The use of H.323 technology offers considerable flexibility to Videoconference Administrators for creating videoconference connections. In the CalREN Video Services (CVS) environment, connection options for your videoconferences include:

Standard Method: Schedule your videoconference using the CVS system.

This method is required if you have more than 2 sites participating, if any sites require ISDN dial-in access, or if you have legacy 4CNet sites who will participate. It is optional if you have only 2 participating sites.

Bypass Method: Bypass the CVS system.

This method is optional if you have only 2 participating sites, and both sites have H.323 capabilities.

Pros and Cons of Using the CVS Scheduling System

Some reasons for using the CVS Scheduling System are:

1. There are more than 2 sites participating in your conference, you have one or more sites who will dial in via ISDN, or one or more of the participants is still on the legacy 4CNet backbone.
2. You want the CVS Help Desk to be able to disconnect and reconnect participants in case of problems.
3. You want your videoconference to appear in the online CVS Schedule.

Given these benefits, why would you choose to bypass the CVS Scheduling System for a given videoconference?

1. If there are only 2 sites, and both have equipment manufactured by the same company (e.g., all Polycom or all Tandberg) there are proprietary features that may improve the quality of the videoconference, if you make a point-to-point connection.
2. If one of the 2 sites is an H.323-capable non-CVS site, you may prefer to connect using IP addresses rather than asking the site to dial in via ISDN. In this case, especially if both sites are not on the CalREN backbone, quality is not assured, but you may discover through testing that it is adequate for your purposes.

Pros and Cons of Using Dial Strings vs. IP Addresses

If you decide to bypass the CVS Scheduling System, you have another decision to consider: will you connect using Dial Strings or IP Addresses?

When you use Dial Strings for videoconferencing, you are sending the videoconference media stream through your CVS gatekeeper/proxy device. This is illustrated below:

Videoconferencing Using Dial Strings

Using Dial Strings provides two major benefits:

1. Media streams sent through the gatekeeper are given priority over other data on the network. That means that if network demand is high, your videoconference is less likely to be affected.
2. On some campuses videoconferences will only work if you use Dial Strings because their videoconferencing equipment is behind a firewall and all calls must go through the CVS gatekeeper/proxy device..

Given these benefits, why would you choose to use IP addresses instead of Dial Strings?

If you are attempting to take advantage of proprietary features because both endpoints are the same brand, you will need to experiment with Dial Strings and IP addresses. There may be some features that will be supported only if you connect with IP addresses.

If you are connecting to an H.323-capable non-CVS site, you will almost always need to use IP addresses to make the point-to-point connection. The exception is that: if the site you want to connect to has a Global Dial String issued by Vide.net and is registered with the North American Root Gatekeeper. In that case, you can dial them directly, but you must ensure your device's dial string is GDS-compliant. (for more information about Internet2 connectivity, please contact Kelly Stack).

When you use IP Addresses for videoconferencing, the media stream goes directly from your videoconferencing endpoint to the other site's endpoint. This is illustrated below:

Videoconferencing Using IP Addresses

There are a lot of factors to consider, and this document doesn't include every possible option, but the following matrix represents our advice for most situations.