Intro Computer Networks Part 1: Introduction

4 pieces of information your machine needs

1. IP Address v4

2. Subnet Mask

3. IP Address of Local DNS

4. IP Address of Local Router

5. (optional) GBT

Hosts

end systems

Communication links

Fiber, copper, radio, satellite

Bandwidth

transmission rate

Packet switches

forward packets (chunks of data). Examples include: routers and switches

3 components of the internet

Hosts, communication links, packet switches

Internet

network of networks. Loosely hierarchical

Protocols

control sending and receiving of messages (ex: TCP, IP, HTTP, FTP, PPP)

RFC

Request for Coments

IETF

Internet Engineering Task Force

Protocols define 4 things:

1. types of messages

2. syntax of messages

3. semantics of the messages

4. rules associated with the messages

Network Edge

applications and hosts

Client/Server Model

Client host requests, receives service from server (ex: WWW client aka browser/server, email client/server

Peer to peer model

Host interaction is symmetric (ex: Napster, Gnutella, KaZaA, BitCoin)

UDP

User Datagram Protocol: Internet’s connectionless service (unreliable data transfer, no flow control, no congestion control)

TCP

Transmission Control Protocol: connection-oriented (like the telephone)

Apps using TCP

HTTP (www), FTP (file transfer), Telnet (remote login), SMTP (email)

Apps Using UDP

Streaming media, teleconferencing, Internet telephony

How to connect to end systems to edge router?

1. Residential access nets (cable modem)

2. Institutional access networks (school, company) - local area networks

3. Mobile access networks

Physical media

Coax, fiber, and radio (wifi)

Circuit switching

dedicated circuit per call - telephone network. End-end resources reserved for “call”. Dedicated resources: no sharing. Dedicated path is established between sender and receiver.

Network resources divided into “pieces”, idle if not used, based on frequency division or time division.

Packet switching

data sent through network in discrete “chunks”. End-end resources divided into packets. Resource contention, allows more users to use network. Message is broekn into individual chunks called packets.

Datagram network

Destination address determines next hop.

Connectionless switching, path is not fixed, datagrams contain destination information and intermediary devices use this information to forward datagrams to right destination.

Virtual circuit network

Each pack carries tag (virtual circuit ID), tag determines next hop

connection-oriented switching. a prepared route is established before messages are sent.

National/international backbone providers (NBPs)

BBN/GTE, AT&T, IBM, UUNet. Interconnection (peer) with each other privately, or at public NAPs (network access point)

Regional ISPs

connect into NBPs

Local ISP

company, connect into regional ISPs

POP

point of presence

Internet Protocol Stack

Application, Transport, Network, Link, Physical

Application

supporting network applications. FTP, SMTP, HTTP

Message

Transport

host to host data transfer. TCP, UDP

Segment

Network

routing of datagrams from source to destination. IP, routing protocols

Datagram

Link

data transfer between neighboring network elements. PPP, ethernet

Frame

Physical

bits “on the wire”, “over the air”