n etwork p rogramming csc- 341 instructor: junaid tariq, lecturer, department of computer science
TRANSCRIPT
NETWORK PROGRAMMING
CSC- 341
Instructor:
Junaid Tariq,
Lecturer,
Department of Computer Science
Lecture 33
NETWORK COMPONENTS
Physical MediaInterconnecting DevicesComputersNetworking SoftwareApplications
NETWORKING MEDIA Networking media can
be defined simply as the means by which signals (data) are sent from one computer to another (either by cable or wireless means).
Wide variety of transmission links:Copper Twisted pairCoaxial CableOptical FiberWireless media
Introduction to Computer Networks
NETWORKING DEVICES HUB, Switches, Routers,
Wireless Access Points, Modems etc.
Introduction to Compute Networks
COMPUTERS: CLIENTS AND SERVERS In a client/server network
arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients.
The server contains the file, print services, application, security, and other services in a central computer that is continuously available to respond to client requests.
Introduction to Computer Networks
APPLICATIONS E-mail Searchable Data (Web Sites) E-Commerce News Groups Internet Telephony (VoIP) Video Conferencing Chat Groups Instant Messengers Internet Radio
ADDRESSING AND ROUTING
Address: byte-string that identifies a node usually unique
Routing: forwarding decisions process of determining how to forward
messages to the destination node based on its address
Types of addresses unicast: node-specific broadcast: all nodes on the network multicast: some subset of nodes on the
network
WRAP-UP
A network can be constructed from nesting of networks
An address is required for each node that is reachable on the network
Address is used to route messages toward appropriate destination
LAYERED TASKSLAYERED TASKS
We use the concept of We use the concept of layerslayers in our daily life. As an in our daily life. As an example, let us consider two friends who communicate example, let us consider two friends who communicate through postal mail. The process of sending a letter to a through postal mail. The process of sending a letter to a friend would be complex if there were no services friend would be complex if there were no services available from the post office. available from the post office.
LAYERED TASKS
Sender, Receiver and Carrier
LAYERED TASKS
Hierarchy Higher Layer Middle Layer Lower Layer
Services The Each layer uses the services of the layer
immediately below it.
ORGANIZATION OF AIR TRAVEL
ticket (purchase)
baggage (check)
gates (load)
runway takeoff
airplane routing
ticket (complain)
baggage (claim)
gates (unload)
runway landing
airplane routing
airplane routing
Although this course is about network programming
(and not about networking in general), an understanding
of a complete network model is essential.
ORGANIZATION OF AIR TRAVEL: A DIFFERENT VIEW
Layers: each layer implements a service via its own internal-layer actions relying on services provided by layer below
ticket (purchase)
baggage (check)
gates (load)
runway takeoff
airplane routing
ticket (complain)
baggage (claim)
gates (unload)
runway landing
airplane routing
airplane routing
DISTRIBUTED IMPLEMENTATION OF LAYER FUNCTIONALITY
ticket (purchase)
baggage (check)
gates (load)
runway takeoff
airplane routing
ticket (complain)
baggage (claim)
gates (unload)
runway landing
airplane routing
airplane routing
Dep
art
ing
air
port
arr
ivin
g
air
port
intermediate air traffic sites
airplane routing airplane routing
THE OSI MODELTHE OSI MODEL
Established in 1947, the International Standards Established in 1947, the International Standards Organization (Organization (ISOISO) is a multinational body dedicated to ) is a multinational body dedicated to worldwide agreement on international standards. An ISO worldwide agreement on international standards. An ISO standard that covers all aspects of network standard that covers all aspects of network communications is the Open Systems Interconnection communications is the Open Systems Interconnection ((OSIOSI) model. It was first introduced in the late 1970s. ) model. It was first introduced in the late 1970s.
ISO is the organization.OSI is the model.
LAYERED ARCHITECTURE
The OSI model is composed of seven layers ; Physical (layer1), Data link (layer2), Network (layer3)
Transport (layer4), Session (layer5), Presentation (layer6), Application (layer7)
Layer Designer identified which networking functions had
related uses and collected those functions into discrete groups that became the layers.
The OSI model allows complete interoperability between layers.
The Each layer uses the services of the layer immediately below it.
Figure 2.2 Seven layers of the OSI model
Layered Architecture (cont’d)Layered Architecture (cont’d)
All
People
Seem
To
Need
Data
Processing
PEER-TO-PEER PROCESSES
Layer x on one machine communicates with layer x on another machine - called Peer-to-Peer Processes.
Interfaces between Layers Each interface defines what information and services a layer must provide for the layer above it. Well defined interfaces and layer functions provide modularity to a network
Organizations of the layers Network support layers : Layers 1, 2, 3 User support layer : Layer 5, 6, 7
It allows interoperability among unrelated software systems Transport layer (Layer 4) : links the two subgroups
OSI ARCHITECTURE
Figure 2.3 The interaction between layers in the OSI model
Peer-to-peer Processes (cont’d)Peer-to-peer Processes (cont’d)
Figure 2.4 An exchange using the OSI model
The data portion of a packet at level N-1 carries the whole packet
from level N. – The concept is called encapsulation.
Peer-to-peer Processes (cont’d)Peer-to-peer Processes (cont’d)
LAYERS IN THE OSI MODELLAYERS IN THE OSI MODEL
In this section we briefly describe the functions of each In this section we briefly describe the functions of each layer in the OSI model.layer in the OSI model.
Physical LayerData Link LayerNetwork LayerTransport LayerSession LayerPresentation LayerApplication Layer
Topics discussed in this section:Topics discussed in this section:
OSI Model Physical Layer
PHYSICAL LAYER
Physical layer coordinates the functions required transmit a bit stream over a physical medium.
The physical layer is responsible for movements of individual bits from one hop (node) to the next.
PHYSICAL LAYER
Physical layer is concerned with the following: (deal with the mechanical and electrical
specification of the primary connections: cable, connector) Physical characteristics of interfaces and medium Representation of bits Data rate : transmission rate Synchronization of bits Line configuration Physical topology Transmission mode
OSI Model Data Link Layer
DATA LINK LAYER
The data link layer is responsible for moving frames from one hop (node) to the next.
DATA LINK LAYER
Major duties Framing Physical addressing Flow control Error control Access control
DATA LINK LAYER
Hop-to-hop (node-to-node) delivery