Subject: Re: Traffic generated by fax over IP

From: Michael Spann <[email-masked]>
Date: Thu, 22 Oct 1998 18:23:25 -0700 (PDT)

On Fri, 24 Jul 1998 [email-masked] wrote:

> Hello Friends,
> 
> I am a graduate student at MIT, presently engaged in research on the
> impact on traffic over the Internet backbone, with more and more fax 
> projected to be sent over IP in the next 5 years.
> 
> Could you possibly enlighten me on how much internet traffic the
> following typical types of fax messages (sent over IP) would generate:
> 1. a "typical" two-page text fax.
> 2. a "typical" three-page fax with some drawings/graphs.
> 
> I look forward to your responses.
> 
> Thanks,
> Mahesh
> 

Real world data is hard to get.  A 'first order' approximation can be obtained
using ITU standard test images and making a number of assumptions.

If you assume that ITU test chart #1 is a 'typical' fax, and you assume that
the fax messages are using the current IFAX recommendation (i.e. simple mode)
and you assume that you are using mime64 encoding of the binary body part and
you assume that the mail header is no bigger than the ones I see on this
mailing list, you get the following:

. A mail header is about 1300 bytes.

. ITU test chart #1 is about 35000 bytes with MH compression and a TIFF
header (TIFF profile S)

. mime64 encoding increases this by a factor of 8/6 unless you have 8bit
transparent throughout the net.

thus, your two page 'typical' fax will generate about a 93k mail message.

Interestingly, business grade faxes are not significanly larger than the ITU
test images.  Also remember, this is for simple mode IFAX.  EIFAX adds support
for additional TIFF profiles.  TIFF profile F will reduce the size of the mail
message noticably and TIFF profile J will reduce the size of the mail message
a LOT.