CS-09 – Data Communications and Networks

 

 

AGENDA

 

 

Why we talk of Computer Networks

 

Mainframes vs. Computer Networks

 

Distributed Computing vs. Computer Networks

 

Computer Networks Usage

 

Distributed Computing vs. Networks

 

Network Technical Issues

 

LAN-MAN-WAN

 

Internetworks

                                     

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Why do we talk of Computer Networks

·        Centuries on Move

 

·                  18th Century – Mecanical Systems (Industrial Revolution)

·                  19th Century – Steam Engine (Surface Transport)

·                  20th Century – Information Age (Transport w/o Movement)

·                  21st Century – Biotech Age (Transport all Human Senses)

 

·        Key Focus in past few centuries is transporting & thus it requires

 

NETWORKS

(An interconnection between entities that works to transfer something)

 

·        Primary Work = Information Transfer

·        Primary Information Management Tool = Computers

 

Thus we talk of

 

COMPUTER NETWORKS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mainframes Giving Way to Computer Networks

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


q       Computer Network Definintion excludes computer setups where one computing node is forcibly started by some main computer.

Distinction Between Distributed Computing and Computer Networks

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Computer Networks Usage

 

Usage by companies

·                 Resource Sharing

·                 Reliability (by having alternative source of information, Mirrors)

·                 Cost Saving (Common File Server, Application Server)

·                 Client Server Implementation.

·                 Scalability (Increase Load as workload increases)

·                 Employee communication medium

 

Usage by people

·                 Access to remote information (News, Library, Magazines, Bank Transaction, Equipment Information, Service procedures, Tour planning, Health information).

·                 Person to Person Communication ( Email, Chat, Pager, Newsgroup, Audio-Conferencing, Video-Conferencing etc.)

·                 Interactive Entertainment (Music Tracks, Movies on demand, Online Games etc.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Computer Networks Technical Issues

 

Issues relate to two aspects

·                  Transmission Technology Aspect

·                  Scale aspect (Physical Spread of Network)

 

Transmission Technology

·                  Broad-Cast Networks

(Packets received by all but used by whom it is meant for. Broadcasting is supported to all, group (Multi-casting), Individuals).

·                  Point to Point Network

(Packets passes thru individual intermediate machines and reaches specified destination via a resolved route.)

 

Network Spread

·                  0.1 m                                 Data-Flow Machine/Circuit Board

·                  1 m                                     Computer System

·                  1 m – 1km                        LAN

·                  1 Km – 10 km                  MAN

·                  10 Km – 1000 Km           WAN

·                  1000 Km +                        Internetwork           

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LAN – Local Area Network

 

·        Privately owned – upto few km in size

·        Connects PCs, Workstations, Peripherals in a room, building or campus.

 

Size

·                  Worst-case transmission time is known in advance

·                  Permits usage of simpler technologies

 

Transmission Technology

 

·                  Single cable connecting many computers

·                  10/100 Mbps traditional speeds

 

Topology

·                  BUS (IEEE – 802.3 , Ethernet, 10/100 Mbps)

 

 

 

 

 

 


·                  RING (IEEE – 802.5, IBM Token Ring, 4/16 Mbps)

 

 

 

 

 

 

 

 

 


·        Arbitration and conflict resolution requirements

·        Static or dynamic channel allocation (Timeslot is prefixed or allotted dynamically)

·        Dynamic Allocation is centralised or de-centralised.

 

 

 

 

 

MAN – Metropolitan Area Network

 

·        Bigger version of LAN, owned privately by big corporates or city service providers.

·        Connects nodes of nearby corporate offices, multiple buildings etc.

·        IEEE classified it separately as 802.6 because of using a specific technology DQDB – Distributed Query Dual Bus

 

 

 

 

 

 

 

 

 

 

 

 

 

 


·        Design without switch

·        Bus arbitration simple and efficient

·        Less traffic collision

 

 

 

 

 

 

 

 

 

 

 

 

WAN – Wide Area Network

 

·        Spans a large area – country, continent, globe

·        Collection of Individual/distributed running application.

·        M/C running application are called Hosts (End System)

·        Generally refers to host networks with similar technologies.

·        Hosts connected by sub-nets.

 

SUB-NETS

·        Transmission Line (Circuits, Channels, Trunks)

·        Switching Elements (Packet switching nodes, intermediate systems, Data-switching-exchanges, ROUTERS )

 

 

 

 

 

 

 

 

 

 

 

·        Point-to-Point

·        Store and Forward

·        Packet Switching

 

·        Topologies

 

(Star, Ring, Tree, Complete, Intersecting Ring, Irregular)

 

 

 

Internetworks

 

·       Connects different and incompatible networks.

·       Connects thru Gateways.

·       internet ( Internet is a specific instance of internet)

·       Subnet – Collection of routers and transmission lines

·       WAN – Collection of routers, hosts and transmission lines

·       internetwork – WAN with mutiple types hosts and network technolgies.

·       Teminology not standardised

·       E.g. – America Online, ProdigyNet , compuserve, Internet etc.