Gatekeeper Signaling: LRQ Blast
In Figure 8-10 and Archetype 8-2, aback bang LRQ is used, Attendant A will simultaneously
send LRQs to all three gatekeepers that bout the area prefix.
Chapter 8: Configuring H.323 Gatekeepers 459
Note With consecutive LRQs, there is a anchored timer aback LRQs are sent. Even if
Gatekeeper A gets an LRJ aback anon from Attendant B, it will delay a anchored amount
of time afore sending the abutting LRQ to Attendant C and Attendant D. You can speed
up this action by application the lrq lrj immediate-advance command.
Gateway A
V
ARQ
LRQ
GKA GKB
LRQ
LRQ
GKC
GKD
Gatekeeper A Attendant B
Gatekeeper C
Gatekeeper D
Figure 8-10 Bang LRQ
Example 8-2 Bang LRQ Configuration
GKA(config)#gatekeeper
GKA(config-gk)#zone bounded GKA cisco.com
GKA(config-gk)#zone alien GKB cisco.com
GKA(config-gk)#zone alien GKC cisco.com
GKA(config-gk)#zone alien GKD cisco.com
GKA(config-gk)#zone prefix GKB 1408555.... blast
GKA(config-gk)#zone prefix GKC 1408555.... blast
GKA(config-gk)#zone prefix GKD 1408555.... blast
If all three acknowledgment with a absolute acceptance (that is, an LCF), Attendant A chooses
which one to use. Attendant A can clothier the best by application the amount and antecedence keywords
at the end of the area alien account as follows:
GKA(config-gk)#zone alien GKB cisco.com amount 50 antecedence 50
GKA(config-gk)#zone alien GKC cisco.com amount 51 antecedence 49
GKA(config-gk)#zone alien GKD Cisco.com amount 52 antecedence 48
The amount and antecedence command options charge to be advised anxiously for actual operation.
The absence amount is 50, in the ambit 1–100. In the example, you see the three gatekeepers
have costs of 50, 51, and 52. This agency Attendant B has a lower amount than
Gatekeeper C, and Attendant C has a lower amount than Attendant D. Therefore,
Gatekeeper B will be called first, and again Attendant C, and assuredly Attendant D.
The antecedence can additionally be set. The absence for this advantage is additionally 50 in the ambit 1–100. In
the example, the gatekeepers with a college amount additionally accept a lower priority. Aback anniversary of
the gatekeepers allotment an LCF to Attendant A, a accommodation as to which attendant the
call should be forwarded to can be fabricated based on either amount or priority.
You can accredit amount and antecedence ethics apart of anniversary other. You ability choose
to accredit alone a amount or a antecedence to a specific gatekeeper. If the ethics you accredit to a
specific attendant are college or lower than the absence values, and there are added gatekeepers
that are application absence ethics for amount and priority, alarm acquisition ability booty these
unexpected paths. In the afterward syntax,
GKA(config-gk)#zone prefix GKB 1408555.... blast
GKA(config-gk)#zone prefix GKC 1408555.... blast
GKA(config-gk)#zone prefix GKD 1408555.... blast
the bang advantage has been added to the area prefix commands. This advantage is an important
part of the agreement that is generally overlooked. The bang advantage allows
Gatekeeper A to accompanying accelerate LRQs to Attendant B, Attendant C, and
Gatekeeper D. If the bang command advantage is omitted, the attendant will use the
default method, which is to accept the attendant based on sequence.
To summarize, Attendant A receives an ARQ from a aperture for 1408555xxxx.
Gatekeeper A again blasts LRQs to all gatekeepers, which in this case are Attendant B,
Gatekeeper C, and Attendant D. Attendant A will use the amount and antecedence ethics to
evaluate the accustomed LCFs to actuate area the alarm should be forwarded. In this case,
if all the after gatekeepers acknowledge with LCFs, Attendant A will use the priority
and amount ethics and accept Attendant B as the attendant to which to advanced the call.
Intrazone Alarm Setup
Figure 8-11 shows the arrangement of the signaling contest and the basal signaling that takes
place amid a aperture and gatekeeper.
Figure 8-11 Intrazone Alarm Setup
The accomplish of this intrazone alarm bureaucracy are as follows:
1. Buzz A dials the buzz cardinal 408 5555-2001 for Buzz B.
2. Aperture A sends an ARQ to the gatekeeper, allurement permission to alarm Buzz B.
3. The attendant does a lookup and finds Buzz B registered to Aperture B and
returns an ACF with the IP abode of Aperture B.
4. Aperture A sends an H.225 alarm bureaucracy bulletin to Aperture B with the buzz number
of Buzz B.
5. Aperture B sends an H.255 alarm proceeding bulletin to Aperture A.
6. Aperture B sends an ARQ to the gateway, allurement permission to acknowledgment Aperture A’s
call.
7. The aperture allotment an ACF with the IP abode of Aperture A.
8. Aperture B and Aperture A admit an H.245 adequacy barter and accessible logical
channels.
9. Aperture B sets up a apparent old blast account (POTS) alarm to Buzz B at 408 555-
2001.
10. Aback Buzz B answers, Aperture B sends an H.245 alarm affix bulletin to
Gateway A.
11. Dual RTP streams breeze amid gateways.
Chapter 8: Configuring H.323 Gatekeepers 461
Phone A Buzz B
801 555-2001 408 555-2001
1 9
Gateway B
Gatekeeper
GK
Gateway A
V V
4
5
8
10
11
2
3 7
6