Changing IKE Transmission Parameters

When IKE negotiates keys, the speed of transmission can affect the success of the negotiation. Normally, you would not need to change the default values for IKE transmission parameters. However, when optimizing key negotiation over very dirty lines, or when reproducing a problem, you might want to change the transmission values.

Longer duration times enable IKE to negotiate keys over unreliable transmission lines. You can lengthen certain parameters so that initial attempts succeed. If the initial attempt does not succeed, you can space subsequent attempts to offer more time for success.

Shorter duration times enable you to take advantage of reliable transmission lines. You can more quickly retry a failed negotiation to speed up the negotiation. When diagnosing a problem, you might also want to speed up the negotiation for a quick failure. Shorter durations also enable the Phase 1 SAs to be used for their lifetime.

How to Change the Duration of Phase 1 IKE Key Negotiation

1. Change the default values of the global transmission parameters on each system.

   On each system, modify Phase 1 duration parameters the /etc/inet/ike/config file.

   ### ike/config file on system
   
   ## Global parameters
   #
   ## Phase 1 transform defaults
   #
   #expire_timer      300
   #retry_limit         5
   #retry_timer_init    0.5 (integer or float)
   #retry_timer_max    30   (integer or float)

   expire_timer

   The number of seconds to let a not-yet-complete IKE Phase I negotiation linger before deleting the negotiation attempt. By default, the attempt lingers for 30 seconds.

   retry_limit

   The number of retransmits before any IKE negotiation is aborted. By default, IKE tries five times.

   retry_timer_init

   The initial interval between retransmits. This interval is doubled until the retry_timer_max value is reached. The initial interval is 0.5 seconds.

   retry_timer_max

   The maximum interval in seconds between retransmits. The retransmit interval stops growing at this limit. By default, the limit is 30 seconds.

2. Refresh the ike service.

   # svcadm refresh svc:/network/ipsec/ike

Example 22-14 Lengthening IKE Phase 1 Negotiation Times

In the following example, a system is connected to its IKE peers by a high-traffic transmission line. The original settings are in comments in the file. The new settings lengthen the negotiation time.

### ike/config file on partym
## Global Parameters
#
## Phase 1 transform defaults
#expire_timer   300
#retry_limit      5
#retry_timer_init 0.5 (integer or float)
#retry_timer_max 30   (integer or float)
#
expire_timer 600
retry_limit 10
retry_timer_init 2.5
retry_timer_max 180

Example 22-15 Shortening IKE Phase 1 Negotiation Times

In the following example, a system is connected to its IKE peers by a high-speed line with little traffic. The original settings are in comments in the file. The new settings shorten the negotiation time.

### ike/config file on partym
## Global Parameters
#
## Phase 1 transform defaults
#expire_timer   300
#retry_limit      5
#retry_timer_init 0.5 (integer or float)
#retry_timer_max 30   (integer or float)
#
expire_timer 120
retry_timer_init 0.20