Characteristics of communication links

Skills: none

IT concepts: data transmission rate, latency, jitter, packet loss, medium

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Characteristics of communication links

• Internet concepts– Applications– Technology (connectivity)– Implications for

• Individuals• Organizations• Society

• Internet skills– Application development– Content creation

• Text• Image• Audio• Video

Link characteristics

1. Speed

2. Latency

3. Jitter

4. Packet loss rate

5. Medium

Do you know the speed of the link between your home and your ISP?

LAN router

ISP router

Home LAN

The Internet

What is the unit of measure for data transmission speed?

Measure of Example units Rate ratio

Distance Inches, miles, light years

Rate of movement Miles/hour, inches/year

Distance/time

Weight Ounces, tons, grams

Amount of data Bits, bytes, gigabytes

Rate of data transmission

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What is the unit of measure for data transmission speed?

Measure of Example units Rate ratio

Distance Inches, miles, light years

Rate of movement Miles/hour, inches/year

Distance/time

Weight Ounces, tons, grams

Amount of data Bits, bytes, gigabytes

Rate of data transmission

Bits/second, bytes/second, gigabits/second

Amount of data/time

Plan Speed down Speed up Price

Starter DSL 1 Mbps 384 Kbps $19.99

Power DSL 3 Mbps 768 Kbps $29.99

Turbo DSL 7.1 Mbps 768 Kbps $42.99

FIOS fast 15 Mbps 5 Mbps $49.99

FIOS faster 25 Mbps 15 Mbps $64.99

FIOS fastest 50 Mbps 20 Mbps $144.99

Verizon Internet plans, November 2009

Note that speeds are “up to” these rates.

Note the asymmetry in upload and download speed.

Prefixes for large quantities

Prefix Exact Close enough Name

Kilo 1,024 1,000 Thousand

Mega 1,024^2 1,000,000 Million

Giga 1,024^3 1,000,000,000 Billion

Tera 1,024^4 1,000,000,000,000 Trillion

Peta 1,024^5 1,000,000,000,000,000 Quadrillion

After these prefixes come exa, zetta and yotta. The pattern continues -- each is 1,024 times the previous one.

Availability of 100 Mbps service in 2009

Follow this link for 100 Mbps cost.

Latency – the time for the first packet to arrive

About half the ping (round trip) time

Jitter – variation in latency

Ping time and jitter from Los Angeles

Distance(miles)

P1(ms)

P2(ms)

P3(ms)

P4(ms)

Avg.(ms)

Jitter(st dev)

SantiagoChile 5,585 412 346 228 225 303 92.08

OxfordEngland 5,408 195 194 195 193 194 .96

Packet loss rate

No packets lost -- packet loss is rare, but occurs

Packet loss rate from SLAC (Palo Alto, CA)

•Steady improvement everywhere but Africa•All regions but Africa an parts of Asia are now under 1%

Current year data on Verizon backbone latency, packet loss rate and jitter

http://www.verizonbusiness.com/about/network/latency/

Transfer rate from SLAC (Palo Alto, CA)

Copper, twisted pair

Copper, coaxial cable

Fiber

Terrestrial radio

Satellite radio

Link medium

We just covered five characteristics of a communication link. Do you recall what they were?