Migrating To High-speed LANs

Corporate LANs are facing explosive

growth in traffic, driving the need for higher and higher bandwidths. A number of

technologies are available for increasing the speed and bandwidth of these LANs. However,

a number of factors have to be considered to decide on the technology option as well as

implementation of the same. Some of these are: type of application and data, size of data,

impact on the network bandwidth, network performance requirements, cost, reliability,

flexibility for upgrading in phases, scalability for future growth, and availability of

tools for management and support.

An understanding of the applications that

are driving the need for a higher bandwidth play a critical role in planning and

implementing network upgrades. Any upgrade without a proper analysis of these factors

would not yield the desired results, leading to wasted investments. Following are the

applications driving the need for higher bandwidths:

SCIENTIFIC MODELING AND

ENGINEERING: These applications involve 3D modeling/visualization of scientific

or complex objects. They often require creation and transfer of data files of the sizes of

100 MB to 100 GB. They need higher bandwidth for desktop, server, and backbone.

PUBLICATIONS, MEDICAL DATA

TRANSFER: Magazines, brochures, and other full-color publications created on the

desktop are often transmitted directly to the printing centers. Similarly, many medical

applications involve transfer of complex images over network between hospitals/doctors/

and clinical/diagnostic centers. These files are also of GB sizes and require higher

bandwidth for desktops, servers, and backbone.

INTRANET/INTERNET APPLICATIONS:

Many enterprises are building private intranets and deploying applications that go beyond

email involving static information publishing/dissemination, groupware, workflow, and 2/3

tier client server applications on the intranets. The information exchanged for these

applications would be compound documents comprising data, text, audio, video, and images.

The browser would be the universal user interface from which any information from anywhere

in the corporate network can be accessed from the desktop.

Large files of 1 MB to 100 MB typically get

transferred in real-life transactions that take place on corporate intranets. These online

transaction applications have different type of networking needs. In addition to high

network bandwidth, they need faster transfer rates and low transmission latency.

DATAWAREHOUSING: The

datawarehousing applications for business intelligence often involve extraction and

transfer of Giga to Terrabytes of data from the operational databases from all over the

enterprise to the central datawarehouse database. The extracted information in the

warehouse is often accessed by thousands of users. There is also a need to constantly

update the databases to provide users near-real-time data for critical business analysis

and decisions. These applications need low latency for faster search and access to data

and higher bandwidth for servers and backbones.

NETWORK BACKUP: In

enterprises, backup of servers and storage systems is often done for archival purposes.

Such backups are usually taken after office hours and require large amounts of bandwidth

during a fixed amount of time. The backup involves GBs or Terrabytes of data distributed

over hundreds of servers and storage systems throughout an enterprise. These applications

require higher bandwidth for servers and backbone, and low latency.

DESKTOP VIDEO: There is

going to be an increase in the desktop applications involving video e.g.

videoconferencing, education/training etc. These typically involve datastream transfers at

1.5-3.5 Mbps at the desktops. They not only need higher bandwidth for servers and

backbones but also need low and predictable latency.

These are the various types of emerging

applications that are driving the need for high-performance networks. We have also found

that each type of application has a different type of requirement.

Selecting Technology



In addition to understanding the application requirements one also needs to keep in view
the following common issues while planning a network upgrade.

Any upgradation to higher speed should

ideally be done transparently to the current users without disrupting their work. Also,

depending on the application''s need and types of data, sizes of data etc., the individual

segments have to be taken up for upgradation. For instance, backbone upgrades,

desktop-to-switch upgradation, switch-to-server upgradation etc.

Technology should be properly chosen while

optimizing the investments already made in the current networks. Technology selected

should offer scalability to take care of future growth. Cost of ownership is a major

factor for network administrators. Here, the one-time purchase cost as well as ongoing

support for training and maintenance tools need to be taken into account. Network

reliability is very crucial to the success of an enterprise. The network topology and the

internetworking schemes should be so chosen that the ultimate network built becomes highly

reliable.

The most important of the criteria is the

flexibility to handle new type of applications and data. Increasingly, the emerging

applications need the network to handle various type of data comprising audio, text, data

image, and video. The loading and traffic patterns may also vary according to the

application. The network technology should have capabilities to handle these requirements.

Lastly, availability of tools for support

and management is critical. Whether the upgrade needs a different set of tools for support

and maintenance or whether the existing tools would be adequate, needs to be examined. For

new technologies their availability itself may be an issue.

High-speed Network Technologies



Above mentioned was the new applications that are driving the need to high speed
networking and the criteria for choosing a proper technology. Here are the various

technology options for high-speed networking.

GIGABIT ETHERNET: Gigabit

Ethernet is an extension to the highly successful 10 Mbps and 100 Mbps IEE 802-3 Ethernet

standards offering a raw bandwidth of 1000 Mbps. It supports new full duplex operation

modes for switch-to-switch and switch-to-end station connection and half duplex operating

modes for shared connections, using repeaters and the CSM/CD access method.

Initially, operational over optical fiber,

Gigabit Ethernet would also use category 5 Unshielded Twisted Pair (UTP) cabling and Coax.

It can be switched, routed, or shared depending upon cost and bandwidth requirements.

ATM: Asynchronous Transfer

Mode (ATM) technology has been developed to provide scalable high-speed networking for

both data and voice. Starting with speeds of 150 Mbps it can be scaled for a speed of up

to 622 Mbps. It can support a wide range of data services including standard voice

telephony, TDM network trunks, compressed voice and video, connection-oriented datacom

protocols such as Frame relay, TCP, SNA, and X.25. It also supports connectionless

datagram-based communication protocols.

ATM networks can be built by connecting

devices to an ATM switch. Simple networks might be star configured with one multi-ported

ATM switch at the center of the star. Larger ATM networks are tree-structured with an ATM

switch at each branch. The following table gives a summary of ATM and Gigabit features:

A comparison of the two technologies i.e.

ATM and Gigabit Ethernet reveals that ATM is advantageous in terms of scalability,

guaranteed quality of service (at hardware level), fault tolerance, and availability of

products from multiple vendors in the market. However, it is expensive, complex in

technology, and requires retraining of staff. Standards are also still in the evolving

stage. The Gigabit Ethernet is relatively inexpensive and compatible with existing

Ethernet tools management. However, Gigabit Ethernet does not offer quality service

support at hardware level. It requires new switching and routing hardware, and has severe

distance limitations over copper and shared nets. Its standards will also not be ready

till March 1998.

These two technologies are similar in some

ways and different in others. They have to be viewed as complementary rather than

competing technologies. In terms of speed required to eliminate backbone congestion, any

one of them can be chosen. They differ mainly in terms of applications. ATM is designed to

support multimedia traffic and is best technology to support time-sensitive data, voice,

and video. Moreover, ATM provides a seamless connection of LAN and WAN without protocol

conversion. A major shortcoming of ATM is its high cost. This is mainly due to its quality

of service guarantees and advanced congestion control features.

Gigabit Ethernet maintains full

compatibility with the huge installed base of Ethernet networks. The current investment in

management and maintenance tools can be fully leveraged. It is simple to connect the

existing low-speed Ethernet users and devices using LAN switches or routers. As the frame

format and sizes are same for Ethernet technologies, no other network changes are

necessary. As far as high-speed LANs are concerned, the choice between ATM and Gigabit

Ethernet has to be based on the factors described above.

Network Migration



After choosing the proper technology, the actual migration has to be planned keeping in
mind the application need and traffic patterns. The most likely user upgrade scenarios

would be:

Depending on the application need, a phased

upgrade program can be taken up for specific segments of the enterprise network.

The emerging applications are creating

incredible growth of traffic on corporate LANs, driving the need for high-speed,

high-bandwidth LANs. We need to consider the nature of the application, the data type and

volumes, cost, reliability, disruption, maintenance tools, and TCO factors before deciding

about the technology.

The two technologies-ATM and Gigabit

Ethernet-offer complementary features and hence the user need to select either one of them

or a combination depending on his need. Finally a phased approach need to be taken for

upgrading the network segments gain depending on the requirements.

Dr AL RAO,



Group VP, IS, (Software Quality & Technology)


Wipro Infotech.