Lecture 8Networks (contd.)

Media (wired and wireless);

Topology (bus, star, mesh, ring, tree);

Protocol (HTTP, TCP/IP, MAC);

Addressing (IP, MAC);

Naming (domain, hostnames);

Layered Communication (TCP/IP model);

Networking devices (hubs, switches, routers);

Routing and Internetworking;

Recap of Network lectures

1. (Inter)networking application: how email works?

2. Network classification: According to scope (campus, metropolitan, home); According to paradigm (server-based, peer-to-peer) ; According to hierarchy (core, access); According to type (intranet, internet, extranet, VPN).

3. Network technologies: Core network: MPLS (packet switching), ATM (cell switching) Access network: narrowband (dial-up), broadband (DSL,

Cable, WiMax)

Today’s lecture outline

How email works?

1

User sends email

SMTP data

Source MAC address | Destination MAC address 23:34:aa:bb:cc:dd | 12:34:aa:bb:cc:dd

FCSPayload

Payload

Source Port | Destination Port> 1024 | 25

Payload

Payload

Source IP | Destination IP 202.125.157.150 | 115.186.131.69

Payload

Application layer

Transport layer

Link layer

Internet layer

This is a mail client software (e.g., Outlook Express (shown); Mozilla Thunderbird)

Compare with browser software:(Internet explorer; Mozilla Firefox)

Webmail.niit.edu.pk

Webmail.niit.edu.pk

User receives email

POP request

Source MAC address | Destination MAC address 23:34:aa:bb:cc:dd | 12:34:aa:bb:cc:dd

FCSPayload

Payload

Source Port | Destination Port> 1024 | 110 (POP)

Payload

Payload

Source IP | Destination IP 202.125.157.150 | 115.186.131.69

Payload

Application layer

Transport layer

Link layer

Internet layer

or IMAP requestor HTTP request

Source Port | Destination Port> 1024 | 143 ( if IMAP) Source Port | Destination Port> 1024 | 80 ( if HTTP)

or IMAP requestor HTTP request

Classification of Networks

Scope

HierarchyParadigm

2

Type

(Geographical Scope)Classification

• Wide Area Networks

• Metropolitan Area Networks

• Campus Area Networks

• Home Area Networks

• Personal Area Networks

Decreasing Scope

(Network Paradigm)Classification

Client-server networks:

Examples: DNS, HTTP, DBMS servers and client

(Network Paradigm)Classification

Peer-to-peer (P2P) networks:

Examples: Workgroup computing; P2P networks such as BitTorrent, Gnutella, Morpheus, etc.

(Hierarchy)Classification

Core

Distribution

Access

(Type)Classification

VPN

Image source: http://www.flexsys-group.com

Intranet

Extranet

Internet

Network technologies

Access network technologies

3

Core network technologies

Multi-protocol label switching (MPLS)• Packet based• Unified data-carrying service for both

circuit-based and packet-based clients

Asynchronous Transfer Mode (ATM)• Cell (small fixed sized packets) based

•Both ATM and MPLS allow traffic engineering

Core network technologies

• Uses analog telephone lines

• Utilizes a modulator/ demodulator (Modem)

• Modems perform error correction/ compression

• V.34 (28.8, 33.6 kbps); V.90 and V.92 (56 kbps)

• Telephone networks limit a single narrowband channel to 56 kbps

(Narrowband)Access technology

• Leased Circuits: E1 (2M), E2 (8M), E3 (34M)

• DSL: Utilizes telephone lines but performs efficient digital codingTypes: ADSL, HDSL, SDSL, VDSL

• Cable: Utilizes co-axial cables and provides similar access speeds to DSL

• WiMax: Wireless broadband technology

(Broadband)Access technology

Lecture’s

Summary

a) We described

how email works.

b) We classified networks

according to their

scope, paradigm

, hierarchy, and

type.

c) We discussed

narrowband

and broadband

data communications

.

???Questions/

Confusions?

Credits/ Acknowledgement can be found

at the course website:

http://tinyurl.com/5hb8pp