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EE228a - Fall 2001 Communication Networks
Prof. Jean WalrandDepartment of EECS
University of CaliforniaBerkeley
Course Objectives & Contents
Explain Internet and related networksModels and Evaluation Technology
Links: ADSL, Cable Modem, Optical LANs: Ethernet Routers, Switches
Protocols Routing, Transport, Applications
Organization
One lecture every week: W 2:30 – 4:30
Grading: Quizzes: 30%, 2 Midterms: 30%, Project Report: 20%, Project Presentation: 20%
Instructor: Prof. Jean Walrand; OH: M 11:00 – 12:00
Web site: See Prof. Walrand’s home page
Contents
8/29: How Internet Works9/05: Ethernet, ATM, ADSL, Cable Modems9/12: Models, Analysis, Simulation9/19: Routing: OSPF, BGP, Ad Hoc, …9/26: Transmission Control10/03: Switching – Midterm 110/10: Optical Networks10/17: Wireless Networks10/24: Networks and Services Management –
Midterm 210/31: TM, NP, SAN, etc.11/07,11/14, 11/28: Student Presentations
Click -> get page page from local
or remote computer link:
http://cnn.com
specifies - protocol (http) - location (cnn.com)
Web: Example
Web: Example
Click -> get page page from local
or remote computer link:
http://cnn.com
specifies - protocol (http) - location (cnn.com)
Web: Example
Click -> get page page from local
or remote computer link:
http://cnn.com
specifies - protocol (http) - location (cnn.com)
Web: Locating Resource
cnn.com is the name of a computer (and, implicitly, of a file in that computer)
To find the address, the application uses a hierarchical directory service called theDomain Name System
loca l
com
host
cnn.com ?
cnn.com ?IP = a .b .c.d
IP = a .b .c.d
Web: Connection
The protocol (http) sets up a connection between the host and cnn.com to transfer the page
The connection transfers the page as a byte stream, without errors: pacing + error control
H ost cnn.com
Web: End-to-end
The byte stream flows from end to end across many links and switches: routing (+ addressing)
That stream is regulated and controlled by both ends: retransmission of erroneous or missing bytes; pacing
H O ST
C N N .C O M
end-to -end pacing anderro r con tro l
rou ting
Web: Packets
The network transports bytes grouped into packets
The packets are “self-contained” and routers handle them one by one
The end hosts worry about errors and pacing:Destination sends ACKsSource checks losses
C
H O S T: B
C N N .C O M : AA | B | # , C R C | bytes
B : toC
Web: Bits
Equipment in each node sends the packets as a string of bits
That equipment is not aware of the meaning of the bits
01011...011...110
Transm itte r P hysica l M edium R ece iver
01011...011...110
O ptica lC opperW ire less
Web: Points to remember
Separation of tasks send bits on a link: transmitter/receiver [clock, modulation,
…]
send packet on each hop [framing, error detection,…]
send packet end to end [addressing, routing]
pace transmissions [detect congestion]
retransmit erroneous or missing packets [acks, timeout]
find destination address from name [DNS]
Scalability routers don’t know about connections names and addresses are hierarchical