Technical Library

Network Timers

There are a variety of timers in the GSM/GPRS, EDGE, and UMTS/HSDPA networks that affect IP addresses and IP networking. Many of these timers can be customized with a custom APN.

Timer	Function	Current Default Value
PDP Context	The amount of time before the network terminates the PDP context due to inactivity. If there is continual activity, the network will maintain the PDP context indefinitely.	4 hours of inactivity at times when the network knows the location of the mobile station. 58 minutes if the mobile station is turned off or goes out of coverage.
Firewall TCP Timer	For mobile-originated communications, the amount of time before the network firewalls terminate TCP connections due to inactivity.	1800 seconds.
Firewall UDP Timer	For mobile-station originated communications, the amount of time before network firewalls terminate UDP connections due to inactivity.	30 seconds.
Firewall ICMP Timer	The amount of time before the NAT (Network Address Translation) router releases the address translation due to inactivity.	10 seconds.
NAT TCP Timer	The amount of time before the NAT (Network Address Translation) router releases the address translation due to inactivity.	1800 seconds.
NAT UDP Timer	The amount of time before the NAT (Network Address Translation) router releases the address translation due to inactivity.	120 seconds.

NOTE: The values listed in the Current Default Value column are subject to change.

The AT&T wireless network maintains a PDP context according to the relevant timer as long as the mobile station maintains a good radio connection to the wireless network. (This is generally the case when the mobile device is stationary and has a strong signal.)

However, if the mobile station travels into weak coverage areas or roams off of the AT&T wireless network, then the PDP context may be lost. When this happens, mobile apps should have the ability to re-initiate a PDP context and to be able to continue operation with a new IP address.