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New Member

T.37 FAX from router limits

The router to Unity T.37 FAX service is billed as, “The Cisco Unity IP Fax toll is intended for simple, small, low-traffic fax environments.” Having said that, are there any safe guidelines on the number of FAXes it will handle for incoming use only? Would the load on the Unity Server or on the router be the limiting factor? We are looking at a MCS 7845 and a Cisco 3825 router. I want to set some expectations and I don’t want what the users consider “light” to overload the server or router.

Again, this is for incoming only. Unity 4.1.

5 REPLIES
Cisco Employee

Re: T.37 FAX from router limits

Incoming is no problem at all - this is a basic routing function which is not much load on the system at all, at least from the Unity side of the fence.

Outbound is much heavier because all the rendering into a single TIF required by the gateway is done on the Unity server itself using print drivers for the application(s) assigned to the attachment document types (i.e. DOC, TXT, BMP etc...) - this can seriously tax the processor and must be done liniearly which can cause a bottleneck if there's a burst of outbound faxing.

So if you're on doing incoming, from the Unity perspective there's no issue.

Cisco Employee

Re: T.37 FAX from router limits

For inbound faxing, the router does most of the work since it has to negotiate with the fax machine, save the fax in a TIF format and then email it to the unity fax box. It's still hard to quantify and I would--under any circumstances--recommend putting as much memory as possible in that router. Certainly a few faxes at a time shouldn't be a problem. If you're talking about a full T1 pummeling the box with faxes, it probably won't be able to keep up. So much depends on what else is going on; i.e. concurrent voice calls, big routing tables, etc.

New Member

Re: T.37 FAX from router limits

Thanks for the input. It is most helpful!

So if I tell them two or four simultaneous FAXes the 3825 shouldn't be overloaded?

I'll goose up the memory.

Re: T.37 FAX from router limits

I guess its best to dedicate a router with a PRI just for fax calls (if cost can be justified and you have a good volume of calls).

Are there any white papers that talk about how much memory / cpu power is utilized for onramp/offramp fax gateway to work with Unity server.?

Cisco Employee

Re: T.37 FAX from router limits

There's a minimum requirements list here:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t11/faxapp/t37.htm#wp1039411

However, I can tell you that the biggest bottleneck for T37 is memory. Whichever platform you choose, I would definitely max out the memory.

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