cmpe 150 – winter 09 lecture 2 january 8, 2009 p.e. mantey
Post on 22-Dec-2015
215 views
TRANSCRIPT
CMPE 150 -- Introduction to Computer Networks
Instructor: Patrick Mantey [email protected] http://www.soe.ucsc.edu/~mantey/
Office: Engr. 2 Room 595J Office hours: Tuesday 3-5 PM TA: Anselm Kia [email protected] Web site: http://www.soe.ucsc.edu/classes/cmpe150/Winter09/
Text: Tannenbaum: Computer Networks (4th edition – available in bookstore, etc. )
Assignment #1
Available on the web site:http://www.soe.ucsc.edu/classes/cmpe150/Winter09/
Due Thursday January 15, 2009
Today’s Agenda
“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
Classification of Networks by Transmission Technologies
Broadcast Selection by addressing Multicast
Point-to-Point unicast
Home Network Categories
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).
Metropolitan Area Networks
A metropolitan area network based on cable TV -- New alternative is “WiMax” – IEEE 802.16
Wide Area Networks (2)
A stream of packets from sender to receiver-routers “store and forward” – “packet switching”
Wireless Networks Categories of wireless networks: System interconnection
Master/slave Wireless LANs (e.g. 802.11) Wireless WANs (e.g. 802.16)
Protocols 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 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 Syntax
Data formats Signal levels
Semantics Control information Error handling
Timing Speed matching Sequencing
Protocol Architecture
Task of communication broken up into modules
For example file transfer could use three modules File transfer application Communication service module Network access module
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.
Network Access Layer
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.)
Addressing Requirements
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 The service access point or SAP
Protocol Data Units (PDU)
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
TCP/IP Protocol Architecture
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 Application layer Transport layer (Host-to-host layer) Internet layer Host-to-Network layer
Network access layer Physical layer
Physical Layer 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)
Exchange of data between end system and network
Destination address provision Invoking services like priority
Internet (Network) Layer (IP)
Systems may be attached to different networks
Routing functions across multiple networks
Implemented in end systems and routers
OSI Model
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
Internet Layering
Level 5 -- Application Layer (rlogin, ftp, SMTP, POP3, IMAP, HTTP..)
Level 4 -- Transport Layer(a.k.a Host-to-Host)(TCP, UDP, ARP, ICMP, etc.)
Level 3 -- Network Layer (a.k.a. Internet) (IP)Level 2 -- (Data) Link Layer / MAC sub-layer
(a.k.a. Network Interface or Network Access Layer)
Level 1 -- Physical Layer