Objectives: Chapter 1: Introduction Types of Networks OSI Reference Model (7 Layers) TCP/IP Model...

Objectives:

Chapter 1: Introduction

Types of Networks OSI Reference Model (7 Layers) TCP/IP Model Network Devices Network Topologies

Business Applications of Networks

A network with two clients and one server.

Business Applications of Networks (2)

The client-server model involves requests and replies.

Client/Server

In a client/server arrangement, network services are located on a dedicated computer called a server. The server responds to the requests of clients.

The client/server model of networking can be used to overcome the limitations of the peer-to-peer network.

Home Network Applications (2)

In peer-to-peer system there are no fixed clients and servers.

Peer-to-Peer Networks

In a peer-to-peer network, networked computers act as equal partners, or peers.

In a peer-to-peer network, individual users control their own resources.

The users may decide to share certain files with other users.

The users may also require passwords before allowing others to access their resources.

Network Hardware

• Local Area Networks

• Metropolitan Area Networks

• Wide Area Networks

• Wireless Networks

• Home Networks

Broadcast Networks (2)

Classification of interconnected processors by scale.

Network Types

- Local area networks (LANs), which connect over a relatively small geographical area, typically connecting computers within a single office or building. In most cases they connect to a common electronic connection – commonly known as a network backbone. LANs can connect to other networks either directly or through a WAN or MAN.

- Metropolitan area networks (MANs), which normally connect networks around a town or city based on cable TV. It is smaller than a WAN, but larger than a LAN.

- Wide area networks (WANs), which connect networks over a large geographical area, such as between different buildings, towns or even countries.

Local Area Networks

Two broadcast networks(a) Bus(b) Ring

Metropolitan Area Networks

A metropolitan area network based on cable TV.

Wide Area Networks

Relation between hosts on LANs and the subnet.

Wireless Networks

Categories of wireless networks:

• System interconnection

• Wireless LANs

• Wireless WANs

Network Software

• Protocol Hierarchies• Design Issues for the Layers• Connection-Oriented and Connectionless Services• Service Primitives• The Relationship of Services to Protocols

Protocol Hierarchies (2)

The philosopher-translator-secretary architecture.

Design Issues for the Layers

• Addressing• Error Control• Flow Control• Multiplexing• Routing

Connection-Oriented and Connectionless Services

Six different types of service.

• Flow Control

• Error checking and correction

Service Primitives

Five service primitives for implementing a simple connection-oriented service.

Service Primitives (2)

Packets sent in a simple client-server interaction on a connection-oriented network.

Services to Protocols Relationship

The relationship between a service and a protocol.

Reference Models

• The OSI Reference Model

• The TCP/IP Reference Model

• A Comparison of OSI and TCP/IP

• A Critique of the OSI Model and Protocols

• A Critique of the TCP/IP Reference Model

PhysicalPhysical

Data linkData link

NetworkNetwork

TransportTransport

SessionSession

PresentationPresentation

ApplicationApplication

PhysicalPhysical

Data linkData link

NetworkNetwork

TransportTransport

SessionSession


ApplicationApplicationA

A

A

A

A

A

P

P

P

P

P

S

S

S

S

T

T

T

N

ND D

Virtualdata flow

Actual data flow

Sender Receiver

OSI Model

PhysicalPhysical

Data linkData link

NetworkNetwork

TransportTransport

SessionSession



PhysicalPhysical

Data linkData link

NetworkNetwork

TransportTransport

SessionSession



A

A

A

A

A

P

P

P

P

P

S

S

S

S

T

T

T

N

ND D

Virtualdata flow

Actual data flow

Sender Receiver

PhysicalPhysical

Data linkData link

NetworkNetwork

TransportTransport

SessionSession



PhysicalPhysical

Data linkData link

NetworkNetwork

TransportTransport

SessionSession



PhysicalPhysical

Data linkData link

NetworkNetwork

TransportTransport

SessionSession



A

A

A

A

A

P

P

P

P

P

S

S

S

S

T

T

T

N

ND D

Virtualdata flow

Actual data flow

Sender Receiver

OSI 7-layered Model

OSI 7-layer Model (International Standards Organisation)Allow manufacturers of different systems to interconnect their equipment through standard interfaces. Allow software and hardware to integrate well and be portable on differing systems.Create a model which all the countries of the world use.

OSI 7-layer Model (International Standards Organisation)Allow manufacturers of different systems to interconnect their equipment through standard interfaces. Allow software and hardware to integrate well and be portable on differing systems.Create a model which all the countries of the world use.

Example layersPhysical/Data Link: Ethernet/FDDI/ISDN/etcNetwork: IP (Internet) or IPX (NetWare)Transport: TCP (Internet) or SPX (NetWare)Session-Application: HTTP/FTP/TELNET/SMTP/etc

Example layersPhysical/Data Link: Ethernet/FDDI/ISDN/etcNetwork: IP (Internet) or IPX (NetWare)Transport: TCP (Internet) or SPX (NetWare)Session-Application: HTTP/FTP/TELNET/SMTP/etc

OSI Layers

Transport. Provides for reliable end-to-end error and flow control. The network layer does not validate that the data packet has been successfully received, thus it is up to the transport layer to provide for error and flow control.Network. Defines the protocols that are responsible for delivering the data to the required destination.Data link. Provides for the access to the network media and thus builds on the physical layer. It takes data packets from the upper level and frames it so that it can be transmitted from one node to another. Physical. Defines the electrical characteristics of the communications channel and the transmitted signals, such as voltage levels, connector types, cabling, and so on.

Transport. Provides for reliable end-to-end error and flow control. The network layer does not validate that the data packet has been successfully received, thus it is up to the transport layer to provide for error and flow control.Network. Defines the protocols that are responsible for delivering the data to the required destination.Data link. Provides for the access to the network media and thus builds on the physical layer. It takes data packets from the upper level and frames it so that it can be transmitted from one node to another. Physical. Defines the electrical characteristics of the communications channel and the transmitted signals, such as voltage levels, connector types, cabling, and so on.

Application. Provides application pro grams, such as file transfer, print access and electronic mail.Presentation. Transforms the data into a form which the session layer and the application layer expect. It can perform encryption, translating character sets (such as converting binary values into text for transmitting a binary program over a text-based system), data compression and network redirections.Session. Setting up, maintaining and closing down of a session. It should not depend on any specific transport or network layer, and should be able to communicate as if the session was created on a stand-alone computer (that is, the network is transparent to the session layer).

Application. Provides application pro grams, such as file transfer, print access and electronic mail.Presentation. Transforms the data into a form which the session layer and the application layer expect. It can perform encryption, translating character sets (such as converting binary values into text for transmitting a binary program over a text-based system), data compression and network redirections.Session. Setting up, maintaining and closing down of a session. It should not depend on any specific transport or network layer, and should be able to communicate as if the session was created on a stand-alone computer (that is, the network is transparent to the session layer).

PhysicalPhysical

Data linkData link

NetworkNetwork

TransportTransport

SessionSession - Application

Data linkEthernet/ATM/FDDI

NetworkIP/IPX

TransportTCP/SPX

SessionHTTP/FTP

RouterRouter

RouterRouter

Data linklayer

Networklayer

Data stream

Transportlayer

ApplicationApplicationApplicationApplication


ApplicationApplicationApplicationApplication


MACaddressin NIC Network

address

Socket

Physicallayer

OSI Layers

Reference Models

The OSI reference model.

PDU: Protocol Data Unit

TCP/IP Model

The TCP/IP reference model.

Reference Models (3)

Protocols and networks in the TCP/IP model initially.

Architecture of the Internet

Overview of the Internet.

IEEE 802 Standards

The 802 working groups. The important ones are marked with *. The ones marked with are hibernating. The one marked with † gave up.

OSI Layer Devices

RepeaterRepeater

Network segment (repeater extends the network segment)

RouterRouter

Bridge only forwards if thestation (or MAC) address is not on the connected network segment that it originated from. Broadcasts are also passed over.

BridgeBridge

Router only forwards if the network address is on anothernetwork. It does not forward broadcasts.

Network segment bounded by a router or a bridge

Repeaters, bridges, Switches and routers

Network TypesRouter

NetworkNetwork

Data LinkData Link

PhysicalPhysical A router routes with the network address (such as the IP address)

Data LinkData Link

PhysicalPhysical A bridge routes withthe MAC address

PhysicalPhysical A repeater boosts thesignal

Repeater

Bridge

Network / Physical topologies

Star Network

Centralserver

Star NetworkAdvantages:Since the data rate is relatively low between central server and the node, a low-specification twisted-pair cable can be used connect the nodes to the server. A fault on one of the nodes will not affect the rest of the network. Typically, mainframe computers use a central server with terminals connected to it.Disadvantages:Network is highly dependent upon the operation of the central server. If it were to slow significantly then the network becomes slow. In addition, if it were to become un-operational then the complete network would shut down.

Star NetworkAdvantages:Since the data rate is relatively low between central server and the node, a low-specification twisted-pair cable can be used connect the nodes to the server. A fault on one of the nodes will not affect the rest of the network. Typically, mainframe computers use a central server with terminals connected to it.Disadvantages:Network is highly dependent upon the operation of the central server. If it were to slow significantly then the network becomes slow. In addition, if it were to become un-operational then the complete network would shut down.

Bus network

Common bus

All computers have access toa common bus at the same time

Ethernet hub

Bus networkUses a multi-drop transmission medium.All nodes on the network share a common bus and all share communications. This allows only one device to communicate at a time. A distributed medium access protocol determines which station is to transmit. data frames contain source and destination addresses, where each station monitors the bus and copies frames addressed to itself.

Twisted-pair cables give data rates up to 100Mbps, whereas, coaxial and fibre optic cables give higher bit rates and longer transmission distances. Gigabit Ethernet is now available (1Gbps).

A typical bus network is Ethernet 2.0.

Bus networkUses a multi-drop transmission medium.All nodes on the network share a common bus and all share communications. This allows only one device to communicate at a time. A distributed medium access protocol determines which station is to transmit. data frames contain source and destination addresses, where each station monitors the bus and copies frames addressed to itself.

Twisted-pair cables give data rates up to 100Mbps, whereas, coaxial and fibre optic cables give higher bit rates and longer transmission distances. Gigabit Ethernet is now available (1Gbps).

A typical bus network is Ethernet 2.0.Advantages:Good compromise over the other two topologies as it allows relatively high data rates. If a node goes down, it does not affect the rest of the network.

Disadvantages:Requires a network protocol to detect when two nodes are transmitting at the same time. Does not cope well with heavy traffic rates.

Advantages:Good compromise over the other two topologies as it allows relatively high data rates. If a node goes down, it does not affect the rest of the network.

Disadvantages:Requires a network protocol to detect when two nodes are transmitting at the same time. Does not cope well with heavy traffic rates.

Token Ring (example data exchange)

ControlToken(a)

DataFrame(b)

ControlToken

(d)

Ack.A

D

C

B

(c)

Token RingControl token rotates round the ring.Node wishing to transmit data captures the token.Node captures token and transmits a data frame.Data frame rotates round network.All nodes read the frame and determine if the data is for them.Destination node reads the data, and sets an acknowledgement flag.Data frame continues round the network, until the source node receives it.Source node puts the control token back on the ring.

Token RingControl token rotates round the ring.Node wishing to transmit data captures the token.Node captures token and transmits a data frame.Data frame rotates round network.All nodes read the frame and determine if the data is for them.Destination node reads the data, and sets an acknowledgement flag.Data frame continues round the network, until the source node receives it.Source node puts the control token back on the ring.

Concentrator (or hub)

Concentrator (or hub)

Network backbone

Tree topology Tree topologyResources should be grouped logically when attached to hubs, such as local file servers, printers, and so on.

Advantages:Nodes local to a hub can communicate with each other without the data traffic going onto other network segments.A fault on a single computer or a hub does not bring the whole network down.Communication between the hub and the computer has relatively low data transfers, as opposed to the transfer connected hubs to hubs.Easy to connect and disconnect to.

Disadvantages:Network may suffer from slow data transfer if the network is not planned to reflect tree topology. Typically network is created with workgroups.

Most networking technologies now use hubs to connect to.Typically for Ethernet and Token Ring networks.

Tree topologyResources should be grouped logically when attached to hubs, such as local file servers, printers, and so on.

Advantages:Nodes local to a hub can communicate with each other without the data traffic going onto other network segments.A fault on a single computer or a hub does not bring the whole network down.Communication between the hub and the computer has relatively low data transfers, as opposed to the transfer connected hubs to hubs.Easy to connect and disconnect to.

Disadvantages:Network may suffer from slow data transfer if the network is not planned to reflect tree topology. Typically network is created with workgroups.

Most networking technologies now use hubs to connect to.Typically for Ethernet and Token Ring networks.

Workgroup- with printer- file server- etc

Objectives: Chapter 1: Introduction Types of Networks OSI Reference Model (7 Layers) TCP/IP Model...

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