site from Unity location over 10M ATM pipe.

3. Using dedicated server for Exchange 2000.

4. No. of users will be about 250 on Exchange 2000



Re: Unified Bandwidth Requirements

The design you wish to implement isn't supported. The Partner Exchange Server must be in the same physical location as Unity. This URL has some data regarding this requirement:

We are in the process of writing a more complete guide to this type of configuration. These are the basic design principals:

-The Unity partner server must be on the same LAN as Unity (Server with the Unity_ mailbox)

-Unity can not have Exchange installed on box

-Exchange servers connected over a WAN link must not be the DC/DG which Unity is synchronizing with.

-40 ms of one-way delay is that maximum (80 round trip)

-All traffic between Unity and the remove Exchange server must be prioritized

These are the bandwidth requirements:

WAN Speed | Codec | LLQ Priority Queue (Voice) in Kbps | Number of Calls Call to Subscriber Ratio | Maximum # of Users | Maximum One-way WAN Delay

256K G711 109 1 1:25 25 40 ms

512K G711 219 2 1:25 50 40 ms

256K G729 109 4 1:25 100 40 ms

512K G729 219 8 1:25 200 40 ms

T1/1536K G711 657 8 1:25 200 40 ms

T1/1536K G729 657 25 1:25 625 40 ms