Convergence TABLE OF CONTENTS Executive Summary 1 Introduction 2 Part I Business Factors 3 What is Convergence? 3 Toll Bypass 3 Utilization Getting Your Moneys Worth 3 Part II Technical Overview 4 Mixed-Media Requirements 4 Problems: – Delay 4 – Packet Loss 5 – Jitter 5 Network Technology 5 Voice over ATM 5 Voice over Frame Relay 6 Voice over IP 7 Inter-Vendor Support 8 H.323 8 Part III Implementations 10 Types of VoIP Implementations VoIP through a router 10 LAN Telephones 10 IP PBX 11 VoIP Gateway 12 Conclusion 13 Appendix A Works Cited 14 Illustrations Chart 1 Cost of International Voice Calls 3 Graph 1 Long 1-Way Voice Transmission 4 Chart 2 Summary of H.32x Standards 8 Picture 1 Converged Network Architecture 9 Picture 2 H.323 Architecture 9 Picture 3 VoIP through a Router 10 Picture 4 LAN Telephones 11 Picture 5 IP PBX 11 Picture 6 VoIP Gateway 12 Picture 7 Ciscos Consolidated Data-Voice Network 13 EXECUTIVE SUMMARY The universal belief, today, is that IP will become the transport for virtually all communications traffic. Yet, there are still fundamental issues involved with converging voice and data traffic onto the same medium. Many vendors and standards organizations are working on developing solutions that interoperate together. It is no longer desirable to have proprietary products that do not work outside the company walls. Users expect a quality of service equal to that which they are already experiencing.
By making use of intelligent network design, advanced routing protocols and open-industry architecture this dream can become a reality. Umbrella standards, such as H.323, spell out a model that is non-vendor specific for providing voice, video and integrated data. Merging telephony and data will have two major benefits. The first, and most important to any businessperson, is the impact on the IT budget. Within the IT budget three areas will have savings: IT personnel, network equipment, transmission services. The IT personnel will have to be knowledgeable in both data and voice networking. Thus reducing the need for separate teams.
In most cases the need for forklift upgrades has been eliminated. By simply adding hardware components and software the migration can begin. The second, and more significant than the first, is the new applications that this makes possible. Combining voice and data onto one packet infrastructure enables new capabilities that are not possible with separate networks. Together they produce a synergistic effect that can give a company customer interaction capabilities like never seen before.
The network itself can be chosen for facilitating voice and data. The most impressive of which is voice over ATM. ATMs high speed, high availability, scalable architecture molds well to the requirements of convergence. Voice over IP is a more general technology allowing a variety of networks to run underneath its mature, sophisticated protocols. Several implementations allow for a gradual migration that many times uses much of the existing hardware. By properly planning and slowing making the migration, a company can be assured that end result will be a success.
INTRODUCTION Converging voice and data communications onto the same network is, by no means, easy. The two, although at first seeming alike, they are actually quite different at heart. Networks can be classified in one of two ways. The network is said to be connection oriented when a direct connection, physical or logical, is setup before data is transferred. Connection-less, however, simply addresses information and sends it to the recipient.
Every packet is addressed and must be routed through the internetwork, meaning packets can take several different paths to the source. Voice networks are circuit-switching networks. They are connection oriented, whereby the caller and the called party have a connection established before talking. Data networks are a packet switching technology. No setup occurs when data is sent and received. Each individual packet must receive a network layer header with the destination address. When the packet is passed between routers, not all packets take the same path.
This is because routing protocols have intelligent route selection capabilities that allow load balancing and other features. It is easy to see intrinsic difference. How do you make connection-less behave as connection oriented? Voice service has been highly refined for many years. Users have become accustomed to highly available, clear, fast connections when making phone calls. This presents a major quality of service (QoS) hurtle that must be overcome for Voice over IP to be accepted Protocols have been developed that use certain bits within the IP header to define the Type of Service (ToS). Currently, many vendors have used these bits in a proprietary manor but the IETF has decided to redefine them.
Another issue arises when defining QoS, what do you do differently with high priority traffic versus low? To this RSVP has answered with the ability to define a route through the network and then have high priority (Voice) traffic routed along that same path. The leaps and bounds that technology has made in recent years have opened the door to faster routers with much more sophisticated routing protocols. Enabling higher and higher data rates that are necessary for the limited delay requirements of voice traffic. Even network design has been rethought to allow for speeder and more reliable connections. Innovations and education from vendors like Cisco, 3COM and Nortel have lead to lowered congestion on network segments.
This enables networks to scale as large as the company and maintain similar features across the whole enterprise. Throughout this paper it will discuss both business and technical issues associated with migrating towards a seamless voice and data network. It would be unwise to try to implement these changes too quickly. The quality of service users are accustomed to must not change. The object of networking is to increase productivity and decrease cost.
A converged network promises both but the migration process must be well managed in order to ensure a smooth transition. Business Factors What is Convergence? Convergence has been a hot topic for many years. The dream spawned by the Internets wealth of possibilities, of a combined voice, video and data network has fueled vendors to come up with an industry-wide, non-vendor-specific solutions. More importantly for business this dream spells big savings over the long run. Three areas of the IT budget should see savings. IT Personnel Rather than having data-network personnel and voice-network personnel.
IT staff will be required to be knowledgeable in both areas and therefore cutback to one slightly larger team. Network Equipment Although at first, in order to establish the technology, cost may be significant. By using Computer Telephony Integration (CTI) the need for dedicated, specialized devices can be reduced. Also packet switching is soon becoming as much as 20 50 times more cost-effective than circuit switching because of its connection-less nature. Transmission Services Mainly dealing with cost savings from non-US calls. Convergence is defined as combining voice and data in one media without channellizing.
There are basically five ways of doing this: Point to Point digital circuits LAN Frame Relay Corporate intranet Internet Toll Bypass The global market that we live in today demands that businesses conduct calls with foreign countries. The price of these calls can have a high impact on the IT budget (see chart 1). Destination Country Cost Per Minute Ireland US$0.40 Japan US$0.35 Israel US$0.75 Brazil US$0.55 For most large companies, US calls should not cost more than three cents a minute. The cost savings for international calls, on the other hand, by using VoIP is obvious after considering the volume of calls that occur. -Packet Magazine V.12, N.2, page 63 Utilization Getting your Moneys Worth Its a fact that data communications is bursty. Meaning, data transfer peaks for a moment and then is stagnant. Consider when you are browsing on the Internet.
Data transfer is high as the page downloads. Once loaded, you sit and read. The connection is idle and bandwidth is not being used. For a business, this unused bandwidth is wasteful because it could be used for other traffic that may need it. Utilization is formally defined as The percent of total available capacity in use. Capacity being the total data carrying capability of a circuit or network in bits per second.
The cost associated with high-speed circuits is too great to allow them to go unused. Optimum network utilization occurs for Ethernet under 37%. After this point the network is too saturated with communications and token passing methods out perform CSMA/CD (Carrier Sensed Multiple Access with Collision Detection). For token passing methods utilization can approach upwards of 70%. WAN links, such as those used for VoIP, should be operating at about 70% utilization before considering an upgrade. Technical Overview Mixed Media Requirements In a nutshell: DATA accurate not timely VOICE timely not accurate Delay The level of service that users expect, when making a phone call, is extremely high.
It has been found that if users experience as little as 500ms round trip delay, they consider it a problem. Consider the graph below from the Voice and Data Handbook, 1999. Problems are few until delay goes beyond 300ms and becomes a concern at about 500-600ms. kilometers per millisecond. Also part of propagation time is the delay caused by putting data onto the media.
Its dependent upon the data volume and the speed of the line but consider for example to put a 1,024 byte packet onto a T1 line it would take about 5 milliseconds. The delay we do have controller over is rightfully called, variable. The type of routers chosen, even the protocols used, the speed of the media; all of these are variable delays. It is important to consider the all aspects of your network design. Increasing performance by reducing delay can be much more cost effective than simply adding more circuits.
Packet Loss Packet loss is exactly how it sounds; packets are dropped for one reason or another. Its not so important for Voice over IP because of built in codecs to compensate for up to 10% loss. Fax, however, is inherently more sensitive to both delay and packet loss. The quality of links should be evaluated along with source and destination hardware. If media is not of sufficient speed or reliability consider upgrading to ensure throughput.
Jitter Jitter isnt much of an issue with data communications but for voice you could get the wrong idea if someone said, gone the people have, when they meant, have the people gone? Jitter occurs when packets arrive at the destination out of order. Packets can be numbered, taken into a buffer and released at the same time. This obviously contributes to delay but if jitter is occurring sufficient bandwidth must exist. Network Technology Voice over ATM There are basically two models for integrating voice and data transport and translate Transport is the transparent support of voice over the existing network. Simulation of tie lines over ATM using circuit emulation is a good example.
Translate is the translation of traditional voice functions by the data infrastructure. An example is the interpretation of voice signaling and the creation of switched virtual circuits (SVCs) within ATM Internetworking Technologies Handbook, Second Edition. Whenever you speak of the network technologies involved with transporting simultaneous voice and data, you must choose from the few that are scalable and fast enough to handle …