CS 313 Introduction to Computer Networking & Telecommunication
description
Transcript of 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)
2
Topics Introduction Internetwork Layer Transport Layer Application Layer How is a Message Delivered
TAKE CS 413 IN FALL 2011
3
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
7
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
8
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!
10
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
15
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.
19
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)
20
UDP header
21
The TCP Segment Header
22
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 …
23
(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
24
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
25
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?)
26
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