Download OSI Model - DePaul University

OSI Model
CS363-Winter 1999
DePaul University
Group Project Info
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Teams formed and on the web
Cases
Working in Groups
Last half of class tonight reserved for
projects
Review #1
• You must connect a research institution’s
main offices with the testing site 30 miles
away. You will connect them with fiber
optic cable. Which type of fiber will you
use and why?
Review #2
• You are replacing your thicknet backbone
between your servers with a high-speed
network cable. You are considering using
Category 5 twisted-pair copper or
multimode fiber cable.
– Under what circumstances will you install the
fiber?
– Under what circumstances will you not use
fiber?
Review #3
• Your company recently renovated its
telephone system, including cabling, and
had extra cable installed for future growth.
Now you would like to use the excess
cabling to network the computers in your
company.
– What sort of network performance (data
capacity and cable length) can you reasonable
expect from these new telephone cables?
– What could you do with the old telephone cable
Review #4
• You would like to attach your notebook
computer to your LAN, but it does not have
a PCMCIA slot or a place for a proprietary
network card. How can you attach it to the
network?
OSI Model
• Why do we keep talking about this? Why
should we care?
Protocol Stacks
• =>group of protocols arranged on top of
each other as part of a communications
process.
• Importance of protocol stacks
Peer-Layer Communication
Between Stacks
Physical Layer
• Functions
• Components
Data-Link Layer
• Functions
• Components
Network Layer
• Functions
• Components: routers and gateways
Transport Layer
• Functions
• Components
Session Layer
• Functions
• Components
Presentation Layer
• Functions
• Components
Application Layer
• Functions
• Components
Problem
• Your company wants to use data link layer
encryption devices to send private data over
a public wide area network. What effect will
this have on devices in other layers?
Problem
• When trouble-shooting your network with a
packet sniffer, you find a device generating
spurious TCP/IP packets. Which devices are
suspect?
Drivers
• =>
• NDIS
• ODI
Network Protocols
• =>agreed-upon ways in which computers
exchange information
How Protocols Work
• Sending::
– Packetize data
– Appropriately address the packets
– Present packets to the network for delivery
• Receiving:
– -Accept packets from the network
– Remove transmitting information (addresses)
added in the sending process
– Reassemble data packets into original message
Network Packets
• Packet Structure
– Header=>
– Data=>
– Trailer=>
Packet Assembly
• Routing
• Protocol Stacks
Binding Protocols
Two Types of Protocols
• Connection-Oriented
• Connectionless
Standard Protocol Stacks
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ISO/OSI
SNA
DECnet
NetWare
AppleTalk
TCP/IP
Microsoft Supported Transport
Protocols
• NetBEUI
• NWLink
• TCP/IP
Other Protocols whose names
you should know
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SMTP
SNMP
NFS
X.25
X Windows
Problem:
• Your boss wants you to speed up the office
LAN without spending any money. You are
currently using 10Mbps Ethernet and
TCP/IP. Users connect to the Internet using
dial-up modems, and a single Ethernet
domain is in use. What do you do?
Problem:
• Your company network has become very slow, so
you decide to break it up into multiple domains
and use a router to connect the domains. As soon
as you disconnect the networks, even with the
router running properly, you can’t get data
between networks. You are using four Windows
NT servers (one in each subnetwork) running on
Ethernet with NetBEUI. You’ve spent your budget
on the router and can’t afford to purchase new
hardware. What is wrong? How can you fix it?