Professor Douglas Lyon Lyon@docjava.com Fairfield University http://www.docjava.com

Computer Networks CR320

Course Text

Java for Programmers Available from:

– http://www.docjava.com

Grading

Midterm: 1/3 Homework: 1/3 Final: 1/3 Midterm and Final – Take home!

Email

Please send me an e-mail asking to be placed on the CR320 List

E-mail: lyon@docjava.com

Pre-reqs

You should have CS232 and MA 172 OR permission of the instructor You need a working knowledge of

Java!

DATA COMMUNICATION NETWORKS

Communication networks

switched unswitched

Switched

Circuit Switched Packet Switched

DATA COMMUNICATION NETWORKS

Unswitched(broadcast nets)

DATA COMMUNICATION NETWORKS

packet radio satellite local

Packet switched nets are store and forward nets.

ckt switched nets have dedicated communication paths (i.e. telephone)

For example:

DATA COMMUNICATION NETWORKS

net station

node

A Broadcast Comm. Net can be WAN, the media is unshared

DATA COMMUNICATION NETWORKS

Dish

LAN EXAMPLES:

DATA COMMUNICATION NETWORKS

Ethernet with a bus topology:

DATA COMMUNICATION NETWORKS

Ring topology net:

Note: No switching nodes ,media is shared in LAN

For packet radio,every station can hear every other,the media is shared so this is a LAN technology

Computer Communications Architecture

The Three Layer ModelApplication run on computer which use

networks

network layer - xchange of data between computer

and network transport layer - error detection and correction application layer - file xfer etc.

Transmission Terminology

ANSI Defs:–simplex - one direction only–half-duplex - two-way but not at the same time.

– full-duplex - simultaneous two way transmission

Transmission Terminology

CCITT– CCITT vs ANSI– simplex = half-duplex– duplex = full-duplex

CCITT = international telegraph and telephone consultive committee

ISO-OSI ModelISO= International Standards Organization

OSI = Open Systems Interconnection

OSI Model = a 7 layer model used to describe most networks today

1. Physical Layer

This is a physical connection between machines. BITS

2. Data Link Layer

Provides reliable transfer of information across the physical links. FRAMES/Packets or DLPDU

3. Network Layer

Routing

4. Transport Layer

error recovery and flow control

5. Session Layer

Control for communication, close and open connections

6. Presentation LayerData formatting and character code conversion

7. Application Layer

file transfer, virtual terminals, electronic mail

etc..