Computer Networks Class Notes - Class #1 CSC 8560 - Computer Networks and Open Systems Villanova University Computer Science Department Fall 2001

Computer Networks Class Notes - Class #1

CSC 8560 - Computer Networks and Open Systems

Villanova University

Computer Science Department

Fall 2001

2Villanova University Computer Networks

Agenda

Introductions Objectives? Review Syllabus (courtesy of Dr. Cassel) Administrative Stuff Overview of Computer Networks (see syllabus) HTML (see syllabus) Simple Web Forms (see syllabus)

All students are expected to prepare for class, show up and participate.


General Stuff

Syllabus available online at, – http://www.csc.vill.edu/~tconnoll/csc8560/syllabus.html

Office Hours: Thursday’s from 4:00 - 6:00, room ? E-Mail: [email protected] unix accounts have been setup on the CSC cluster and

Doyle (G50) – See me after class for userid/passwd if not known

Network logins setup on PC’s in G50 Teaching Assistant - Hongyi Li


General Stuff

Grading– No tests!

– Class attendance/participation

– Assignments

– Extra effort

Text: – Computer Networks and Open Systems - An

Application Development Perspective, Cassel and Austing

Feedback/questions?


Additional Information

Computer Networks, Third Edition – Andrew S. Tannenbaum, Prentice Hall, 1996.

Internet Request For Comments (RFC) – http://www.faqs.org/rfcs


Overview of Computer Networks Peer-to-peer networking only Networking Benefits?

– Shared resources, reliability, incremental growth, performance

Network issues affect every aspect of computing Data Communications

– Control/sharing of communications channel, message encoding, error handling, re-transmission, packetizing, packet ordering, etc.

– Network Applications typically unaware of these lower-level issues/activities - TRANSPARENCY


Overview of Computer Networks Network requires 3 components:

– Transmission medium; network interface; network software

– Network software is similar to operating system software - assists user in gaining access to system resources and protects the system

Networks provide interoperability between processes – Cooperative operation depends on common

understanding - agree on format/meaning of messages and conditions - called a PROTOCOL


Overview of Computer Networks

Protocol Example (ConfirmAndDisplay) Protocol Conflicts Resolving conflicts (standards)

– Select one of the competing protocols (de facto)

– Drop existing protocols and develop a new one

– Support multiple protocols

– Keep original and support new global protocol



Layered Architecture– Services built from simpler services– Layer N makes services available to layer N+1

• Services: a set of primitives that a layer provides to the layer above

– Layering Principles: Each layer should, • Represent a different level of abstraction • Perform a well-defined function • Be chosen to minimize information flow across interfaces• Be reasonably sized - enough layers to allow for separating

functions that do not below together but not too many layers that the architecture becomes unwieldy



– Layers communicate Protocol Data Units (PDUs) between their peers - each layer encapsulates the previous layer’s PDU within the data section of its own PDU



Layering and the OSI model 7. Application

6. Presentation

5. Session

4. Transport

3. Network

2. Data Link

1. Physical

User-oriented services - layers 5 thru 7

Appl. PDU

Presentation PDU

Session PDU

Transport PDU

Network PDU

Data Link PDU

Data


(insert slides with descriptions of each layer)



Protocol Suites– ARPA protocols - also called DoD, DDN or TCP/IP

protocol suite.

– SNA (hierarchical, generally not scalable)

– APPN (IBM’s peer-to-peer protocol suite)

– ISODE (ISO compliant, also supports ARPA)

Network Classifications – Local Area Networks (LAN) - “802” protocols

– Wide Are Networks (WAN) -

– Metropolitan Area Networks (MAN)


Overview of Computer Networks Topology (transparent to user) - LAN’s only

– Daisy-chain – Bus – Ring – Star (or hub and spokes) – Tree

Internetworking – Repeaters - Physical layer – Bridges - Data Link layer – Routers - Network Layer – Gateways - Any layer


HTML Documents

See syllabus


Simple Web Forms

See syllabus


Coming Up Next

Read chapters 1 & 2 Web Search exercise - due 9/6 Begin web design - due 9/20 Web Applications (2 of them) - due 11/8 and 12/6

Questions/Comments???


Class Feedback

On a scale of 1 to 5, how helpful were the following:

___ Course material

___ Course exercises

___ Instructor’s presentation of material

___ Facilities

General Feedback: __________________________________________________

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________