In the last several months I haven't noticed many questions about the Gatekeeper. Perhaps everyone has got the Gatekeeper all figured out and there's no reason to ask questions. Or maybe the Gatekeeper is so impossible to figure out that everyone has given up! Hopefully it's the former and not the latter because the H.
The H. You can use this feature to allow H. The Gatekeeper mediates the communications between the NetMeeting clients and is responsible to call routing and call control.
It's relatively simple to get the Gatekeeper working, but there are a couple of tricks. That way I could avoid issues that sometimes pop up when you change the external interface configuration. Everything seemed to work fine after doing some quick configuration. Policy elements were created to support the rules. Note that Authentication was not being forced on the Outgoing Web Requests listener. I don't believe this is required, but since Q says to do it, I go ahead and do it anyway J.
It also allows me to stick a graphic in here. This function converts external telephone number addresses and alias name addresses to network addresses, allowing users to maintain the same telephone numbers or alias addresses regardless of changes to their network addresses. Note: you can learn more about the functionality and operation of the gatekeeper in a H.
It is important to note that the H. Also, both the audio call control protocol TCP port and the H. Moreover, all TCP connections are outbound , viewed from the calling H.
Note: more technical information how NetMeeting implements the H. It must be obvious that the H. Lucky for us the ISA server incorporates an intelligent H. Let us now examine what configuration options should be used to best fit our goal, taking into account the above mentioned requirements.
This is a very powerful method to adapt NetMeeting to your own taste without placing too much configuration burden on the end user. The following table lists the valid CallTo parameters:. Note: if you set a value of true for secure , you are designating a secure, data-only call. Therefore, data is automatically set to true and av is automatically set to false. If you attempt to set these parameters to a different value, the secure call will fail.
NetMeeting supports two calling models: H. If you are only interested in the data conferencing capabilities and not in the audio and video capabilities, then you might choose the T. No other protocols or ports are involved. As an example, an Ethereal trace of a direct T. As you can see in the above Ethereal trace, the calling T. The first one frame is teared down after a short while frame 12 - 15 and therefore I assume this one is used for some preliminary negotiations at the T.
After the setup of the second connection frame 16 - 17 , some further negotiations seems to happen before the third frame 27 - 28 and fourth frame 30 - 31 connection are established.
It is worth to note that the last two connections are only made after the user at the called T. Also, the last three connections stays open during the lifetime of the NetMeeting session. It should be clear that the T. Unfortunately, when using the T. This is only possible if you use the H. In that case the communication from the calling H. Moreover, as we are not interested in audio and video, we can use a secure connection. So, at this point we can already define the following parameters:.
As an example, an Ethereal trace of a direct H. As you can see in the above Ethereal trace, the calling H. This is the TCP port reserved for the H. Next, the H. Then the H. Take note that the connection setups for the T. As already mentioned before, the ISA server incorporates an intelligent H. The H. To learn more about this exciting piece of software and the various call routing scenarios, check out the ISA Help file and the following articles:.
One of the main requirements, dictated by our network environment, is that the connections should be outbound viewed from the customer side. Also, we like to use the same infrastructure for the internal helpdesk function.
In other words, we can summarize the required call scenarios as follows:. It must be obvious that at the central site we need the H. Also, the first call scenario no H. As a consequence, we need to use a Phone Number as H.
Let us now examine how using the H. Don't worry how things should be configured for proper operation at this moment. We will cover that in the next section. As an example, an Ethereal trace of a H.
Note: the calling H. If you compare the above trace with the trace of a direct H. All connections are outbound viewed from the calling NetMeeting host.
First the H. However, take note that the connection setups for the T. This seems to be the only difference between both traces. In the following figure you see a detailed decode of frame who negotiates the port to be used for the T. As already said, the H.
In the following Ethereal trace you see how the internal client registers with the H. Note: the called H. When NetMeeting is configured to use a H.
In order to achieve this, the gatekeeper uses these H. Zone Management —The gatekeeper provides zone management for all registered endpoints in the zone, for example, the control of the endpoint registration process. Call Management —With this option, the gatekeeper maintains active call information and uses it to indicate busy endpoints or redirect calls. Bandwidth Management —With this option, the gatekeeper can reject admission when the required bandwidth is not available.
Call Control Signaling —With this option, the gatekeeper can route call-signaling messages between H. Alternatively, it allows endpoints to send H. RAS is the signaling protocol used between gateways and gatekeepers. The RAS channel is opened before any other channel and is independent of the call setup and media transport channels. The ITU H. This port initiates the Q. When a gatekeeper is present in the network zone, H. The method chosen is decided by the gatekeeper during the RAS admission message exchange.
It is used to negotiate channel usage and capabilities such as:. Thisis the processes by which H. If an H. This is a UDP datagram addressed to the well-known destination port and transmitted in the form of an IP multicast with the multicast group address A reject message contains the reason for the rejection and can optionally return information about alternative gatekeepers.
Auto discovery enables an endpoint to discover its gatekeeper through a multicast Gatekeeper Request GRQ message.
Because endpoints do not have to be statically configured for gatekeepers, this method has less administrative overhead. A gatekeeper can be configured to respond only to certain subnets. It never remains silent. If a gatekeeper is not available, the gateway periodically attempts to rediscover a gatekeeper. Don't confuse this with the opengk software that comes as a part of the OpenH distribution.
This gatekeeper comes from a different source altogether but is built using the same libraries as opengk. The big difference is that gnugk is a much more complete implementation of a gatekeeper, and opengk is a reference example and is not very useful yet. It will be named gnugk After the download is finished, build the gnugk package:. Now, issuing the gnugk command will launch the gnugk gatekeeper. If you receive an error indicating shared libraries cannot be located, make sure you've got those environment path variables set in your login profile.
If you run into compiler errors, try grabbing the x86 Linux executable from the gnugk site. This is a very capable softphone, and it works well with OpenH In fact, the next section describes how to set it up.
But since the OpenH project produces a phone, too, we'll use it. These examples use screen grabs from the Mac OS X version. The first thing you'll need to do with OhPhoneX is access its Preferences menu option. The Gatekeeper tab of the Preferences window will allow you to specify a gatekeeper, username, password, alias, and E. In Figure , the address of the gatekeeper is The password field is optional; its use is policy-dependent, as gnugk accepts blank passwords.
Finally, the E. Be sure to check the "Use gatekeeper" check box, too. When you close the Preferences window, click the Start Phone button and then click the Console button.
You'll see whether the softphone's registration attempt with the H.
0コメント