Transcript CS412 Computer Networks - Winona State University

CS 313 Introduction to
Computer Networking &
Telecommunication
(Teach Yourself)
The TCP/IP Internet
(in 60 minutes)
Chi-Cheng Lin, Winona State University
Topics
Introduction
 Internetwork Layer
 Transport Layer
 Application Layer
 How is a Message Delivered
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
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-switching
Point-to-point
Expanded to become the backbone of the
Internet
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Introduction
The Internet is an interconnected collection of
many networks.
Internet Network Layer Design Principles
1. Make
sure it works
2. Keep it simple
3. Make clear choices
4. Exploit modularity
5. Expect heterogeneity
...
Internet Network Layer Design Principles
...
6. Avoid static options and parameters
7. Look for good design (not perfect)
8. Strict sending, tolerant receiving
9. Think about scalability
10.Consider performance and cost
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

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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
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Note that a router has more
than one IP addresses!
Two switched Ethernet LANs joined by a router
IP
Transmission mechanism used by the
TCP/IP
 Unreliable, connectionless datagram
protocol
 Best-effort service
 Reliability?

Provided by upper layers (e.g., TCP or …)
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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
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/Network
A
27
224
B
214
216
C
221
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Actual numbers might be less, because of …
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IP Addresses
Special IP addresses
IP Addresses

Dotted decimal format
32 bits are grouped into 4 bytes
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Each byte is represented in decimal
Two adjacent bytes are concatenated
using a dot
Example:
10001010 00011000 00101000 00000001
Dotted decimal format:
Which class is it in?
Network address:
Host address:
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Internet Control Protocols
The principal ICMP message types.
Transport Layer

Two protocols
UDP (User Datagram Protocol)
Connectionless
TCP (Transmission Control Protocol)
Reliable, connection-oriented stream protocol

IP
Host-to-host

TCP or UDP
Port-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 198.174.76.151
IP address of the router on the network that
the host is on is 198.174.76.254
IP address of the web site is 199.17.166.97
IP 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
Protocol Stack
Network Configuration
198.174.76.151
198.174.76.254
HTTP
TCP
IP
IEEE 802.3
CSMA/CD Ethernet
Internet
199.17.166.97
199.17.166.1
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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
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