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Introduction to Management Information
Systems
Chapter 5 Data Communications
and Internet Technology
HTM 304
Fall 07
4
Layer 3: Internet Layer
Runs the IP protocol
Data received from the above layers are divided into packets.
Key design issue – to determine how packets are routed from source to destination.
Routing: selecting paths – shorter route, avoiding heavy traffic, etc.
Router: special-purpose computing devices that process IP protocol – examine the destination IP addresses and decide where to send them.
5
IP Address (IPv4)
Layer 3 handles IP address.
The Logical Addresses
Assigned when you get online, not permanently tied with the MAC address
Why? Don’t have to update every time a NIC is changed
An IP address is four bytes, totally 32 bits.
How many in total?
You can either specify your IP address (as most of the company’s server), or let the ISP assign one dynamically.
6
IPv6
Windows Vista has adopted IPv6.
Totally 128 bits (=16 bytes) instead of 32 bits (=4 bytes)
How many total IPv6 addresses? 2128 3.4 * 1038 addresses
Approximately 5 * 1028 addresses * 6.5 billion people alive today.
Example of address: (8 Hexadecimal digits)
2001:0db8:85a3:08d3:1319:8a2e:0370:7334
7
Exercise: Find your IP address
How to find your IP address?
“start” “run”: type “cmd” and click ok, the command prompt
window will pop up
Type command “ipconfig” to observe the report
Use “ping” command to check the connectivity between two
computers
8
Router – 3rd Layer Equipment
Application Layer
Transport Layer
Internet Layer
Data Link Layer
Physical Layer
Computer A
Application Layer
Transport Layer
Internet Layer
Data Link Layer
Physical Layer
Internet Layer
Data Link Layer
Physical Layer
Computer B
Router A (can actually many)
Packets:Original IP – source IP + Data
Frames:Original MAC – Next MAC + Packets
Data Link Data Link
9
Explain: Why Router? – handle address
Can be substituted by a computer with routingPrograms installed. Multiple NICs needed.
10
Layer 4 Transport Layer
Handles transport protocol: TCP or UDP – software protocols
Application Layer
Transport Layer
Internet Layer
Data Link Layer
Physical Layer
Computer A
Application Layer
Transport Layer
Internet Layer
Data Link Layer
Physical Layer
Internet Layer
Data Link Layer
Physical Layer
Computer BRouter A (can actually many)
Data Link Data Link
Once paths from computer A to B is found, an end-to-end connection is established on the 4th layer. Meaning data can be transferred.
Point-to-point
11
Layer 4 Protocols
TCP: Transmission Control Protocol
Receive data and transmission request from Layer 5 (application layer)
Send communication request to layer 3, layer 3 will then find one or more
route to the destination computer.
Destination computer send acknowledge back, indicating there is end-to-
end connection.
Break data from layer 5 into segments, and send each segments with
confirmation. (destination computer send acknowledge upon receiving
every segment)
UDP: User Datagram Protocol
Designed for short messages
Does almost everything the same as the TCP, except not requesting
confirmation.
Faster, more efficient for short messages and time-sensitive application
12
Layer 5 The Application Layer
Layer 5 protocols for applications such as browsers, email, file
transfer, etc.
A standard email protocol
Simple Mail Transfer (SMTP)
Web page processing
Hypertext Transfer Protocol (HTTP)
File Transfer Protocol (FTP)
It governs how applications work with each other. (e.g. Firefox
v.s. IE 7)
15
Exercise
W
hich of the following is referred to as the
network cable?
Coaxial Cable
Fiber Optic Cable
Unshielded Twisted Pair
Twisted Pair Copper
16
More exercise?
What is the name of data unit
transferred on the 2nd layer?
Packet
Bytes
Package
Frame
Segment
17
Explain IEEE 802?
Which of the following standard in IEEE 802 is referred to
as Ethernet?
IEEE 802.11
IEEE 802.15
IEEE 802.3
IEEE 802.5
18
Describe the three topologies mainly used to connect a LAN. Describe the pros and cons.
Which one can be extended to a large geographic area
Which topology corresponds to the Ethernet?
Describe the difference between an “end-to-end” connection and a “point-to-point” connection?