Bandwidth in the Local and Wide Area Network

Monmouth County Vocational Schools / Advanced Networking Program

X.25

ATM

56k SONETT1/T3

OC 192

Gigabit

Megabit

William Portilla

What is Bandwidth ?

The amount of data that can be transmitted in a fixed amount of time.

For digital devices, the bandwidth is usually expressed in bits per second(bps) or bytes per second(Bps). For analog devices, the bandwidth is expressed in cycles per second, or Hertz (Hz)

Terms Used to Measure Bandwidth

- Shown in decimaldeka (da) = 10 ^ 1 = 10 tenhekto (h) = 10 ^ 2 = 100 hundredkilo (k) = 10 ^ 3 = 1,000 thousandmega (M) = 10 ^ 6 = 1,000,000 milliongiga (G) = 10 ^ 9 = 1,000,000,000 billiontera (T) = 10 ^ 12 = 1,000,000,000,000 trillionpeta (P) = 10 ^ 15 = 1,000,000,000,000,000quadrillionexa (E) = 10 ^ 18 = 1,000,000,000,000,000,000 quintillionzetta (Z) = 10 ^ 21 =1,000,000,000,000,000,000,000 sextillionyotta (Y) = 10 ^ 24 = 1,000,000,000,000,000,000,000,000 septillion (eg. Zb – zetta bits/sec ZB – zetta bytes/sec)

Data Transmission Bandwidth Measurement

The bandwidth or data-carrying capacity of a channel such as a network cable, a modem, or a phone line is commonly measured in bits persecond.

kilobit (kb) = 1,000 bitsKilobit (Kb) = 1,024 bitsbps = bits per secondkbps = kilobits (1000 bits) per second (decimal)Kbps = Kilobits (1024 bits) per second (binary)kBps = kilobytes (1000 bytes) per secondKBps = Kilobytes (1024 bytes) per secondMbps = megabits (1,000,000 bits) per second (decimal)Mbps = megabits (1,048,576 bits) per second (binary)MBps = megabytes (1,000,000 bytes) per second (decimal)MBps = megabytes (1,048,576 bytes) per second (binary)

LAN Bandwidth

Local Area Networks supply bandwidth based upon their physical and data link layer properties:

Token Ring - 4/16/100 Mbps10Base T - 10 Mbps

100Base T - 100 Mbps (fast Ethernet)

FDDI – 100 Mbps (campus backbone)Gigabit Ethernet - 1,000 Gbps

ATM - 150kbs to 600kbs (high QOS)

WAN Bandwidth

Wan connections are comprised of several types of technologies each with its' own unique interface and transfer rate. A WAN uses the Physical and Data link layers to define Bandwidth.

• ASYNCHRONOUS CONNECTIONS - 56k modem • SYNCHRONOUS CONNECTIONS - DSU/CSU - T1/T3

lines - T1= 1.54mbps / T3 = 44.7 mbps (28 T1’s)• ISDN - (2) 64kbps channels - aggregate 128kbs - and higher

by combining ISDN lines (video conferencing)• X.25 -The ITT standard for connecting terminal equipment

to packet switching data circuits. Max effective speed 2mbps• FRAME RELAY - can offers users transmission speeds of

2.048 megabits per second and higher. It allows faster speeds than the X.25 packet switching standard.

WAN Bandwidth(cont.)

– SONET - Synchronous Optical Network, a standard for connecting fiber-optic transmission systems with speeds ranging from 51.8 Mbps (about the same as a T-3 line) to 2.48 Gbps. for Optical Carrier, used to specify the speed of fiber optic networks conforming to the SONET standard. The table shows the speeds for common OC levels.

– OC = SpeedOC-1 = 51.85 MbpsOC-3 = 155.52 MbpsOC-12 = 622.08 MbpsOC-24 = 1.244 GbpsOC-48 = 2.488 GbpsOC-192=9.952 Gbps

ATM- Asynchronous Transfer Mode. A method of communications in which information is transmitted in "cells". Transmission rates from 150 megabits per second to 600 mbps.

When Data Pipes of Unequal Bandwidths Encounter One Another

Network traffic gets in trouble primarily when a high-speed segment meets a low-speed segment. IP was designed to run over links with low throughput rates-low by today's standards, that is. The variation between the slowest links and the fastest ones was once 110 bits/sec and 2,400 bits/sec-a ratio of slightly more than 20 to 1. Compare that ratio with one you might observe on a typical router configuration today: A router with a 56Kbit/sec frame relay interface and a 100Mbit/sec LAN interface has a ratio of approximately 2,000 to 1. The same router with a 1Gbit/sec LAN interface has a ratio of 20,000 to 1. If a thin pipe fills up and a fat pipe full of traffic is destined for the slow interface, the only thing the router can do is start throwing packets away or putting them into a buffer or queue. If the throughput mismatch is large, the buffers had better be large.

Multiplexing to Increase Bandwidth

A multiplexer optimizes the use of communications facilities by configuring and bringing together many channels for efficient transmission on a network.

Fiber Optic Multiplexer manufacturers can increase the capacity of a single fiber 400 fold by multiplexing multiple wavelengths over a single fiber.