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Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Brief Bio

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Chapter 1 roadmap l.jpg
Chapter 1: roadmap

1.1 What is the Internet?

1.2 Network edge

1.3 Network core

1.4 Network access and physical media

1.5 Internet structure and ISPs

1.6 Delay & loss in packet-switched networks

1.7 Protocol layers, service models

1.8 History

1: Introduction


Brief bio l.jpg
Brief Bio

  • IBM (10 years): Programmer/manager AIX base operating system, manager of LAN (PCLP, PCNP) and PC/3270 software development

  • Dell Computer Corporation (4 years): manager software (firmware) development, V P of PC Products group

  • VTEL (4 years): senior VP development and general manager

  • eOn Communications (3 years): President & CEO

  • Bynari Inc (1 year): Chairman & CEO

  • UTA Faculty since Summer 2001

1: Introduction


My hobby and preferred mode of transportation l.jpg
My Hobby… and preferred mode of transportation

1: Introduction


The network edge l.jpg

end systems (hosts):

run application programs

e.g., WWW, email

at “edge of network”

client/server model

client host requests, receives service from server

e.g., WWW client (browser)/ Web server; email client/mail server

peer-peer model:

host interaction symmetric

e.g.: teleconferencing, groupware, file sharing

“connection”

The network edge:

1: Introduction


Network edge connection oriented service l.jpg

Goal: data transfer between end sys.

handshaking: setup (prepare for) data transfer ahead of time

Hello, hello back human protocol

set up “state” in two communicating hosts

TCP - Transmission Control Protocol

Internet’s connection-oriented service

TCP service[RFC 793]

reliable, in-order byte-stream data transfer

loss: acknowledgements and retransmissions

flow control:

sender won’t overwhelm receiver

congestion control:

senders “slow down sending rate” when network congested

The Internet's

Connection-Oriented

Service

Network edge: connection-oriented service

1: Introduction


Network edge connectionless service l.jpg

Goal: data transfer between end systems

same as before!

UDP - User Datagram Protocol [RFC 768]: Internet’s connectionless service

unreliable data transfer

no flow control

no congestion control

App’s using TCP:

HTTP (WWW), FTP (file transfer), Telnet (remote terminal/login), SMTP (email)

App’s using UDP:

streaming media, teleconferencing, Internet telephony

Network edge: connectionless service

1: Introduction


Chapter 1 roadmap7 l.jpg
Chapter 1: roadmap

1.1 What is the Internet?

1.2 Network edge

1.3 Network core

1.4 Network access and physical media

1.5 Internet structure and ISPs

1.6 Delay & loss in packet-switched networks

1.7 Protocol layers, service models

1.8 History

1: Introduction


The network core l.jpg

mesh of interconnected routers/switches

the fundamental problem for the core: how to get data through an internet (network layer switching)?

circuit switching: dedicated circuit per call, e.g. telephone network

packet-switching: data sent thru net in discrete “chunks”, e.g. ??

The Network Core

1: Introduction


Network core circuit switching l.jpg

End-end resources reserved for “call”

link bandwidth, switch capacity, queues/buffers

dedicated resources: no sharing

dedicated circuit-like (guaranteed) performance

call setup required

Network Core: Circuit Switching

1: Introduction


Network core circuit switching10 l.jpg

network resources (e.g., bandwidth) divided into “pieces”

pieces allocated to calls

resource piece idle if not used by owning call (no sharing)

dividing link bandwidth into “pieces”

frequency division (FDM)

time division (TDM)

FDM:

1

2

3

4

frequency

time

TDM:

frequency

time

Network Core: Circuit Switching

1: Introduction


Network core circuit switching tdm example l.jpg

T1 Circuit

1.536 Mbps bandwidth, 24 time “slots”

500msec setup time

Yields:

1.536Mbps/24 =

64Kbps per slot or “circuit”

How long to send:

80KByte file?

1MByte file?

Network Core: Circuit Switching TDM Example

(80 * 103 * 8) / (64 * 103 ) = 640/64 = 10 (+ 0.5 sec = 10.5 sec)

(1 * 106 * 8 ) / (64 * 103 ) = 8000/64 = 125 (+ 0.5 sec = 125.5 sec)

1: Introduction


Network core packet switching l.jpg

each end-end data stream divided into packets

users A & B packets share network resources

each packet uses full link bandwidth

resources used as needed,

Bandwidth division into “pieces”

Dedicated allocation

Resource reservation

Network Core: Packet Switching

resource contention:

  • aggregate resource demand can exceed amount available

  • congestion: packets queue, wait for link use

  • store and forward: packets move one hop at a time

    • transmit over link

    • wait turn at next link

1: Introduction


Network core packet switching13 l.jpg

Packet-switching versus circuit switching: human restaurant analogy

other human analogies?

D

E

Network Core: Packet Switching

10 Mbps

Ethernet

C

A

statistical multiplexing

1.536 Mbps

B

45 Mbps

queue of packets

waiting for output

link

1: Introduction


Packet switching store and forward l.jpg

Takes L/R seconds to transmit (push out) packet of L bits onto link or R bps

Entire packet must arrive at router before it can be transmitted on next link: store and forward

delaytrans = 3L/R

Example:

L = 7.5 Mbits

R = 1.5 Mbps

delay (transmission) = 15 sec

“message” switching

vs.

“packet” switching

Packet-switching: store-and-forward

L

R

R

R

1: Introduction


Packet switching message segmenting l.jpg

Now break up the message into 5000 packets onto link or R bps

Packet Switching: Message Segmenting

  • Each packet 1,500 bits

  • 1 msec to transmit each packet on one link

  • pipelining: each link works in parallel

  • Delaytrans reduced from 15 sec to 5.002 sec

1: Introduction


Packet switching versus circuit switching l.jpg

1 Mbps link onto link or R bps

each user:

generates traffic at 100Kbps when “active”

is active 10% of time

Capacity:

circuit-switching:

10 users

packet switching:

with 35 users, probability > 10 active less than .0004

Packet switching allows more users to use (i.e. “share) the network!

Packet switching versus circuit switching

N users

1 Mbps link

1: Introduction


Packet switching versus circuit switching17 l.jpg

Great for onto link or R bpsbursty data

resource sharing

no call setup

Excessive congestion (load): packet delay and loss

protocols needed for reliable data transfer, congestion control

Q: How to provide circuit-like behavior?

bandwidth guarantees needed for audio/video and real-time applications

in practice, solutions still evolving (chapter 6)

Is packet switching a “slam dunk winner?”

Packet switching versus circuit switching

1: Introduction


Packet switched networks routing forwarding l.jpg

Goal: onto link or R bps move packets through routers from the source (router) to the destination (router)

we’ll study several path selection algorithms (chapter 4)

datagram network:

destination address determines next hop

routes may change during session

analogy: driving, asking directions

virtual circuit network:

each packet carries tag (virtual circuit ID), tag determines next hop

fixed path determined at call setup time, remains fixed thru call

routers/switches maintain per-call state

Packet-switched networks: routing/forwarding

1: Introduction


Network taxonomy l.jpg

Packet-switched onto link or R bps

networks

Circuit-switched

networks

FDM

TDM

Datagram

Networks

Networks

with VCs

Network Taxonomy

Telecommunication

networks

  • A datagram network is not either connection-oriented or connectionless (i.e., it can be both).

  • The Internet provides both connection-oriented (TCP) and connectionless services (UDP) to apps.

1: Introduction


Chapter 1 roadmap20 l.jpg
Chapter 1: roadmap onto link or R bps

1.1 What is the Internet?

1.2 Network edge

1.3 Network core

1.4 Network access and physical media

1.5 Internet structure and ISPs

1.6 Delay & loss in packet-switched networks

1.7 Protocol layers, service models

1.8 History

1: Introduction


Access networks and physical media l.jpg

Q: How to connect end systems to edge router? onto link or R bps

residential access nets

institutional access networks (school, company, organization)

mobile access networks

Key considerations:

bandwidth (bits per second) of access network?

shared or dedicated?

Access networks and physical media

1: Introduction


Residential access point to point access l.jpg

Dialup via modem (PPP) onto link or R bps

up to 56Kbps direct access to router (conceptually, often less)

not “always on”

still most prevalent access means

ADSL: asymmetrical digital subscriber line

up to 1 Mbps home-to-ISP router (typically < 256 Kbps)

up to 8 Mbps ISP router-to-home (typically < 1.5 Mbps)

Uses FDM with 3 contiguous frequency bands

downstream channel: 50 kHz – 1 MHz band

upstream channel: 4 kHz – 50 kHz band

telephone channel: 0 – 4 kHz band

ADSL deployment: rapidly evolving

Residential access: point to point access

1: Introduction


Residential access cable modems l.jpg

HFC: hybrid fiber coax (cable) onto link or R bps

asymmetric: up to 10Mbps downstream, 1 Mbps upstream

requires cable modem at access point

network of cable and fiber attaches homes to ISP router

shared access to router among homes

issues: congestion, dimensioning

deployment: widely available via cable companies, e.g., AT&T(Comcast), AOL Time- Warner, Charter, etc.

Residential access: cable modems

1: Introduction


Residential access cable modems24 l.jpg

Shared broadcast medium onto link or R bps

Residential access: cable modems

Now, OC-192

Diagram: http://www.cabledatacomnews.com/cmic/diagram.html

1: Introduction


Cable network architecture overview l.jpg
Cable Network Architecture: Overview onto link or R bps

Typically 500 to 5,000 homes

cable headend

home

cable distribution

network (simplified)

1: Introduction


Cable network architecture overview26 l.jpg
Cable Network Architecture: Overview onto link or R bps

cable headend

home

cable distribution

network (simplified)

1: Introduction


Cable network architecture overview27 l.jpg

server(s) onto link or R bps

Cable Network Architecture: Overview

cable headend

home

cable distribution

network

1: Introduction


Cable network architecture overview28 l.jpg

C onto link or R bps

O

N

T

R

O

L

D

A

T

A

D

A

T

A

V

I

D

E

O

V

I

D

E

O

V

I

D

E

O

V

I

D

E

O

V

I

D

E

O

V

I

D

E

O

5

6

7

8

9

1

2

3

4

Channels

Cable Network Architecture: Overview

FDM:

cable headend

home

cable distribution

network

1: Introduction


Institutional access local area networks l.jpg

company/univ. onto link or R bpslocal area network (LAN) connects end system to edge router

Ethernet:

shared or dedicated cable connects end system and router

10 Mbps, 100Mbps, Gigabit Ethernet

deployment: institutions, home LANs

LANs: chapter 5

Institutional access: local area networks

1: Introduction


Wireless access networks l.jpg

shared onto link or R bpswireless access network connects end system to router

wireless LANs:

radio spectrum (unlicensed band) replaces wire

e.g., Linksys 802.11g

wider-area wireless access (MAN/WAN)

CDPD: wireless access to ISP router via cellular network

3G/EV-DO, GSM, WAP

WiMax/IEEE 802.16

router

base

station

mobile

hosts

Wireless access networks

1: Introduction


Home networks l.jpg

Typical home network components: onto link or R bps

ADSL or cable modem

router/firewall/NAT

Ethernet

wireless access

point

Home networks

wireless

laptops

to/from

cable

headend

cable

modem

router/

firewall

wireless

access

point

Ethernet

(switched)

1: Introduction


Physical media l.jpg

physical link: onto link or R bps transmitted data bit propagates across link

guided media:

signals propagate in solid media: copper, fiber

unguided media:

signals propagate freely, e.g., RF, IR

Twisted Pair (TP)

two insulated copper wires

Category 3: traditional phone wires, 10 Mbps Ethernet

Category 5 TP: 10/100/1000Mbps Ethernet

Category 6 TP now standard: Up to 650 Mbps

Physical Media

1: Introduction


Physical media coax fiber l.jpg

Coaxial cable: onto link or R bps

wire (signal carrier) within a wire (shield)

baseband: single channel on cable

broadband: multiple channel on cable

bi-directional

use in 10Mbs Ethernet (10Base2) and cable networks

Physical Media: coax, fiber

Fiber optic cable:

  • glass fiber carrying light pulses

  • high-speed operation:

    • 100Mbps Ethernet

    • high-speed point-to-point transmission (e.g., 5 Gbps)

  • low error rate

1: Introduction


Physical media radio l.jpg

signal carried in electromagnetic spectrum onto link or R bps

no physical “wire”

bi-directional

propagation environment effects:

reflection

obstruction by objects

interference

Physical media: radio

Radio link types:

  • terrestrial microwave

    • e.g. up to 45 Mbps channels

  • LAN (e.g., AirConnect)

    • 2Mbps, 11Mbps (802.11b)

    • 50+ Mbps (802.11a/g)

  • wide-area (e.g., cellular)

    • e.g. CDPD, 10’s Kbps

  • satellite

    • up to 50Mbps channel (or multiple smaller channels)

    • 270 msec end-end delay

    • geosynchronous versus LEOS

1: Introduction


Chapter 1 roadmap35 l.jpg
Chapter 1: roadmap onto link or R bps

1.1 What is the Internet?

1.2 Network edge

1.3 Network core

1.4 Network access and physical media

1.5 Internet structure and ISPs

1.6 Delay & loss in packet-switched networks

1.7 Protocol layers, service models

1.8 History

1: Introduction


Internet structure network of networks l.jpg

roughly hierarchical onto link or R bps

at center: “tier-1” ISPs (e.g., Sprint, AT&T, MCI, Level3, Qwest, Cable & Wireless),

national/international coverage

treat each other as equals

NAP

Tier-1 providers also interconnect at public network access points (NAPs/MAEs)

Tier-1 providers interconnect (peer) privately

Internet structure: network of networks

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

1: Introduction


Tier 1 isp e g sprint l.jpg
Tier-1 ISP: e.g., Sprint onto link or R bps

Sprint US backbone network

1: Introduction


Tier 1 isp e g mci l.jpg
Tier-1 ISP: e.g., MCI onto link or R bps

MCI U.S. backbone network

1: Introduction


Tier 1 isp e g mci39 l.jpg
Tier-1 ISP: e.g., MCI onto link or R bps

MCI US-Intercontinental backbone network

1: Introduction


Internet structure network of networks40 l.jpg

“Tier-2” ISPs: smaller (often regional) ISPs onto link or R bps

Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs

NAP

Tier-2 ISPs also peer privately with each other, or interconnect at NAP

  • Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet

  • tier-2 ISP is customer of

    tier-1 provider

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Internet structure: network of networks

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

1: Introduction


Internet structure network of networks41 l.jpg

“Tier-3” ISPs and local ISPs onto link or R bps

last hop (“access”) network (closest to end systems)

Tier 3

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

NAP

Local and tier- 3 ISPs are customers of

higher tier ISPs

connecting them to rest of Internet

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Internet structure: network of networks

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

1: Introduction


Internet structure network of networks42 l.jpg

a packet passes through many networks! onto link or R bps

Tier 3

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

local

ISP

NAP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP

Internet structure: network of networks

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

1: Introduction


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