3 networking evolution

8/12/2019 3 Networking Evolution

1/20

Data Communication Network Evolution

Motivation

SNA

DNA

TYMNET

ARPANET


2/20

Layered communications protocol used by IBM forcommunications between IBM mainframes and devices

Uses token ring as the access method (IEEE 802.5)


3/20

Physical Units on an SNA Network


4/20


5/20

Provide reliable and tested communications withIBM systems

Disadvanta e requires special devices and complex training to

configure, manage and troubleshoot

Still used in some networks of Banks in USA


6/20

DNA

Di italNetwork

Architecture

Developed for use on networks using DEC computers

Architecture used by Digital Equipment Corporation computers (nowCompaq)

DNA Structured Model

Has eight layers

Man hardware latforms need to communicate

Protocols

Digital Data Communication Message Protocol (DDCMP)

X.25

erne


7/20


8/20


9/20

TYMNET

TYMNET was a commercial network

eve ope y are n .

TYMNET I, was designed to interface low-speed (10-30 character/s)

-

The data rate was low, the size of the network was small (less than100 nodes),

The log-on rate low (less than 10 new users/min).

nteracte w t u up ex term na s on a c aracter y c aracter

basis.


10/20

Mechanisms for data transmission in TYMNET

TYMNET was acket switched network

A tree structure for supervisory control of the original network

A virtual circuit approach for user data transmission andmu p ex ng over s ng e p ys ca n .

v rtua

c rcu t

sc eme

supports

no es

w t

sma u ers

memory.


11/20

-

Terminal-oriented

Interactive, Duplex system


12/20

ou ng n

routin is centralized virtual circuits

Uses adaptive shortest path routing algorithm (Dijkstras &

Bellman Fords)

The supervisory node computes the shortest path and sends a

needle packet to source that contains the routing information.


13/20

routin is centralized virtual circuits

Uses adaptive shortest path routing algorithm (Dijkstras &

Bellman Fords)

The supervisory node computes the shortest path and sends a

needle packet to source that contains the routing information.


14/20

vers ons

TYMNET-I :the supervisory node explicitly sets the routing tables at the nodes.

twas mp emente n 1 tm n computers.

TYMNET-II : routing tables are set by a set-up packets that precedes the

transmission of data.

.

Supports high density network

o e: ot vers ons use rtua rcu t pproac


15/20

erence w -

In TYMNET-I the supervisor maintains an image of theinternal routing tables of all the nodes and explicitly reads

and writes the tables in the nodes,

-

there is much less interaction between node and

supervisor.


16/20

in 1957Seen as a defeat by the US

Spurred on by President Kennedy and his

vision to ut man on the moon b the end

of the decade, two new agencies were formed

NASA and ARPA in the DoD (Department

SPUTNIK

ARPA was the founding agency of ARPANET

which eventually led to the Internet


17/20

ARPANET EVENTS

Build a minicomputer in each site as an interface betweennetwork & mainframe nodes

Processors

-corporation

By 1973, E-mail was 75% of all ARPANET Traffic

Also in 1973, TCP/IP was conceived by Vinton Cerf of Standford & BobKahn of DARPA

-is safely received at the following node (a store and forward system)


18/20

Layout of the ARPANET Hosts and terminals

"talk" with each other via the IMP-subnet.


19/20

ARPANET

message switched network.

received at the following node (a store and forwards stem

identical processors - kept at each node connect these processors to leased common-carrier

circuits to form a subnet

Research computers at each node are connected to these,

Processors (IMPs).


20/20

Growth of the ARPANET (a)December 1969, (b)July 1970,

, . .

The Evolution of ARPANET

3 networking evolution

Documents