White Paper: Multimedia delivery using corporate intranets

Today's technology allows multimedia applications to be run over a “traditional” data network infrastructure. This white paper...

Today's technology allows multimedia applications to be run over a “traditional” data network infrastructure. This white paper gives an insight into this how this concept works

There are several compelling arguments for transitioning multimedia applications to the corporate intranet. These include cost savings, network management simplification, benefits of "networking" and putting these applications in the most flexible position to take advantage of technology advances.

In order to support multimedia applications today within a corporate environment it may take three or more "networks" to do that. The data network needs to exist in order to connect mainframe-based or client/server applications together across the corporation. The telephony applications, comprised of PBXs connected together via the Public Switched Telephone Network (PSTN), is almost always present. And the corporation may have one or more forms of video conferencing, each running on its own switched or leased line network. International corporations may have multiple instances for each of these "networks'"

There is a lot of complexity involved in managing all of these networks. Each of them has its own cost basis, user issues and management difficulties. Migrating as much of this multimedia traffic as possible to one networking infrastructure can improve performance and reduce management costs.

Costs can also be improved by the selection of the type of intranet technology that is used. Choices typically include Asynchronous Transfer Mode (ATM), frame relay and Internet Protocol (IP) running over leased lines. In many cases, the recurring cost of running these applications over a single network infrastructure can be far cheaper than the previous case of separate networks for each application. The amounts vary and are dependent upon the traffic patterns of each application such as tariff structures.

As data and multimedia applications merge onto a single intranet, the networking benefits of that convergence can also be important. These include: the ability to broadcast real-time voice and video to selected sites; network addressing flexibility to support mobile worker follow-me; and corporate work-at-home programs, as well as the simplicity of the application working the same at any point on the network no matter what part of the world it may exist in.

Another argument for the "one" intranet model is that of enjoying the flexibility to migrate applications as the technology migrates. This is very clear when one considers what the local area network model has done for so many data and multimedia applications. The fast pace of LAN and IP-based application developments will only speed up in the future. By having the corporate LAN and multimedia applications tied together over intranets, the flexibility to take advantage of these advances is maintained.

What makes for a "good" intranet?

In order to support multimedia applications in a high quality fashion, an enterprise intranet must provide the following:

Low latency for the voice and video traffic

Selectable quality of service (QoS) for different data applications depending upon their needs

Low operational costs (at least relative to a non-intranet model)

Low enough deployment costs for a quick return on investment (say less than a year)

It is absolutely critical that the voice and video applications being placed on the intranet experience as little a delay as possible in traversing the network. If quality is to be high enough to migrate from the PSTN, the one way delay has to be less than about 250ms. If the intranet delays mount much over that, the users will experience poorer quality than was previously experienced with the PSTN network.

QoS is not just limited to the voice and video. There are many data applications that are also delay sensitive, particularly mainframe-based applications that require minimum round trip response times.

Low operational and maintenance costs of network are also very important considerations.

What are the intranet infrastructure choices?

The basic choices for the creation of enterprise intranets are ATM-based networks, frame relay-based networks or IP-based networks which can run on top of ATM, frame relay or natively on leased lines or dial up links such as ISDN. Each of these has advantages and disadvantages when multimedia applications are considered as traffic types that will need to exist with the data.

ATM technology has some real benefits for multimedia applications. It is typically a high speed (never less than T1) and it has been engineered from its beginning to carry data, voice and video traffic. It has the QoS measures built into it and it is very low delay due to its relatively small frame structure. But ATM also has some very serious drawbacks. It is not deployed widely and suffers from a lack of competitive providers. It is inefficient at low speeds and so it is not usually deployed in the low bandwidth selections which the branch offices require (fractional T1). The deployment cost is high due to the high cost of ATM hardware. The ATM service offerings are usually priced at premium levels as well.

Frame relay technology is another infrastructure alternative that can serve multimedia applications well. Since it has a very flexible frame structure with low overhead, it can serve real time multimedia applications that desire relative small frame sizes as well as data transfer applications that work best with large frame structures. Typical latency on a switched public or private frame relay network is low and it can efficiently run down to low data rates to keep it economical for small office sites. Frame relay is also a very competitive offering with many service providers in most markets. One feature not always offered in frame relay is that of predetermined QoS. Although there is a lot of work going on and some providers are supplying it, it is not available in the same way everywhere by all carriers and providers. In spite of this, frame relay has proved itself to be able to run multimedia applications, especially voice, in a high quality fashion.

The Internet Protocol has the distinct advantage in that it really is everywhere. Most LANs are IP-based and many of the best multimedia applications being constructed today are IP-based. IP applications can ride on top of ATM or frame relay as well as HDLC-based leased lines. IP does suffer from high overhead and high latency as it is passed through router hops and there is no QoS today. And yet, IP must be considered a viable multimedia networking solution because it is nearly everywhere.

The best enterprise intranet is composed of a hybrid of all of the above. IP applications must be supported natively at the LAN and application point. The most efficient wide area network carriage needs to be employed to transport that application with the lowest delay and least possibility of congestion. The major issues that may be present in a network must be considered up front. Chief among them is an understanding that data and multimedia traffic are indeed different:

Most data traffic is not sensitive to delay; voice is quite sensitive

Data traffic tends to be asymmetrical in nature; voice and video traffic are not

Video traffic consumes relatively large and constant chunks of bandwidth

Network congestion causes loss of information to real time traffic like voice and video

What to look for in a voice application on an enterprise intranet?

In the case of migrating a voice application to an enterprise intranet there are several important considerations. The first is compatibility between the network equipment and the PBX equipment and PBX features. The second is the choice of the networking infrastructure to deliver the expected quality and performance that is expected. Examples of the PBX compatibly issues are the following:

The networking equipment must support the existing PBX network numbering plans

Network equipment must support all of the PBX interface ports

Network equipment must support the required PBX-to-PBX signalling methods and standards

The need to switch calls anywhere across the network no differently than the PSTN would provide

The choice of the networking infrastructure type is also a key decision:

Enough bandwidth must be available to handle the voice as well as the data at the expected peak traffic levels; voice is not "free"

Enough QoS that the voice video and data will all be delivered with the appropriate minimum delay and packet loss criteria

Ability to painlessly grow the network as the applications get larger and traffic patterns change

Conclusion

For all of the above considerations, a frame relay-based intranet that can transport the voice applications with minimal latency and queuing as well as the IP data traffic is a sound choice. Frame relay networking equipment, which can also provide IP-based multimedia gateway functions onto the frame relay intranet, is also a very important function in order to future proof your intranet.

Compiled by Will Garside

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