H225 RAS Messages

by | Mar 4, 2010 | H.323, IOS, Lab, Written Theory

Here are the different messages used by the H225 RAS signaling which can occur between endpoints and GK.

  • Gatekeeper Discovery : used by endpoints to register

    • GRQ : Gatekeeper Request
    • GCF : Gatekeeper Confirm
    • GRJ: Gatekeeper Reject
  • Registration/Unregistration : used by endpoints to register or unregister their address and their zone withtin the GK.

    • RRQ : Registration Request
    • RCF : Registration Confirm
    • RRJ : Registration Reject

    • URQ : Unregistration Request
    • UCF : Unregistration Confirm
    • URJ : Unregistration Reject
  • Admission Control : These messages are used for all admission control and bandwidth management

    • ARQ : Admission Request
    • ACF : Admission Confirm
    • ARJ : Admission Reject
  • Bandwidth Control : these messages are used if you want to change the amount of bandwidth during a call

    • BRQ : Bandwidth Request
    • BCF : Bandwidth Confirm
    • BRJ : Bandwidth Reject
  • Endpoint Location : These messages are used to retrieve contact information ( also with Directory GK)

    • LRQ : Location Request
    • LCF : Location Confirm
    • LRJ : Location Reject
  • Status Information : They are used to retrieve a status information

    • IRQ : Information Request
    • IRR : Information Response Request

H225 call control signaling is on TCP/1720 and uses Q931 messages to establish, maintain and tear down calls. these messages are

  • Setup
  • Setup Acknowledge
  • Call Proceeding
  • Progress Alerting
  • Connect
  • User Information
  • Release Complete
  • Status Inquiry
  • Status
  • Information
  • Notify

So in general , here is the following reminder: While h225 call control signaling can be used for call setup, H245 must be used to determine a master/slave relationship, exchange terminal capabilities, logical channel signaling and DTMF relay.

H323 Stack

by | Mar 4, 2010 | H.323, IOS, Lab, Written Theory

We have already spoken about Gatekeeper signaling in this previous post but let’ be more general and see what are the common elements of H.323 stack.

We have H225 RAS ( Registration Admission and Status) which is used between the GK and H323 endpoints.

But under normal operation , we have also H225 which is the call control and signaling part of the H323 stack. So we use it to establish connections.

We have also H245 which is the negotiation part of the H323 stack. So it is during this stage that you can exchange capabilities/codecs, establish logical channels. It is in fact all settings for the transmission of the media.

Reminder:

  • H225 RAS  => UDP/1719
  • GK Discovery => UDP/1718

The Multicast GK discovery uses IP Address 224.0.1.41

Gatekeeper Basic Configuration

by | Mar 2, 2010 | H.323, IOS, Lab, Written Theory

Here is a basic definition for the gatekeeper config:

!
gatekeeper

zone local oks ksiazek.be 10.0.0.1 1719

zone prefix oks 1234*

gw-type-prefix 1#* default-technology

bandwidth total zone oks 1024

bandwidth session zone oks 128

no shutdown

!

The zone local defines the Gatekeeper’s name , the domain to which it belongs and its IP Address and the TCP port used.

The zone prefix specifies the Gatekeeper’s name and the prefix associated within the zone list.

The gw-type-prefix will help to route calls if the called number doesn’t correspond to an E.164 number.

The bandwidth total zone defines the maximum aggregate bandwidth that you can use within this specific zone.

The bandwidth session zone defines the maximum bandwidth available for a session in the zone ( so this is the bandwidth for a call)

No shut activates the Gatekeeper’ configuration.

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