[cisco-voip] Tftp bandwidth Requirements question

[Ryan Ratliff]

It depends on the phone model and the specific phone load.  The newer  
phones (79x1 and later and 7970) have phone loads that have grown to  
several Mb, and will probably only get bigger.  The peer firmware  
sharing feature was introduced with the 8.3 loads to help phones in  
remote sites upgrade phone loads faster.

Most of the time it's delay rather than bandwidth that causes issues  
with TFTP.  Since each data packet has to be Ack'd at the application  
layer by the phone before the next one can be sent a high latency  
between phone and server can cause very large upgrade times.

If you need to check on exactly how much data a phone gets from the  
TFTP server for the config file, phone load, etc I'd encourage you to  
get a phone and a packet sniffer and go to town.  You can get the zip  
file for a given phone load from cisco.com to see how big the files  
are that the phone will be downloading.

HTH,

-Ryan

On May 15, 2008, at 10:29 AM, Jordi Riba (Europe) wrote:

Hi,

I've been reading about bandwidth requirements for a Multisite WAN  
with Centralized Call Processing IPT deployment model and I have not  
found information about TFTP bandwidth requirements.

I know that tftp packets are marked by CCM with DSCP 26 as all other  
signalling packets. Then what I don't understand is if I configure  
for a 120 IP phones branch office deployment a Signalling CoS  
(between headquarters and branch office) of around 62Kbps... It will  
take a very long time to register all phones if they need to download  
their firmware from CCM, isn't it?

Do you know how big is the total amount of data that a phone  
downloads from CCM the first time it start? where can I check it?

Do you know how big is the total amout of data a phone need to  
download from CCM when it registers again to CCM after an SRST  
situation?

All help will be very appreciated.

Thanks!

Jordi!


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