SysMonitor: H.323 Registration Events

by ScanSource Catalyst Tech Support on November 16, 2009 · 0 comments

in ScanSource Catalyst,ScanSource Catalyst Tech Support


The next in the series of System Monitor posts covers the H.323 Event messages. There are mainly 3 types of registration events seen in a monitor trace dealing with H.323. Two events are for the registration of a new system phone, the third is a repeated message to keep the phone registered with the gatekeeper.

When an H.323 based IP Phone first begins to communicate with the IP Office it needs to verify what options are supported on the gatekeeper and that the gatekeeper is indeed an IP Office. This process is handled through a Gatekeeper request. In monitor this process is shown as a GRQ, and looks like the example below. Notice the IP address is in hex rather than dotted decimal format. Phones stuck on the Discover screen are at this point. They have sent a GRQ to the IP Office, but have not received a response. They continue to issue a GRQ to the IP address displayed on the screen (which should be the IP Office) until they receive a proper response.

85910767mS H323Evt: Recv GRQ from 0a05090c

The following lines show that the IP Office has found the registration correctly and has in turn responded.

85910767mS H323Evt: e_H225_AliasAddress_dialedDigits alias
85910767mS H323Evt: found number <3335>

Once the IP Office responds to the GRQ and the phone received the information, the phone then proceeds with a registration request. This packet is a bit more particular and includes more specific information about the phone and its extension. These packets are marked as RRQ.

85911046mS H323Evt: Recv: RegistrationRequest; Endpoints registered: 4; Endpoints in registration: 0
85911047mS H323Evt: e_H225_AliasAddress_dialedDigits alias
85911047mS H323Evt: found number <3335>
85911048mS H323Evt: RRQ --- CallSigProtocol is H323AnnexL_P. Go for Avaya 4600IP phone
85911048mS H323Evt: RRQ --- Register extn 3335 using product IP_Phone, version 1.2100
85911255mS H323Evt: Recv NSM from 0a05090c
85911255mS H323Evt: Recv SwitchInfoRequest from 0a05090c

After the phone receives the confirmation about registration, the user’s profile is delivered to the phone and it begins its normal operation. About every 50 to 60 seconds you should see another registration request that keeps the phone in a current registration status.

86630288mS H323Evt: Recv: RegistrationRequest; Endpoints registered: 5; Endpoints in registration: 0
86685292mS H323Evt: Recv: RegistrationRequest; Endpoints registered: 5; Endpoints in registration: 0
86740287mS H323Evt: Recv: RegistrationRequest; Endpoints registered: 5; Endpoints in registration: 0

If these registration packets are missed by the IP Office, the phone is forced to restart the registration process. This is sometimes viewed as the phone rebooting. Rarely is this a problem with the phone or the IP Office. Typically it has to do with a network delaying or discarding one of these packets.

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