CMPE 150 – Winter 09
Lecture 2
January 8, 2009
P.E. Mantey
CMPE 150 -- Introduction to
Computer Networks
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Instructor: Patrick Mantey
mantey@soe.ucsc.edu
http://www.soe.ucsc.edu/~mantey/
Office: Engr. 2 Room 595J
Office hours: Tuesday 3-5 PM
TA: Anselm Kia akia@soe.ucsc.edu
Web site: http://www.soe.ucsc.edu/classes/cmpe150/Winter09/
Text: Tannenbaum: Computer Networks
(4th edition – available in bookstore, etc. )
Syllabus
Assignment #1
Available on the web site:
http://www.soe.ucsc.edu/classes/cmpe150/Winter09/
Due Thursday January 15, 2009
Today’s Agenda
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“Big Picture”, terminology
Networking Overview (continued)
Protocol Concepts
Network Software
Architecture(s)
History (ARPA Net, NSF Net)
Networks Today: ATM, Ethernet, etc.
Network Hardware
Local Area Networks
 Metropolitan Area Networks
 Wide Area Networks
 Wireless Networks
 Home Networks
 Internetworks
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Classification of Networks by
Transmission Technologies
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Broadcast
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Selection by addressing
Multicast
Point-to-Point
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unicast
Classification of interconnected
processors by scale
Home Network Categories
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Computers (desktop PC, PDA, shared peripherals
Entertainment (TV, DVD, VCR, camera, stereo,
MP3)
Telecomm (telephone, cell phone, intercom, fax)
Appliances (furnace, air conditioner, oven, clothes
dryer, pool pump, lights, microwave, refigerator..)
Telemetry (utility meter, burglar alarm, babycam).
Local Area Networks
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Two broadcast networks
(a) Bus
(b) Ring (e.g. IEEE 802.5)
Metropolitan Area Networks
A metropolitan area network based on cable TV
-- New alternative is “WiMax” – IEEE 802.16
Wide Area Networks
Relation between hosts on LANs and the subnet.
Wide Area Networks (2)
A stream of packets from sender to receiver-routers
“store and forward” – “packet switching”
Wireless Networks
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Categories of wireless
networks:
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System interconnection
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Master/slave
Wireless LANs (e.g. 802.11)
 Wireless WANs (e.g. 802.16)
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Wireless Networks
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(a) Bluetooth configuration
(b) Wireless LAN
Protocols
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Used for communications between entities in a
system
Must speak the same language
Entities
 User applications
 e-mail facilities
 terminals
Systems
 Computer
 Terminal
 Remote sensor
Layered Architecture
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Each layer offers a service
Details of how service is offered in
hidden
Each layer talks to the layer
immediatley “above” and the layer
“below”
“protocol”: communication rules
Key Elements of a Protocol
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Syntax
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Semantics
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Data formats
Signal levels
Control information
Error handling
Timing
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Speed matching
Sequencing
Network Software
Protocol Hierarchies
Layers, protocols, and interfaces.
Protocol Architecture
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Task of communication broken up into
modules
For example file transfer could use
three modules
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File transfer application
Communication service module
Network access module
Connection-Oriented and
Connectionless Services
Six different types of service.
Service Primitives
Five service primitives for implementing a
simple connection-oriented service
(Tannenbaum, pg. 35-6)
Service Primitives (2)
Packets sent in a simple client-server
interaction on a connection-oriented network.
Services to Protocols
Relationship
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The relationship between a service and a protocol.
Simplified File Transfer
Architecture
Stallings Chapter 1
A Three Layer Model
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Application Layer
Transport Layer
Network Access Layer
Network Access Layer
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Exchange of data between the
computer and the network
Sending computer provides address of
destination
May invoke levels of service
Dependent on type of network used
(LAN, packet switched etc.)
Transport Layer
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Reliable data exchange
Independent of network being used
Independent of application
Application Layer
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Support for different user applications
e.g. e-mail, file transfer
Addressing Requirements
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Two levels of addressing required
Each computer needs unique network
address
Each application on a (multi-tasking)
computer needs a unique address
within the computer
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The service access point or SAP
Protocol Architectures and
Networks
Stallings Chapter 1
Protocols in Simplified
Architecture
Stallings Chapter 1
Protocol Data Units (PDU)
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At each layer, protocols are used to communicate
Control information is added to user data at each layer
Transport layer may fragment user data
Each fragment has a transport header added
 Destination SAP
 Sequence number
 Error detection code
This gives a transport protocol data unit
Network PDU
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Adds network header
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network address for destination computer
Facilities requests
Operation of a Protocol
Architecture
TCP/IP Protocol Architecture
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Developed by the US Defense Advanced
Research Project Agency (DARPA) for
its packet switched network (ARPANET)
Used by the global Internet
No official model but a working one.
TCP/IP Reference Model
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Application layer
Transport layer (Host-to-host layer)
Internet layer
Host-to-Network layer
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Network access layer
Physical layer
Physical Layer
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Physical interface between data
transmission device (e.g. computer) and
transmission medium or network
Characteristics of transmission medium
Signal levels
Multiplexing / demultiplexing
Data rates
etc.
Network Access Layer
(Host-to-Network Layer)
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Exchange of data between end system
and network
Destination address provision
Invoking services like priority
Internet (Network) Layer (IP)
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Systems may be attached to different
networks
Routing functions across multiple
networks
Implemented in end systems and
routers
Transport Layer (TCP)
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Reliable delivery of data
Ordering of delivery
Application Layer
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Support for user applications
e.g. http, SMPT
TCP/IP Protocol Architecture
Model
Stallings Chapter 1
OSI Model
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Open Systems Interconnection
Developed by the International
Organization for Standardization (ISO)
Seven layers
A theoretical system delivered too late!
TCP/IP is the de facto standard
OSI Layers
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Application
Presentation
Session
Transport
Network
Data Link
Physical
OSI vs TCP/IP
(From Stallings, Ch. 1)
Internet Layering
Level 4
-- Application Layer
(rlogin, ftp, SMTP, POP3, IMAP, HTTP..)
-- Transport Layer(a.k.a Host-to-Host)
Level 3
Level 2
(TCP, UDP, ARP, ICMP, etc.)
-- Network Layer (a.k.a. Internet) (IP)
-- (Data) Link Layer / MAC sub-layer
Level 1
(a.k.a. Network Interface or
Network Access Layer)
-- Physical Layer
Level 5