To Nagle or not to Nagle

[paulmacdonald]

I'm going to be sourcing my MOH files on remote routers at some of our sites. My understanding is that the "Service Nagle" can cause problems in this circumstance. Since the files usually go out over UDP, what is the reason?

[bwalchez]

When Cisco gateways are working with Cisco CallManager or third-party endpoints that do not support fastStart and initiate the H.323 slowstart procedures after the user answers the call, there could be a perceptible delay in the media. Problems can include:

Cut-through on slow WAN links.

Round trip latency in the IP network between the gateway and terminating DTE.

Delayed audio cutover.

Workaround: If possible, use h323 fast start. If 12.2(2)XA4 or 12.2XB3 images are used, enable the following hidden command.

#conf t

#voice service voip

#h323

#no tcp options delay

This turns off the Nagle algorithm for H.323 TCP connections and thus reduces the delay.