CS 313 Introduction to Computer Networking & Telecommunication

Chi-Cheng Lin, Winona State University

CS 313 Introduction to Computer Networking &

Telecommunication(Teach Yourself)

The TCP/IP Internet(in 60 minutes)

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Topics Introduction Internetwork Layer Transport Layer Application Layer How is a Message Delivered

TAKE CS 413 IN FALL 2011

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Introduction The Internet

Internetworking using the TCP/IP protocol suite

internet = internetworking ARPANET, 1960

Packet-switchingPoint-to-pointExpanded to become the backbone of

the Internet

Introduction

The Internet is an interconnected collection of many networks.

Internet Network Layer Design Principles

1.Make sure it works2.Keep it simple3.Make clear choices4.Exploit modularity5.Expect heterogeneity

. . .

Internet Network Layer Design Principles

. . .6.Avoid static options and parameters7.Look for good design (not perfect)8.Strict sending, tolerant receiving9.Think about scalability10.Consider performance and cost

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Internetwork Layer Protocols ARP (Address Resolution Protocol) IP (Internet Protocol) ICMP (Internet Control Message

Protocol)For a router to report datagram problem

back to source IGMP (Internet Group Management

Protocol)Multicasting

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ARP Physical address is needed to deliver a message to the

destination ARP: Given an IP address of a computer, find its physical

address Q: How does source ask destination without knowing

destination address? A: Broadcasting ARP request Q: How does destination answer? Broadcasting back? A:

_______ ARP only works on the same network

Q: How can a message be delivered to a destination on another network

A: Router answers ARP request! Q: How can ARP’s performance be improved (i.e., to

reduce the broadcasting traffic)? A: one of our favorite mechanisms in CS _________

Q: What if a host reconfigured? A: Gratuitous ARP

Two switched Ethernet LANs joined by a router

Note that a router has more than one IP addresses!

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IP Transmission mechanism used by

the TCP/IP Unreliable, connectionless

datagram protocol Best-effort service Reliability?

Provided by upper layers (e.g., TCP or …)

The IP Version 4 Protocol

The IPv4 (Internet Protocol) header.

The IP Version 4 Protocol

Some of the IP options.

IP Addresses

An IP prefix.

Classful IP Addresses

IP address formats

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IP Addresses IP address is hierarchical, not flat

Two parts: network and host Theoretically

How many networks of a particular class is possible?

How many hosts are in a network of a particular class?

Class #Networks #Hosts/NetworkA 27 224 B 214 216 C 221 28

Actual numbers might be less, because of …

IP Addresses

Special IP addresses

IP Addresses Dotted decimal format

32 bits are grouped into 4 bytes Each byte is represented in decimal Two adjacent bytes are concatenated

using a dot Example:

10001010 00011000 00101000 00000001Dotted decimal format:Which class is it in?Network address:Host address: 17

Internet Control Protocols

The principal ICMP message types.

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Transport Layer Two protocols

UDP (User Datagram Protocol)Connectionless

TCP (Transmission Control Protocol)Reliable, connection-oriented stream protocol

IPHost-to-host

TCP or UDPPort-to-port (application-to-application,

process-to-process)

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UDP header

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The TCP Segment Header

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Application Layer Protocols Domain Name System (DNS)

Translate name to IP address Electronic mail

Simple Mail Transfer Protocol (SMTP)Internet Message Access Protocol (IMAP)Multipurpose Internet Mail Extensions (MIME)

File Transfer Protocol (FTP) Hypertext Transfer Protocol (HTTP) Dynamic Host Configuration Protocol

(DHCP)

And many more …

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(Not Too) Big Picture* Scenario: Request to download a

document from www.winona.edu IP address of the host 198.174.76.151IP address of the router on the network

that the host is on is 198.174.76.254IP address of the web site is

199.17.166.97IP address of the router on the network

that the web site is on is 199.17.166.1*Internet: The Big Picture (by Russ Haynal): http://navigators.com/internet_architecture.html

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Big Picture

HTTP

TCP

IP

IEEE 802.3CSMA/CD Ethernet

Protocol Stack Network Configuration

199.17.166.97

198.174.76.151 198.174.76.254

199.17.166.1

Internet

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Big Picture Steps

Name IP address by DNS (Domain Name System, an application layer protocol and a distributed database)

Port required to specify application: server: 80 for http (199.17.166.97:80)client: obtain a port number

Destination network address used for routing (hierarchical routing)

A connection has to be set up first (TCP or UDP?)

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Big Picture Steps (cont’d)

ARP is used for 198.174.76.151 to find the “physical address” of 199.17.166.97. (What will be returned?)

Data: 198.174.76.151 198.174.76.254 intermediate routers 199.17.166.1

When data received by 199.17.166.1, ARP is used to find the physical address of destination host 199.17.166.97

Data: 199.17.166.1 199.17.166.97