'H.323 is now focused at the service provider segment and a number of features have been added on to it to make the protocol extremely scalable'

What is the latest about H.323?

H.323

was originally developed as a LAN protocol, built for audio, video and data

conferencing. And as soon as the first version was developed, the attempt was to

place video and audio calls over the Internet. Even in version 1, Net Meeting

(an H.323 version 1 based product) was built for Internet use. It was clear that

LAN strongly limited the concept of H.323. Subsequent versions, versions 2, 3

and 4, have been focused on building a protocol that works well in a WAN,

especially the Internet and private video, audio and data networks.

The protocol is now focused at the service provider segment and so, the

latest on H.323 is the number of features that have been added on to it to make

the protocol extremely scalable.

So, are you saying that the focus is now towards popularizing H.323 in the

service provider/IP-telephony market?

Well, H.323 is already popular in the IP-telephony space. In

fact, it is the only protocol that is actually deployed in any significant size

network. It has been growing quite rapidly in the recent years. Take the case of

China, which has deployed the largest VoIP network in the world. The entire

network is based on the H.323 protocol.

What are the additional significant features in the

versions 2, 3 and 4?

Probably, one of the most significant additional feature in

H.323 (version 2) is ‘Fast Connect’, the facility allowing users to

establish a call much more quickly than in earlier versions. Earlier, there

needed to be an exchange of a few network messages before the actual call could

be placed, but by using Fast Connect, the call can be established by a simple

message exchange in each direction. Some of the other significant features added

in its subsequent versions are H.245 tunneling, Annex E/H.323, alternate

gatekeepers, etc.

How easy or difficult is it to implement H.323?

A. The first thing that people bring up while speaking about

competing exchange protocols, such as the Session Initiation Protocol (SIP), is

its ease of use. They feel that SIP is wonderful, since it can be easily setup.

But what they do not realize is that SIP does not have all the features for it

to be deployed in a telco-standard solution.

H.323 is much more complex because telecommunications is

complex. So, a protocol that meets all the market requirements, needs to be

something that has some level of complexity. At the same time, it is not as if

H.323 is impossible to establish. There are companies who have a large list of

products and services, all of which are based on the H.323 protocol and are

working well.

Are these protocols (H.323 and SIP), competing protocols

or do you believe that H.323 is more popular?

H.323 is definitely more popular than SIP for a number of

reasons. H.323 is an older and mature protocol. It has all the features

necessary to deploy and operate a decent size network. Today, we can build a

H.323 based network, which performs VoIP, addresses translation, routes calls

anywhere in the world and then actually terminates them. SIP, on the other hand,

still has many limitations.

What about the enterprise segment? Is SIP more popular

there?

No, it is not. It is like this, in an enterprise space, if

you are doing only voice on a network then you have to realize that the most

popular solutions are proprietary, such as Cisco’s own ‘Call Manager’

solution. For instance, the IP-phone works on the Cisco Call Manager software.

Cisco Call Manager, instead, uses the H.323 protocol to place calls.

The H.323 has been around longer than SIP. SIP in that sense

has to play ‘catch-up’ to H.323 in the IP-telephony space.

Coming to the issue of security, is it possible for people

to intrude in a network that is setup on the H.323 protocol?

Well, Yes. It is possible for someone to breach and listen to

the conversation on an H.323 based network. But, while it is definitely possible

for someone to intrude into conversation on the network, it must also be said

that it is possible to encrypt media streams on the network as well.

Security can be built in to the network based on H.323 using

a H.235 protocol. We are currently working on the second version of the H.323,

which helps in deciding how to build a secure network, end-to-end. Once H.235 is

enabled, you can authenticate the user and devices, authorize the devices at

both ends and encrypt the video streams and the call signaling. Therefore, a lot

of options exist on what can be done. Such options, in fact, are available in

both the versions of H.235, the latter version having a few additional options

and features.

However, it is a matter of choice whether a service provider

would want to install this system or not. Many service providers do not require

encrypting, the reason being that encrypting slows down the call processing and

handling. Moreover, service providers have reason to believe that since they

control the entire network, it will provide the necessary security. The fact is

that the data that comes into a network is such that if any person wants to keep

track of it or tap into it, it can be done.

A lot of companies are using toll bypass by using calling

cards to place calls over IP networks. Say in China, they do this by placing a

call on the PSTN to the gateway, which authenticates the user it is H.323 that

does this authentication between the user and the gateway. Voice will then be

carried over IP and is not encrypted as it is within the service provider’s

networks who has physical control over the cables.

The final verdict is that it is possible to comprehensively

encrypt an H.323 based network, but the level of security enabled is a factor

depending on the requirements of the customer from the service provider.

In India, PSTN networks are still the way of life. We are

a long way off from carrier class IP-based networks. How will H.323 work in such

an environment?

I am really not too sure of the situation in India right now

but I can take the example of China, a few other Asian countries and the US. In

these geographies, it is very clear that IP-networks are a way forward. Due to

the population density of most cities, it makes a lot of sense for service

providers to establish and run high-speed broadband cable networks into

residences and offices. Here, the PSTN will be replaced by one or a few

high-speed broadband connections to buildings. IP-based services will happen

because people will demand it. And once such a network is in place, adding voice

to it it is easy.

India is still a bandwidth deficit country. Will running a

multimedia enable H.323-based protocol into the bandwidth resources of the

nation?

A. Bandwidth utilization is really not a function of the

H.323 protocol but of carrying VoIP. The actual bandwidth consumption by the

H.323 is very small, the bandwidth used to carry VoIP, Real Time Protocol (RTP,

the protocol that also runs SIP), will use greater bandwidth. Even here, voice

can be compressed by using CODEC’s, thereby keeping bandwidth utilization to

the minimum.

Can QoS be guaranteed on an H.323 based network?

For the specific purpose of assuring QoS over networks, a

protocol called RSVP is used. However, most service providers are not using the

protocol because it is cheaper to just install a high-speed optical fiber

network with excess bandwidth to carry voice (apart from data). This is because,

the cost involved in managing a lower installed bandwidth is far more than not

managing a high-bandwidth. Therefore, service providers’ prefer to setup

higher bandwidth solutions in the first place.