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CSc 450/550Computer Networks

Communication Technologies

Jianping Pan

Summer 2007

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Last lectures

• Guest lectures on UVicNet, BCNet, CA*Net4

• Introduction– brief Internet history– current Internet structures

• end-user's point of view• service-provider's point of view• network-protocol's point of view

– how's your traceroute to google.com?• ever tried traceroute servers?

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Feedback on A0

• More “networks” courses– Advanced Computer Networks– Advanced Communication Networks– Wireless and Mobile Networks– multimedia networking in Multimedia Systems– network computing in Distributed Systems– Network Security and Testing– this course helps you build a foundation for them

• lab hours conflict? a smaller classroom?

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Discussion board

• Get help and help others– http://groups.google.com/group/csc450

• Ways to get help– most importantly, attend lectures and labs– use Google group as much as possible– write to lecture/lab instructors– meet during course office hours– arrange for extra help

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Today's topic

• Communication technologies– goal: to understand the basic communication

technologies underneath the Internet• Internet access, from home or at work• Internet backbone, big pipes• a little bit EE-flavored

– networking is jointly pursed by both EE and CS

– network acronyms (you will see a lot of them!)• http://www.cisco.com/univercd/cc/td/doc/cisintwk/ita/index.htm

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Internet access: phone line

• Analog dialup– computer w/ ISA, PCI, serial, USB– modem w/ RJ11– telephone line

• unshielded twisted pair (UTP) or flat

– up to 56Kbps downstream

• Digital access– ISDN: 2x64Kbps (2B+D)

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More on modems

• Nyquist limit (noiseless channel)– 2 H log2 V bps

• Shannon limit (noisy channel)– H log2 (1+S/N) bps

• analog local loop: H=3000~4000Hz; S/N=30dB

• Bandwidth, sample, symbol, bit, data rate– (bits / symbol) * (symbols / second) = bps

• baud rate: 2400; data rate: 9.6, 19.2, 28.8, 33.6Kbps

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9.6Kbps 14.4Kbps

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• 56Kbps?– increased S/N, asymmetric H

Dialup ISPs

A/DD/A

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Digital subscriber lines

• Asymmetric DSL (ADSL)– free up more H– frequency division multiplexing (FDM)

• or discrete multi-tone (DMT)• telephone: filter for regular phones• upstream: small bandwidth• downstream: larger bandwidth

– DSL modem• Ethernet or USB connection to computer/router

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DSL vs dialup

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DSL ISPs

• Splitter or (micro) filter?

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Internet access: cable line

• Traditionally, cable TV is 1-way broadcast– one-way amplifier– shared coaxial cable

• Internet access through HFC (DOCSIS)– two-way communication channels

• small upstream bandwidth• larger downstream bandwidth

– smaller (shared) cable segment• security

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HFC ISPs

• Cable vs DSL

hybrid fiber-coaxial

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Internet access: LAN

• UVicNet: 10/100Mbps switched Ethernet– RJ45

• old days: AUI, BNC w/ coaxial, shared

– UTP Cat3: 10Mbps– UTP Cat5: 100Mbps

• more twists per inch

• ResNet: 10Mbps switched– was 10Mbps shared

BNC

AUI

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Internet access: WLAN

• WiFi (e.g., UVic AirNet)– 802.11b: 2.4GHz, 100ft@11Mbps

• direct sequence spread spectrum• 11 overlapping channels• channel 1, 6, 11 independent

– 802.11a: 5GHz, 54Mbps• orthogonal frequency division multiplexing

– 802.11g: 2.4GHz, 54Mbps

• Security

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Internet access: WMAN

• Wireless MAN (metropolitan area network)– MMDS: 198MHz@2.5GHz

• range: 25~50km; 3Mbps downstream 200Kbps up

– LMDS: 1.3GHz@28~31GHz• range: 2~5km, line-of-sight!• wireless DSL: 36Gbps downstream 1Mbps up/sector

• IEEE 802.16: WiMax– 10~66GHz (802.11a: 2-11GHz NLOS), OFDM

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Wireless*AN

• Personal area network (802.15)– range: up to 10m– Bluetooth (802.15.1): 1Mbps; headset-to-phone– UWB (802.15.3): 400Mbps; wireless USB

• Local area network (802.11)– range: up to 100m

• Metropolitan area network (802.16)– range: up to 50km

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Internet access: cellular networks

• Cellular systems– 1st generation (80’s): analog voice (9.6Kbps)

• AMPS: cells, frequency reuse, cell split; FDMA• base station, mobile switching center, handoff

– 2G (90’s): digital voice (14.4Kbps)• TDMA, GSM, CDMA• 2.5G (~100Kbps): GPRS, EDGE, EV-DO, EV-DV

– 3G: digital voice and data (384Kbps, 2Mbps)• WCDMA, CDMA2000, TD-SCDMA

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Internet backbone: big pipes!

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Fiber optics

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Multiplexing technologies

• Frequency division multiplexing (FDM)

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Wavelength division multiplexing

WDM

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Time division multiplexing

TDM

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• Satellite vs fiber

Communication satellite

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Internet backbone evolution

• IP/ATM/SONET/WDM– IP: datagram– ATM: virtual circuit– SONET: circuit switching– WDM: lights in different color

• IP/SONET/WDM• IP/WDM

– newest technology

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Internet backbone structures

• Tier-1– ATT– Sprint– MCI

• Tier-2– regional

• Tier-3– local

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier-2 ISPTier-2 ISP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

localISPlocal

ISPlocalISP

localISP

localISP Tier 3

ISP

localISP

localISP

localISP

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UVicNeta small “Internet”

VLAN Y VLAN Y

C3550 C3550

C5500w. RSM

C5500w. RSM

C5500w. RSM

C5500w. RSM

CoreC6509

VLAN X

CoreC6509

VLAN X

Traffic Shaping

BCNet -Primary Path forResearch Traffic

BCNet -Primary Path for

Commodity Traffic

General Departmental VLANs

Legacy Protocols ONLYEIGRP (IPX & Appletalk)

IP ONLY OSPF Area 0

ResNet

EdgeRouter

EdgeRouter

100 FX

Gig E

EngrNet

Gig E – Primary Path

Gig E – Fallback Path

Fast E – Primary Path

Fast E – Fallback Path

C6509C6509

Public Access Network(PAN) VLANs

C6509

IntrusionPrevention

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Link characteristics• Speed (bandwidth): bit-per-second• Delay: millisecond

– transmission delay: packet length / link speed– propagation delay: travel distance / signal speed– processing delay– queuing delay: the most complicated one

A

B

propagation

transmission

nodalprocessing queueing

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• Loss: percentage– transmission error– congestion loss

• router buffer–packets enqueue when output is busy–packet dequeue when output is idle

• if buffer is full–some packets have to be dropped

More on link characteristics

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This lecture

• Internet communication technologies– Internet access

• phoneline: how to go faster on the same twisted pair?• cableline, Ethernet, wireless*AN, cellular, etc

– Internet backbone• multiplexing technologies: FDM, WDM, TDM

• Explore further– your home Internet access (bandwidth, latency)– compare with your friends' (reliability)

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One more message...

• Considering graduate school?– there is a lot of financial support you can use!

• needs-based, merits-based, ...– NSERC Postgraduate Scholarship (PGS)

• Canada Graduate Scholarship (CGS)– Provincial Government of BC

• 2,500 more graduate seats in three years• new Pacific Century Graduate Scholarship!

– UVic Fellowship– Teaching Assistantship, Research Assistantship

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Next lectures

• Network architecture• Client-server model• HTTP