LAN-Telephony: Hassle-free Communication

I got a call from a customer of mine asking me to offer a solution for his LAN

infrastructure that would save him a whole lot of money.

When I asked him what he really wanted, he replied "Cost saving and

getting voice across on a single cable infrastructure, and integration of more

applications.’’

The result: A solution called ‘LAN telephony’, which provides the common

infrastructure for voice and data, and enables integration of new IP

applications.

LAN

Telephony



Simply put, LAN telephony is a communication mechanism that uses the

enterprise’s data network to transmit packetized voice. This arrangement

eliminates the traditional time division multiplexing (TDM) techniques that

require the discrete two-wire approach, one for data and another for voice. Even

though it sounds and looks deceptively simple, it is an arduous task for the

market to accept and implement this emerging communication infrastructure.

Traditionally, enterprises have a telephony infrastructure using proprietary

system called PBX. Typically, an ISDN PRI or E1 line is leased from the carrier

and connected to the public switched telephone network (PSTN) cloud, enabling

voice connectivity across the enterprise. Incidentally, this system has worked

extremely well for a number of years.

Even though PBXs are proprietary systems, they were built taking into

consideration both reliability and uptime. It was and is always assumed that

voice network will be always available and it just works. But for most of its

benefits, PBX is a very closed system.

The entire voice system works over the standard telephone cable using TDM,

but the data network typically runs on a totally independent cable

infrastructure and never communicates with the traditional voice system.

Now the burning question is: how to bring down the cost of infrastructure

without compromising upon the functionality of both voice and data?

A Different Ring Is Needed



LAN is one of the oldest infrastructures of an enterprise. It was created to

address the concerns of information managers (IS) way back in 1998, when NBX

(now part of 3Com) shipped the first packet-based handset on Halloween.

But the time has arrived for enterprises to take the existing infrastructure

details and integrate new applications, which aid in bringing down the total

cost of ownership.

At the same time, newer IP applications are bringing a whole new set of

changes in the LAN infrastructure and hence, it is essential to understand and

accommodate these changes and get going.

According to the analysts, LAN telephony market will be about $14 billion by

2005. In 2001, the US alone contributed $1 billion to the LAN telephony market.

Market Trends



Even during the economic downturn, most of the vendors have seen the LAN

telephony market grow. IP is no longer scary. Concerns about network

reliability, uptime, administration and maintenance work are no more the

concerns of IS managers.

Most of the PBX vendors clearly accepted the market reality and announced

their LAN telephony support strategy. However, many of those shipments are

add-ons to the existing PBXs.

Mostly the circuit-switched voice infrastructure is connected to IP, by using

gateways in the LAN environment and is then transmitted across the LAN and

finally, to the IP handset. However, all telephony installations may not use IP,

many utilize other packet formats. And also not every LAN telephony

installations involve a packet handset. Often the call is converted back to

circuit; either at the desktop or workgroup (also referred as nodes or zones)

level, and a standard analog and digital set can be used.

Why LAN Telephony Now?



A tremendous price advantage in the long run is what LAN telephony is all

about, apart from, of course, offering easy manageability and tighter IP

application integration in the LAN environment.

It wins hands down on four counts:



n Price:

LAN telephony systems are 30—40 percent cheaper than the traditional TDM, PBX

solutions. Packet handsets are the only expensive part in the entire solution

(some vendors offer almost all features of packet phone over the digital

phones).

n Administration:

LAN telephony systems neatly fit in the LAN environment like any other IP

devices in the enterprise. Benefits include hassle-free maintenance, no need to

depend on the traditional voice engineer or a technician to solve any

voice-related problems. Data administrators themselves can handle all the

problem call escalations.

n New

IP applications: Most of the software

vendors have already accepted IP as the default protocol for all

applications. Both the availability of IP-related products and the skillset of

programmers have become very common. New IP applications can be easily

integrated into the existing data network application infrastructure.

n Geographic

Reach: It offers multi-site connectivity across different offices spread out

geographically, offering low communication infrastructure cost. Collaboration

and conferences can be held in real time across multiple offices

Technical Challenges



Even though LAN telephony appears to be a simple and clean technology, the

first and the last commandment is the voice quality along with complete

reliability.

Technically, the parameters, which influence the data networks, may not be

acceptable by the voice network. By their very nature, voice and data are

different and the devices, protocols, and the technology, which handle them are

also different in nature

Following are some of the IP-based QoS techniques generally used by the

equipment manufacturers to address technical problems:

n Compression

Technique: Used to address bandwidth-related issues at the cost of latency

n Buffering:

Also referred to as jitter. In voice packetization, the packets are sent across

the network and some times not all the packets arrive in the preferred order.

This phenomenon of time spent waiting for a packet to arrive and re-sequencing

packets is called ‘jitter’. Jitter/buffering uses various algorithms for the

calculation of packet movement (i.e. when to move forward with or without

packet), in order to provide the best speech quality.

n Silence

Compression: Silence compression has the intelligence not to send empty

voice packets when the user is in silent mode or not speaking for that

particular time. This technique is used to improve bandwidth efficiency.

Vendor Selection



Two sets of vendors are fighting it out. One set of people are from pure PBX

background (or traditionally voice people) and the second set of people are from

pure data communication background. Even though the final solution from both the

vendors offer the same result, their approach is totally different.

Data communication vendors claim that they have a ‘pure IP’ solution and

they call it IP PBX solution, whereas telecom giants claim that they have a ‘converged

solution’ (also referred to as converged PBX).

Whatever be the names and terminologies, both of them are trying to increase

their market share and leadership, and at the same time retain the existing

customer base.

Which one is better?



It all depends on your business. It is very essential to understand the

business needs before leaping into any technology and approach.

In case of IP PBX vendors approach, the entire architecture is based on IP

infrastructure, which is currently dominating the market. IP PBX architecture

uses packetized voice for all operations until the call actually leaves LAN and

enters the PSTN cloud, which is traditionally circuit switched.

But in case of a ‘converged PBX’ solution, both TDM and IP routes are

adopted while providing the final solution. Converged PBX offers TCO benefits

and these benefits are directly passed on to the end users.

All major communication vendors are supporting LAN telephony and they have

announced their strategy and approach towards the IP telephony solutions.

Most of the products are already working and yielding the expected results in

the enterprise. However, some of the technical challenges need to be addressed

during the actual implementation. The real implementation of LAN telephony and

system integration activity is the key for true success of LAN telephony.

Lower per-user equipment cost, reduced administration cost, movement towards

standards like H.323, and SIP, are also going to be the key drivers for the LAN

telephony market.

Prashanth S Rao



Solutions architect, Nortel Networks India