Ccn Unit1 VTU Raghudathesh

8/20/2019 Ccn Unit1 VTU Raghudathesh

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COMPUTER COMMUNICATION NETWORK (VTU) - 10EC71

UNIT - 1

Layered tasks, OSI Model, Layers in OSI model, TCP/IP Suite, Addressing, Telephone and cable

networks for data transmission, Telephone networks, Dial up modem, DSL, Cable TV for data

transmission. 7 Hours

TEXT BOOKS:

1. Data Communication and Networking, B Forouzan, 4th Ed, TMH 2006.

2. Computer Networks, James F. Kurose, Keith W. Ross: Pearson education, 2nd

Edition,

2003.

3. Introduction to Data communication and Networking, Wayne Tomasi: Pearson education

2007.

Special Thanks To:Faculty (Chronological): Arun A Badiger (GMIT Davengere), Dr. Manjunath N (JNNCE

Shimoga), Harisha G C (GMIT Davangere), Suresha V Sathegala (KVGCE Sullia)

Students:

BY:

RAGHUDATHESH G P

Asst Prof

ECE Dept, GMIT

Davangere 577004Cell: +917411459249

Mail: [email protected]

Quotes:

Change is hard at first, messy in the middle and gorgeous at the last.

Forget what hurt you, but never forget what it taught you.

People change, love hurts, friends leave, things go wrong. But just remember that lifegoes on.

Effort is important but where to make an effort makes all the difference.

All my life I thought air was free, until I bought a bag of chips.

People won’t remember days but they remember the moments with you.

Unit 1 RAGHUDATHESH G P Asst Professor

Department of ECE raghudathesh.weebly.com Page No - 1

mailto:[email protected]






Introduction:

History:

We have migrated from industrial revolution (18th

century) to age of steam engine

(19th century), and to information gathering, processing and distribution (20

th

century).

In computer era, we have migrated from a single computer serving allorganizations to computer networks.

The word data refers to information presented in whatever form is agreed upon by the

parties creating and using the data.

Definition: Data communications are the exchange of data between two devices via some

form of transmission medium such as a wire cable.

Data communications and networking are changing the way we live.

Computer Communication Network (CCN) deals with four major concepts. They are

1. Data communications

2. Networking

3. Protocols and standards

4. Networking models.

Networks exist so that data may be sent from one place to another which is the basic

concept of data communications.

Data communications between remote parties can be achieved through a process called

networking.

Protocols and standards are vital to the implementation of data communications and

networking.

Protocol:

Protocols refer to the set of rules and regulations that govern data

communications.

The key elements of a protocol are:

Syntax:

It refers to the structure/format of the data, i.e., the order in which the data

must be presented.

Ex.: A simple protocol may expect the first 8 bits of data to be the address

of the sender, the second 8 bits to be the address of the receiver, and therest of the stream to be the message/date.

Semantics:

Semantics refers to the meaning of each section of bits. It specifies how a

particular bit pattern to be interpreted, and what action to be taken based

on the interpretation.

Ex.: does an address identify the route to be taken or is the final

destination of the message.

Timing:





Timing refers to two characteristics:

When the data should be sent and

How fast the data can be sent.

Ex.: if a sender produces a data at a rate of 1Mbps and the receiver can

process the date at a rate of only 0.5 Mbps, then the transmission will

overload the receiver and same data will be lost. Standard:

A standard is a protocol that has been adopted by vendors and manufacturers.

There are 2 types Data Communication standards:

de facto :

Standards that have not been approved by an organized body

but have been adopted as standard through widespread use.

These are originally established by manufacturer who seeks to

define the functionality of new product/technology.

de jure : Standards that have been legislated by an officially recognized

body.

Network models serve to organize, unify, and control the hardware and software

components of data communications and networking.

Network:

It is a combination of hardware and software that sends data from one location to

another.

The hardware consists of the physical equipment that carries signals from one

point of the network to another.

The software consists of instruction sets that make possible the services that we

expect from a network.

Computer networks are very complex object; hence it is partitioned into vertical

set of levels, each level called layer.

Perspective:

Network users: services that their applications need e.g., guarantee that each

message it sends will be delivered without error within a certain amount of time

Network designers: cost-eff ective design e.g., that network resources are

efficiently utilized and fairly allocated to diff erent users

Network providers: system that is easy to administer and manage e.g., that faults

can be easily isolated and it is easy to account for usage.

Advantages of Networking:

Resources Sharing like File Sharing, Peripheral Sharing, Software Sharing with

multi-user licenses.

Shared Internet Access

Calculations Distribution





Layered Tasks:

We use the concept of layers in our daily life.

Scenario: let us consider two friends who communicate through postal mail. The figure below

shows the steps in this task.

Figure: Tasks involved in sending a letter

The process of sending a letter to a friend would be complex if there were no services

available from the post office.

The task includes a sender, a receiver, and a carrier that transports the letter.

There is a hierarchy of tasks:

1. Higher Layer

2. Middle Layer and

3. Lower Layer.

Activities that take place at each layer at each side is described below:

At the Sender Site:

H igher Layer: the sender writes the letter, inserts the letter in an envelope, writes

the sender and receiver addresses, finally drops the letter in a mailbox. Middle Layer: the letter is picked up by a letter carrier and delivered to the post

office.

Lower l ayer: the letter is sorted at the post office; a carrier transports the letter.

On the Way:

The letter is then on its way to the recipient.

On the way to the recipient’s local post office, the letter may actually go through a

central office.





In addition, it may be transported by trunk, train, airplane, boat, and/or a

combination of these.

At the Receiver Site:

Lower L ayer: The carrier transports the letter to the post office.

Middle Layer: The letter is sorted and delivered to the recipient’s mailbox.

H igher Layer: the receiver picks up the letter, opens the envelope, and reads it. Each layer performs specific tasks and uses the services of the layer immediately

below it.

Layered networking model is advantageous because

1. Divides networking into less complex components

2. Enables programmers to specialize in a particular level

3. Allows upgrades to a specific layer without effecting other layers

4. Encourages interoperability

5. Allows for standardized interfaces

Definition:

Open System: It is a set of protocols that allows any two different systems to communicate

regardless of their underlying architecture.

The OSI Reference Models:

It was first introduced in the late 1970s.

It is expanded as Open Systems Interconnection model.

It was developed by International Standards Organization (ISO).

The Open Systems Interconnection (OSI) model is an ISO standard that covers all aspects

of network communications.

The purpose of the OSI model:

To show how to facilitate communication between different systems without

requiring changes to the logic of the underlying hardware and software.

The OSI model is not a protocol; it is a model for understanding and designing

a network architecture that is flexible, robust, and interoperable.

The OSI model is a layered framework for the design of network systems thatallows communication between all types of computer systems.

Advantages of Reference Models:

It divides the network communication process into smaller and simpler

components, thus aiding component development, design, and troubleshooting.

It allows multiple-vendor development through standardization of network

components.





It encourages industry standardization by defining what functions occur at each

layer of the model.

It allows various types of network hardware and software to communicate.

It prevents changes in one layer from affecting other layers, so it does not hamper

development.

The OSI model is composed of seven layers:1. Physical Layer

2. Data link Layer

3. Network Layer

4. Transport Layer

5. Session Layer

6. Presentation Layer and

7. Application Layer

The structure of seven layers in OSI model as shows figure below

Figure: Seven layers of the OSI model

Layered Architecture: Layers are designed based on identifying which networking functions had related uses

and collected those functions into discrete groups that became the layers.

The OSI model allows complete interoperability between networks.

The Each layer uses the services of the layer immediately below it.





Peer-to-Peer Processes:

Definition: Process in Layer x on one machine communicates with Process in layer x on

another machine called Peer-to-Peer Processes.

This communication is governed by an agreed-upon series of rules and conventions

called protocols.

Communication between machines is therefore a peer-to-peer process using the protocolsappropriate to a given layer, which is shown in figure below

Figure: The interaction between layers in the OSI model

Interfaces Between Layers:

Interface defines the information and services a layer must provide for the layer above it.

The passing of the data and network information down through the layers of the sending

device and backup through the layers of the receiving device is made possible by an

interface between each pair of adjacent layers.

Well defined interfaces and layer function provide modularity to a network.





Organizations of the layers (subgroup):

The seven layers can be thought of as belonging to three subgroups. They are:

Network support layers:

Includes Physical (layer1), Data link (layer2), Network (layer3).

These layers deal with the physical aspects of moving data from one

device to another which includes electrical specifications, physicalconnections, physical addressing, transport timing and reliability.

User support layers:

Includes Session (layer5), Presentation (layer6), Application (layer7)

These layers support interoperability among unrelated software systems.

Transport layer (L ayer 4):

Links the above two layers subgroups.

This layer ensures that what the lower layers have transmitted is in a form

which can be used by the upper layers.

The upper OSI layers are almost always implemented in software. The lower layers are combination of hardware and software, except for physical layer

which is mostly hardware.

Data flow mechanism in OSI model:

The figure below gives a view of data flow mechanism in OSI layers.

Fi gure: An exchange using the OSI model

The process starts at layer 7 then moves from layer to layer in descending, sequential

order.





At each layer, a header, or possibly a trailer, can be added to the data unit. Commonly,

the trailer is added only at layer 2.

When the formatted data unit passes through the physical layer (layer 1), it is changed

into a digital form i.e., electromagnetic signal and transported along a physical link.

The reverse process occurs in the receiver side and the message is again in a form

appropriate to the application and is made available to the recipient.

Encapsulation:

Encapsulation is a process where the data portion of a packet at level N-1 carries the

whole packet from level N.

Ex.: A packet including header and data at layer 7 is encapsulated in the packet at level 6

and the process continues in the layer below.

Layers in the OSI Model:

1. Physical Layer:

The physical layer is concerned with transmitting raw bits over a communication

channel.

It deals with the mechanical, electrical, timing interfaces of the primary connections like

cable, connectors etc. and the physical transmission medium, which lies below the

physical layer.

Figure: Physical layer

Physical layer is concerned with the following:

Physical characteristics of interfaces and medium:

This layer defines the characteristics of interfaces and transmission medium.

This layer also defines the type of transmission medium like Cable/wire, Radio

waves, Infrared, Fiber/glass.

Representation of bits:





Bits must be encoded into signals may be electrical, optical.

Specifies the type of encoding (binary encoding as voltages like Manchester

encoding method)

Data Rate:

Defines transmission rate i.e., number of bits transmitted per second.

Defines the bit duration.

Synchronization of bits:

Transmitter and receiver clocks may synchronized.

Line configuration:

Deals with connection of device to the medium like point to point or multi-point

configuration.

Physical Topology:

Defines how device are connected to form network.

Ex.: Ring, Bus, Mesh, star Topology.

Transmission mode:

Defines the direction of transmission between two devices.

Ex.: Simplex, half duplex, duplex.





2. Data link layer:

It transforms the physical layer, a raw transmission facility to a reliable link. It makes the

physical layer appear error-free to the upper layer i.e., network layer.

Figure: Data link layer

Major responsibilities of data link layer are:

Framing: Divides the stream of bits received from network layer into

manageable data units called frames.

Physical addressing: Adds a header to the frame to define the sender and/or

receiver of the frame.

Flow Control: If the receiver is slower than the transmitter data link imposes a

flow control mechanism to avoid overwhelming the receiver.

Error Control: Retransmission of damaged frames, recognition of duplicate

frames. Error control is performed by adding a trailer to the end of the frame.

Access Control: Specifies which device has to get control over the link at any

given time when two or more devices connected to the same link.

Figure: Network Interface card

Note: Type ipconfig/all at command prompt to check your system’s Mac address.





Hop-to-hop delivery:

Figure below hop-to-hop (node-to-node) delivery by the data link layer

Figure: Hop-to-Hop deliveries

As the figure above shows, communication at the Data Link layer occurs between two

adjacent nodes. To send data from A to F, three partial deliveries are made. First, the DLL at A sends a frame to the DLL at B (a router). Second, the data link layer

at B sends a new frame to the data link layer at E. Finally, the DLL at E sends a new

frame to the DLL at F.

Here the frames that are exchanged between the three nodes have different values in the

headers. The frame from A to B has B as the destination address and A as the source

address. The frame from B to E has E as the destination address and B as the source

address. The frame from E to F has F as the destination address and E as the source

address.





3. Network Layer:

This layer is responsible for source to destination delivery of individual packet may be

across multiple networks/links.

Figure: Network layer

Other responsibilities of network layer include:

Logical addressing:

Physical address used in data link layer handles addressing locally i.e., within the

network.

If the packet moves out of the network then network layer adds the header to the

packet coming from upper layer which specifies the address of the sender and the

receiver which are present on the different network.

Routing:

Various independent networks/links are interconnected to form a large

network/internetwork; packets are delivered to the destination through differentnetwork using routers/switches. This is one of the basic functions of the network

layer.

Figure below shows the source to destination delivery by the network layer.

Figure: Source-to-destination delivery





4. Transport Layer:

Responsible for process-to-process delivery of the entire message.

A process is an application program running on a host.

Transport layer ensures the whole message arrives intact and in order, overseeing both

error control and flow control at the source-to-destination level.

Figure below shows the relationship of the transport layer to the network and sessionlayers.

Figure: Transport layer

Some of the responsibilities of the transport layer include:

Service-point addressing:

Computers often run several programs at the same time.

The transport layer header includes a type of address called a service-point

address (or port address).

The network layer gets each packet to the correct computer; the transport

layer gets the entire message to the correct process on that computer.

Segmentation and reassembly:

A message is divided into transmittable segments, with each segment

containing a sequence number.

These numbers enable the transport layer to reassemble the message

correctly upon arriving at the destination and to identify and replace

packets that were lost in transmission.

Connection control:

The transport layer can be either connectionless or connection oriented. A connectionless transport layer treats each segment as an independent

packet and delivers it to the transport layer at the destination machine.

A connection oriented transport layer makes a connection with the

transport layer at the destination machine first before delivering the

packets. After all the data are transferred, the connection is terminated.

Flow control:

Here flow control at this layer is performed end to end rather than across a

single link.





Error control:

Error control at this layer is performed process-to-process rather than

across a single link.

The sending transport layer makes sure that the entire message arrives at

the receiving transport layer without error (damage, loss, or duplication).

Error correction is usually achieved through retransmission.

Figure below illustrates process-to-process delivery by the transport layer.

Figure: Reliable process-to-process delivery of a message

5. Session Layer:

The session layer is responsible for dialog control and synchronization.

Specific responsibilities of the session layer include:

Dialog control:

The session layer allows two systems to enter into a dialog.

It allows the communication between two processes to take place in either

half-duplex full-duplex mode.

Synchronization:

The session layer allows a process to add checkpoints, or synchronization

points, to a stream of data.

Figure below shows the relationship between the presentation layer and the application

and session layers.





Figure: Session layer

6. Presentation Layer:

The presentation layer is concerned with the syntax and semantics of the information

exchanged between two systems.

Specific responsibilities of the presentation layer are:

Translation:

Different computers use different encoding systems, presentation layer is

responsible for interoperability between these different encoding methods.

The presentation layer at the sender changes the information from its

sender-dependent format into a common format. The presentation layer at

the receiving machine changes the common format into its receiver-

dependent format.

Encryption:

It ensures privacy for carry sensitive information by sending the

information in other form.

Compression:

Data compression reduces the number of bits contained in the information.

It becomes particularly important in the transmission of multimedia such

as text, audio, and video.

Figure below shows the relationship between the presentation layer and the application

and session layers

Figure: Presentation layer





7. Application Layer:

The application layer enables the user, whether human or software, to access the network.

It provides user interfaces and support for services such as electronic mail, remote file

access and transfer, shared database management, and other types of distributed

information services.

Figure below shows the relationship of the application layer to the user and the presentation layer.

Figure: Application layer

The major duties of the application:

Network virtual terminal: Enable to user for remote login

File transfer, access, and management Mail services

Directory services

TCP/IP PROTOCOL SUITE:

The TCPIIP protocol suite was developed prior to the OSI model.

Layers in the TCP/IP protocol suite do not exactly match those in the OSI model.

The original TCP/IP protocol suite was defined as having four layers

1. Host-to-network

2. Internet

3. Transport

4. Application

Comparison of TCP/IP is compared to OSI is shown below





Figure: TCP/IP and OSI model Comparison

We can say that the host-to-network layer is equivalent to the combination of the physical

and data link layers.

The internet layer is equivalent to the network layer. The application layer is roughly doing the job of the session, presentation, and

application layers with the transport layer in TCP/IP taking care of part of the duties of

the session layer.

Thus, we assume that the TCPIIP protocol suite is made of five layers: physical, data

link, network, transport, and application.

The first four layers provide physical standards, network interfaces, internetworking, and

transport functions that correspond to the first four layers of the OSI model.

The three topmost layers in the OSI model, however, are represented in TCP/IP by a

single layer called the application layer.

TCP / IP PROTOCOL layers description:

Figure: TCP/IP Protocol Suit





1. Host-to-network:

Describes physical interface between PC/workstation and a transmission

medium/network.

At the physical and data link layers, TCPIIP does not define any specific protocol. It

supports all the standard and proprietary protocols.

A network in a TCP/IP internetwork can be a local-area network or a wide-area network.

2. Internet/network/IP layer:

Concerned with access to and routing data across a network for two end systems attached

to a network.

At the network layer TCP/IP supports the Internetworking Protocol.

Internetworking Protocol (IP): It is an unreliable and connectionless protocol-a best-

effort delivery service.

IP transports data in packets called datagram, each of which is transported separately.

Datagram’s can travel along different routes and can arrive out of sequence or be

duplicated.

IP does not keep track of the routes and has no facility for reordering datagram once they

arrive at their destination.

IP, in turn, uses four supporting protocols:

1. Address Resolution Protocol (ARP):

It is used to associate a logical address with a physical address.

ARP is used to find the physical address of the node when its Internet

address is known.

2. Reverse Address Resolution Protocol (RARP):

It allows a host to discover its Internet address when it knows only its

physical address.

It is used when a computer is connected to a network for the first time or

when a diskless computer is booted.

3. Internet Control Message Protocol (ICMP):

It is a mechanism used by hosts and gateways to send notification of

datagram problems back to the sender.

ICMP sends query and error reporting messages.

4. Internet Group Message Protocol (IGMP):

It is used to facilitate the simultaneous transmission of a message to a

group of recipients.





3. Transport Layer:

This layer was represented in TCP/IP by two protocols, TCP and UDP.

These protocols are responsible for delivery of a message from a process to another

process.

User Datagram Protocol (UDP):

It is a process-to-process protocol that adds only port addresses, checksum error control, and length information to the data from the upper layer.

Transmission Control Protocol (TCP):

It provides full transport-layer services to applications. It is a reliable stream

transport protocol. It gives connection-oriented: A connection must be established

between both ends services.

SCTP (Stream Control Transmission Protocol):

It provides support for newer applications such as voice over the Internet.

It is a transport layer protocol that combines the best features of UDP and TCP.

4. Application Layer:

The application layer in TCP/IP is equivalent to the combined session, presentation, and

application layers in the OSI model.

Contains the logic needed to support the various user applications.

Separate modules are required for each application.

Many protocols are defined at this layer, some of them are:

1. Hypertext Transfer Protocol (HTTP): enables the connection between a web

server and a client

2. Simple Mail Transfer Protocol (SMTP): An electronic mail (e-mail) allows

users to send mails across an internet.

3. File Transfer Protocol (FTP): Is a standard way to transfer files between

different machines. Needs FTP client program on computer.

4. Domain Naming System (DNS): Provides meaningful names like

achilles.mycorp.com for computers to replace numerical addresses like

123.45.67.89.

5. TELNET: A remote terminal emulation protocol that enables clients to log on to

remote hosts on the network.

6. Simple Network Management Protocol (SNMP): Used to remotely manage

network devices.





Comparison between OSI and TCP/IP Model:

Sl No OSI Model TCP/IP MODEL

1 Contains 7 Layers Contains 4 Layers

2Uses Strict Layering resulting in vertical

layers.

Uses Loose Layering resulting in horizontal

layers.

3

Supports both connectionless &

connection-oriented communication in

the Network layer, but only connection-

oriented communication in Transport

Layer.

Supports only connectionless communication

in the Network layer, but both connectionless

& connection-oriented communication in

Transport Layer.

4It distinguishes between Service,

Interface and Protocol.

Does not clearly distinguish between Service,

Interface and Protocol.

5

Protocols are better hidden and can be

replaced relatively easily as technology

changes.

Protocols are not hidden and thus cannot be

replaced easily.

6

OSI reference model was devised before

the corresponding protocols were

designed.

The protocols came first and the model was a

description of the existing protocols.





Addressing:

Four levels of addresses are used in an internet employing the TCP/IP protocols:

1. Physical Addressing

2. Logical Addressing

3. Port Addressing

4. Specific AddressingEach address is related to a specific layer in the TCPIIP architecture, as shown in the figure

below

Figure: Layers and Associated Address

1. Physical Address:

The physical address, also known as the link/MAC address, is the address of a node as

defined by its LAN or WAN. It is included in the frame used by the data link layer.

It is the lowest-level address.

A network adapter has a unique and permanent physical address.

The physical addresses have authority over the network (LAN or WAN).





The size and format of these addresses vary depending on the network.

Ex., Ethernet uses a 6-byte (48-bit) physical address that is imprinted on the network

interface card (NIC). LocalTalk (Apple), however, has a 1-byte dynamic address that

changes each time the station comes up.

Scenario: In Figure a node with physical address 10 sends a frame to a node with

physical address 87, The two nodes are connected by a link (bus topology LAN). At thedata link layer, this frame contains physical (link) addresses in the header. These are the

only addresses needed. The rest of the header contains other information needed at this

level. The trailer usually contains extra bits needed for error detection. As the figure

shows, the computer with physical address 10 is the sender, and the computer with

physical address 87 is the receiver. The data link layer at the sender receives data from an

upper layer. It encapsulates the data in a frame, adding a header and a trailer. The header,

among other pieces of information, carries the receiver and the sender physical (link)

addresses. Note that in most data link protocols, the destination address, 87 in this case,

comes before the source address (10 in this case).

Figure: Physical addresses

Most local-area networks use a 48-bit (6-byte) physical address written as 12hexadecimal digits; every byte (2 hexadecimal digits) is separated by a colon, as shown

below:

07:01:02:01:2C:4B

In order to find the physical/link/MAC address of your system go to command prompt

and type ipconfig/all, the following information will be displayed as shown below





Figure: ipconfig/all

2. Logical Addresses:

Logical addresses are necessary for universal communications that are independent of

underlying physical networks.

Physical addresses are not adequate in an internetwork environment where different

networks can have different address formats.

A universal addressing system is needed in which host can be identified uniquely;

regardless of the underlying physical network hence we use logical addressing.

The logical addresses are designed for this purpose. A logical address in the Internet is

currently a 32-bit address that can uniquely define a host connected to the Internet.

No two publicly addressed and visible host on the Internet can have the same IP address.

This works in Layer-3 of OSI Model.

This would be generally referred as the IP address.





Scenario: Figure below shows a part of an internet with two routers connecting three

LANs.

Each device has a pair of addresses (logical and physical) for each connection. In this

case, each Computer is connected to only one link and therefore has only one pair of

addresses. Each router, however, is connected to three networks (only two are shown in

the figure). So each router has three pairs of addresses, one for each connection. The physical addresses will change from hop to hop, but the logical addresses usually remain

the same.

Figure: IP addresses

In order to find the logical/IP address of your system go to command prompt and type

ipconfig/all, the following information will be displayed as shown below





Figure: ipconfig/all

3. Port Addresses:

Port address is transport layer ID (similar to IP in Network Layer) which identify the

application on the host.

The IP address and the physical address are necessary for a quantity of data to travel from

a source machine to the destination machine/host.

However, arrival at the destination host is not the final objective of data communications

on the Internet. A system that sends nothing but data from one computer to another is not

complete.

Today, computers are devices that can run multiple processes at the same time.

The end objective of Internet communication is a process communicating with another

process.

Ex: computer A can communicate with computer C by using TELNET. At the same time,

computer A communicates with computer B by using the File Transfer Protocol (FTP).





Thus, for these above processes to receive data simultaneously, we need a method to

label the different processes. In other words, they need addresses.

In the TCP/IP architecture, the label assigned to a process is called a port address.

A port address in TCP/IP is 16 bits in length represented by one decimal number like

753.

Scenario: Figure below shows two computers communicating via the Internet. Thesending computer is running three processes at this time with port addresses A, B, and c.

The receiving computer is running two processes at this time with port addresses j and K.

Process A in the sending computer needs to communicate with process J in the receiving

computer.

Note: although physical addresses change from hop to hop, logical and port addresses

remain the same from the source to destination.

Figure: Port addresses

The port numbers are divided into three ranges:

1. Well-known ports.

2. Registered ports.

3. Dynamic/private ports.

In your machine Port number is seen as below





Figure: Port number in a machine

4. Specific Addresses:

Some applications have user-friendly addresses that are designed for that specific

address.

Ex.:

1. e-mail address : [email protected] and

2. The Universal Resource Locator (URL) : www.gmit.info.

The first defines the recipient of an e-mail; the second is used to find a document on the

World Wide Web.

These addresses, however, get changed to the corresponding port and logical addresses

by the sending computer.



http://www.gmit.info/






Telephone Network:

Introduction:

The telephone network had its beginnings in the late 1800s.

Telephone networks were originally created to provide voice communication.

Telephone networks use circuit switching.

The entire network, which is referred to as the plain old telephone system(POTS), was originally an analog system using analog signals to transmit voice.

With the advent of the computer era, the network, in the 1980s, began to carry

data in addition to voice.

During the last decade, the telephone network has undergone many technical

changes. The network is now digital as well as analog.

Major Components:

The telephone network, as shown in figure below

Figure: Telephone system

The telephone network shown in figure above has made three major components:

Local Loops:

A twisted-pair cable that connects the subscriber telephone to the nearest end

office or local central office.

Its B.W is 4 kHz for voice communication.

The first three digits of a local telephone number define the office, and the

next four digits define the local loop number.

Trunks:

These are transmission media that handle the communication between offices.

Trunk normally handles hundreds or thousands of connections through

multiplexing.

Transmission is usually through optical fibers or satellite links.

Switching Offices:

To avoid having a permanent physical link between any two subscribers, the

telephone company has switches located in a switching office.

Switch connects several local loops or trunks and allows a connection

between different subscribers.





Local-Access Transport Areas (LATAs):

A LATA can be a small or large metropolitan area.

A small state may have one single LATA; a large state may have several LATAs.

A LATA boundary may overlap the boundary of a state or part of a LATA can be in one

state, part in another state.

There are two types of LATAs Services like:1. Intra-LATA Services

2. Inter-LATA Services

Intra-LATA Services:

The services offered by the common carriers (telephone companies) inside a LATA are

called intra-LATA services.

The carrier that handles these services is called a local exchange carrier (LEC).

Before the Telecommunications Act of 1996 intra-LATA services were granted to one

single carrier. This was a monopoly.

After 1996, more than one carrier could provide services inside a LATA.

The carrier that provided services before 1996 owns the cabling system (local loops) and

is called the Incumbent Local Exchange Carrier (ILEC).The new carriers that can provide

services are called Competitive Local Exchange Carriers (CLECs).

CLECs would provide other services such as mobile telephone service, toll calls inside a

LATA, and so on. Communication inside a LATA is handled by end switches and

tandem switches.

A call that can be completed by using only end offices is considered toll-free. A call that has to go through a tandem office (intra-LATA toll office) is charged.

Figure: Switching offices in a LATA





Inter-LATA Services:

The services between LATAs called Inter-LATA Services.

These services handled by Interexchange Carriers (I X Cs).I X Cs sometimes called long-

distance

Companies, provide communication services between two customers in different LATAs.

Major companies providing inter-LATA services include AT&TMCI, WorldCom, Sprint,Verizon etc.

The I X Cs are long-distance carriers that provide general data communications services

including

Telephone service.

A telephone call going through an IXC is normally digitized, with the carriers using

several types of networks to provide service.

Each IXC that wants to provide inter LATA services in a LATA must have a POP in that

LATA. The LECs that provide services inside the LATA must provide connections so

that every subscriber can have access to all POPs.

Points of Presence (POP): Point of presence (POP) connects several LECs and IXCs.

Figure: Point of Presences (POPs)

Signaling:

Every communications system transmits data and control signals. The data are the reason

for the transmission in the first place, and the control signals start, stop and manage the

session.

Definition: Signaling is used for the establishment and control of a telecommunication

circuit, it also used for the management of the network, in contrast to the user information

transfer.

Types:

1. In Band Signaling:





When the data and control signals are transmitted within the same channel

or frequency, the signaling is said to be In-Band.

Voice path is established when the call setup is complete, using the same

path that the call setup signals used.

Ex.: An analog modem transmits control signals and data in the same

human voice frequency band2. Out band Signaling:

When control signals reside in a channel separate from the data, they are

known as out-of-band signals.

Voice trunks are used only when a connection is established, not before.

Faster call Setup.

Ex.: In ISDN service, the D channel is a dedicated channel for control

signals, and the B channels carry the data.

The traditional SS7 telephone system uses an entirely separate network for control

signals.1. Some of the other task performed by the signaling system includes:

2. Providing dial tone, ring tone, and busy tone

3. Transferring telephone numbers between offices

4. Maintaining and monitoring the call

5. Keeping billing information

6. Maintaining and monitoring the status of the telephone network equipment

7. Providing other functions such as caller ID, voice mail, and so on

The tasks of data transfer and signaling are separated in modern telephone networks: data

transfer is done by one network, signaling by another shown by the figure below:

Figure: Data transfer and signaling networks

In the above figure, different components are described below:

Data Transfer Network:





The data transfer network that can carry multimedia information today is a

circuit-switched network, although it can also be a packet-switched

network.

Signaling Network:

The signaling network is a packet-switched network involving the layers

similar to those in the OSI model or Internet model. The user telephone or computer is connected to the signal points (SPs). The link

between the telephone set and SP is common for the two networks.

The signaling network uses nodes called signal transport ports (STPs) that receive

and forward signaling messages.

The signaling network also includes a service control point (SCP) that controls the

whole operation of the network.

Other systems such as a database center may be included to provide stored

information about the entire signaling network.

Signaling System Seven (SS7):

SS7 is a global standard for telecommunications defined by the ITU.

The protocol that is used in the signaling network is called Signaling System Seven

(SS7).

The standard defines the procedures and protocol by which network elements in PSTN

exchange information over a digital signaling network to effect wireless (cellular) and

wire line call setup, routing and control. The SS7 network and protocol are used for:

1. Basic call setup, management and tear down.

2. Wireless services such as personal communications services (PCS), wireless

roaming, and mobile subscriber authentication.

3. Local Number Portability (LNP).

4. Toll-free (800/888) and toll (900) wireline services.

5. Enhanced call features such as call forwarding, calling party name/number

display, and three-way calling.

6. Efficient and secure worldwide telecommunications.

Layers of SS7:

It is very similar to the five-layer Internet model, but the layers are named

differently as shown below





Upper layer

Network Layer

Data link Layer

Physical Layer

Here,

MTP = Message Transfer Part

SCCP = Signaling Connection Control PartTCAP = Transaction Capabilities Application Port

TUP = telephone User Port

ISUP = ISDN User Port

Figure: Layers in SS7

Layers of SS7 are described as below:

Physical Layer (MTP Level 1): The physical layer in SS7 called message

transport part (MTP) level I uses several physical layer specifications such as T-l

(1.544 Mbps) and DCa (64 kbps). Data Link Layer (MTP Level 2): the MTP level 2 layers provides typical data

link layer services

Such as packetizing, using source and destination address in the packet header,

and CRC for error checking.

Network Layer (MTP Level 3): The MTP level 3 layer provides end-to-end

connectivity by using the datagram approach to switching. Routers and switches

route the signal packets from the source to the destination.





Transport Layer (SCCP): The signaling connection control point (SCCP) is

used for special services such as SaO call processing.

Upper Layers: TUP, TCAP, and ISUP are three protocols at the upper layers.

Telephone user port (TUP) is responsible for setting up voice calls. It

receives the dialed digits and routes the calls.

Transaction capabilities application port (TCAP) provides remote calls

that let an application program on a computer invoke a procedure on

another computer.

ISDN user port (ISUP) can replace TUP to provide services similar to

those of an ISDN network.

Services Provided by Telephone Networks:

Telephone companies provide two types of services: Analog and Digital.

Analog Services Include:

1.

Analog Switched Services:

This is dial up service, signal is of analog and the bandwidth is of between

0 to 4000 Hz.

Service is normally provided for a flat monthly rate or charged for each

call or a set of call.

2. 800 services:

If a subscriber needs to provide free connections for other subscribers

(customers) it requests the 800 service.

The call is free for the caller, but is paid by the callee (Tollfree).

3.

Wide area telephone service (WATS):

Outbound call (to the customer) paid by the organization, charges are

based on the number of calls.

4. 900 Service:

Inbound service, call is paid by the caller and is normally more expensive

than a normal call.

5. Analog Leased Service:

Customer can use leased line called a dedicated line which is permanently

connected to another customer.

Connection passes through the switches in the network, but switch is

always closed, no dialing is needed.

Digital Services:

1. Switched /56 Service:

Digital version of an analog switched line.

Provides data rate up to 56kbps.

Subscribers do not need modems need a device called a digital service unit

(DSU).





Modem Standards:

Most popular modems available are based on the V-series standards published by the

ITU-T they are:

1. V.32 modem:

It uses a combined modulation and encoding technique called trellis-coded

modulation. The V.32 calls for 32-QAM with a baud rate of 2400.

Uses 4 bits of each symbol represent data and 1 bit for error detection; then total

data rate is 4 x 2400 = 9600 bps.

The constellation diagram and bandwidth are shown in Figure below

Figure: The V.32 constellation and bandwidth

2. V.32bis Modem:

It was the first of the ITU-T standards to support 14,400-bps transmission.

It uses 128-QAM transmission (7 bits/baud with 1 bit for error control) at a rate of

2400 baud (2400 x 6 = 14,400 bps.)

The constellation diagram and bandwidth are shown in Figure below

Figure: The V.32bis constellation and bandwidth

3. V.34bis Modem:

It provides a bit rate of 28,800 with a 960-point constellation

Bit rate of 33,600 bps with a 1664-point constellation





4. V.90 Modem:

V.90 modems with a bit rate of 56,000 bps. Also called 56K modems.

These modems may be used only if one party is using digital signaling

They are asymmetric in that the downloading rate is a maximum of 56 kbps,

while the uploading rate can be a maximum of 33.6 kbps.

Figure: Uploading and downloading in 56K modems

5. V.92 Modem:

The standard above V90 is called V.92.

These modems can adjust their speed, and if the noise allows, they can upload

data at the rate of 48 kbps. The downloading rate is still 56 kbps.

Digital Subscriber Line (DSL):

After traditional modems reached their peak data rate, telephone companies developed

another technology, Digital subscriber Line DSL, to provide higher-speed access to the

Internet.

Digital subscriber line (DSL) technology is one of the most promising for supporting

high-speed digital communication over the existing local loops.

DSL technology is a set of technologies, each differing in the first letter namely:

1. Asymmetric Digital Subscriber Line (ADSL):





It is like a 56K modem, provides higher speed in the downstream direction than in

the upstream direction. That is the reason it is called ‘asymmetric’.

ADSL specifically divided the available bandwidth of the local loop unevenly for

the residential customer. The service is not suitable for business customers who

need a large bandwidth in both directions.

The existing local loops can handle bandwidths up to 1.1 MHz the entire 1.1 MHz

is available for data and voice communications.

ADSL is an adaptive technology. The system uses a data rate based on the

condition of the local loop line.

1.1 Discrete Multitone Technique (DMT):

The modulation technique that has become standard for ADSL is called the

Discrete Multitone Technique (DMT) which combines QAM and FDM as shown

below

Figure: Discrete Multitone Technique

There is no set way that the bandwidth of a system is divided. Each system can

decide on its Bandwidth division. Figure below shows Bandwidth division in

ADSL

Figure: Bandwidth division in ADSL





Typically, an available bandwidth of 1.104 MHz is divided into 256 channels.

Each channel uses a bandwidth of 4.312 kHz.

The figure above shows how bandwidth can be divided into the following:

Voice: Channel 0 is reserved for voice communication.

Idle: Channels 1 to 5 are not used and provide a gap between voice and data

communication.

Upstream data and control: Channels 6 to 30 (25 channels) are used for upstream

data transfer (24 channels) and 1 control.

If there are 24 channels, each using 4 kHz (out of 4.312 kHz available) with QAM

modulation. Upstream Data rate 24 x 4000 x 15, or a 1.44-Mbps.

But the data rate is normally below 500 kbps because some of the carriers are

deleted at frequencies where the noise level is large.

Downstream data and control: Channels 31 to 255 (225 channels) are used for

downstream data transfer and control. One channel is for control, and 224

channels are for data.

If there are 224 channels, then the data rate up to 224 x 4000 x 15, or13.4 Mbps.

But in practice data rate is normally below 8 Mbps, due to high noise in the some

channel.

1.2 ADSL Implementation: Customer Site: ADSL Modem (down link):

ADSL modem is located in customer site, like home or office buildings. This is

shown in figure below

Figure: ADSL modem

ADSL modem installed at a customer's site. The local loop connects to a splitter which separates voice and data

communications.

The ADSL modem modulates and demodulates the data, using DMT, and creates

downstream and upstream channels.





1.3 Telephone Company Site: DSLAM (uplink):

Figure: DSLAM

At the telephone company site, device is called a digital subscriber line access

multiplexer (DSLAM), is installed; it packetizes the data to be sent to the Internet.

Its function is similar to ADSL modem, and in addition it packetizes the data to be

sent to the Internet (ISP server)

1.4 ADSL Lite:

It is a splitter less ADSL, since the installation of splitters at the border of the user

premises expensive and impractical.

This technology allows an ASDL Lite modem to be plugged directly into a

telephone jack and connected to the computer.

The splitting is done at the telephone company. It uses 256 DMT carriers with 8-

bit modulation.

It can provide a maximum downstream data rate of 1.5 Mbps and an upstream

data rate of 512 kbps.

2. High-bit-rate Digital Subscriber Line (HDSL):

It was designed as an alternative to the T-1 line.

HDSL uses 2B1Q encoding which is less susceptible to attenuation.

A data rate of 1.544 Mbps can be achieved without repeaters up to a distance of 12,000 ft

(3.86 km).

HDSL uses two twisted pairs (one pair for each direction) to achieve full-duplex

transmission.

3. Symmetric Digital Subscriber Line (SDSL).

The symmetric digital subscriber line (SDSL) is a one twisted-pair version of HDSL.





It provides full-duplex symmetric communication supporting up to 768 kbps in each

direction.

Although this feature meets the needs of most residential subscribers, it is not suitable for

residential subscribers that send and receive data in large volumes in both directions.

4. Very High bit-rate Digital Subscriber Line (VDSL): Used as an alternative to ADSL.

Uses coaxial, fiber optic, or twisted pair cable for short distances.

DMT modulation technique is used

Bit rates of 25 to 55 Mbps for downstream and 3.2 mbps for upstream.

Comparisons of DSL Technologies:

Cable TV Networks: The cable TV network started as a video service provider, but it has moved to the

business of Internet access. Two types

1. Traditional Cable Networks

2. Hybrid Fiber-Coaxial (HFC) Network

1. Traditional Cable Networks:

It was called community antenna TV (CATV) because an antenna at the top of a tall hill

or building received the signals from the TV stations and distributed them, via coaxial

cables, to the community.

Communication in the traditional cable TV network is unidirectional.

Figure below shows a schematic diagram of a traditional cable TV network.





Figure: Traditional cable TV networks

2. Hybrid Fiber-Coaxial (HFC) Network:

It is a second generation of cable networks.

The network uses a combination of fiber-optic and coaxial cable.

The transmission medium from the cable TV office to a box, called the fiber node, is

optical fiber; from the fiber node through the neighborhood and into the house is stillcoaxial cable. Figure below shows a schematic diagram of an HFC network.

Figure: Hybrid fiber-coaxial (HFC) network

The Regional Cable Head (RCH) normally serves up to 400,000 subscribers.

The RCHs feed the distribution hubs, each of which serves up to 40,000 subscribers.

Modulation and distribution of signals are done in the distribution hub; the signals are

then fed to the fiber nodes through fiber-optic cables.

The fiber node splits the analog signals so that the same signal is sent to each coaxial

cable. Each coaxial cable serves up to 1000 subscribers.

The use of fiber-optic cable reduces the need for amplifiers down to eight or less.

Communication in an HFC cable TV network can be bidirectional.





Cable TV for Data Transfer:

Cable companies are now competing with telephone companies for the residential

customer who wants high-speed data transfer.

Following concepts are need to be discussed:

1. Bandwidth.

2. Sharing.3. Cable Mode (CM) and Cable Mode Transmission System (CMTS) .

4. Data Transmission Schemes: Data Over Cable System Interface Specification

(DOCSIS).

1. Bandwidth:

The coaxial cable has a bandwidth that ranges from 5 to750 MHz (approx).

To provide Internet access, the cable company has divided this bandwidth into three

bands:

i. Video

ii. Downstream data.

iii. Upstream data bands.

Figure below shows the bandwidth division

Figure: Division of coaxial cable band by CATV

i. Downstream Video Band:

It occupies frequencies from 54 to 550 MHz.

Each TV channel occupies 6 MHz; this can accommodate more than 80 channels.

ii. Downstream Data Band:

It occupies the upper band, from 550 to 750 MHz

This band is also divided into 6-MHz channels.

Modulation Downstream data band uses the 64-QAM modulation technique. The theoretical downstream data rate is 30 Mbps.

iii. Upstream Data Band:

It occupies the lower band, from 5 to 42 MHz

This band is also divided into 6-MHz channels.

Upstream data are modulated using the QPSK modulation technique due to high noise.

Data Rate is 12 Mbps, upstream data can be sent at (2 bits/Hz x 6 MHz).





2. Sharing:

Both upstream and downstream bands are shared by the subscribers.

Upstream Sharing:

The upstream data bandwidth is 37 MHz.

Only six 6-MHz channels available in the upstream direction.

A subscriber needs to use one channel to send data in the upstream direction. The question is, "How can six channels be shared in an area with 1000, 2000, or

even 100, 000 subscribers?" The solution is timesharing.

Downstream Sharing:

The downstream band has 33 channels of 6 MHz.

A cable provider probably has more than 33 subscribers; therefore, each channel

must be shared between a group of subscribers.

3. Cable Mode (CM) and Cable Mode Transmission System (CMTS):

To use a cable network for data transmission, need two key devices:i. Cable Modem (CM)

ii. Cable Modem Transmission System (CMTS).

1. Cable Mode (CM):

Cable modems transfer data across local cable TV lines, toggling between analog

and digital signals with data transfer rates comparable to DSL.

The cable modem connects a computer to the cable company network through the

same coaxial cabling that feeds cable TV (CATV) signals to a television set.

Uses Coaxial TV cable

1 to 10 Mbps download speeds

Up to 2 Mbps upload speeds

Cable connects from NIC to a cable modem, which has an RJ-45 port

Many users connect a router to the cable modem to provide access to several PC’s

or other network devices.

It is installed on the subscriber premises. It is similar to an ADSL modem, as

shown in figure below

Figure: Cable modem (CM)





2. Cable Modem Transmission System (CMTS):

The cable modem transmission system (CMTS) is installed inside the distribution hub

by the cable company.

It receives data from the Internet and passes them to the combiner, which sends them

to the subscriber.

The CMTS also receives data from the subscriber and passes them to the Internet.

Figure below shows the location of the CMTS.

Figure: Cable modem transmission system (CMTS)





Problems:

1. Match the following to one or more layers of the OSI model:

a. Route determination – Network Layer

b. Flow control- Data Link Layer, Transport Layer

c. Interface to transmission media- Physical Layer d. Provides access for the end user- Application layer


a. Reliable process-to-process message delivery – Transport Layer

b. Route selection - Network Layer

c. Defines frames - Data Link Layer

d. Provides user services such as e-mail and file transfer- Application layer

e. Transmission of bit stream across physical medium - Physical Layer

3. Match the following to one or more layers of the OSl model:

a. Communicates directly with user's application program- Transport Layer

b. Error correction and retransmission - Transport Layer

c. Mechanical, electrical, and functional interface - Physical Layer

d. Responsibility for carrying frames between adjacent nodes - Data Link Layer


a. Format and code conversion services - Presentation Layer

b. Establishes, manages, and terminates sessions – session layer

c. Ensures reliable transmission of data - Data link and transport layers

d. Log-in and log-out procedures - session layer

e. Provides independence from differences in data representation - Presentation Layer

5. If the data link layer can detect errors between hops, why do you think we need another

checking mechanism at the transport layer?

Solution:

The errors between the nodes can be detected by the data link layer control, but the error

at the node (between input port and output port) of the node cannot be detected by the data link

layer

6. Calculate the minimum time required to download one million bytes of information

using each of the following technologies:

a. V32 modem

b. V32bis modem

c. V90 modem





d. ADSL modem

e. Cable modem

Solution:

a. V.32 modem:

It has data rate of 9600bps

Minimum time required to down load = Size of Data / Data Rate= (10,00,000 / 9,600) Χ 8

= 834 seconds

= 13 min 54 sec

b. V.32 bis modem:

It has data rate of 14,400 bps

Minimum time required to down load = Size of Data / Data Rate

= (10,00,000 / 14,400) Χ 8

= 556 seconds= 9 min 16 sec

c. V.90 modem:

It has data rate of 56,000 bps


= (10,00,000 / 56,000) Χ 8

= 143 seconds

= 2 min 23 sec

d. ADSL modem:

It has data rate of 13.4 MbpsMinimum time required to down load = Size of Data / Data Rate

= (10,00,000 / 13.4 Χ 106) Χ 8

= 0.596 seconds

e. Cable TV modem:

It has data rate of 30 Mbps


= (10,00,000 / 30 Χ 106) Χ 8

= 0.266 seconds





Question Bank :

1. List the layers of the Internet model.

2. Which layers in the Internet model are the network support layers?

3. Which layer in the Internet model is the user support layer?

4. What is the difference between network layer delivery and transport layer delivery?5. What is a peer-to-peer process?

6. How does information get passed from one layer to the next in the Internet model?

7. What are headers and trailers, and how do they get added and removed?

8. What are the concerns of the physical layer in the Internet model?

9. What are the responsibilities of the data link layer in the Internet model?

10. What are the responsibilities of the network layer in the Internet model?

11. What are the responsibilities of the transport layer in the Internet model?

12. What is the difference between a port address, a logical address, and a physical address?

13. Name some services provided by the application layer in the Internet model.14. How do the layers of the Internet model correlate to the layers of the OSI model?

15. How are OSI and ISO related to each other?


17. What are the three major components of a telephone network?

18. Give some hierarchical switching levels of a telephone network.

19. What is LATA? What are intra-LATA and inter-LATA services?

20. Describe the SS7 service and its relation to the telephone network.

21. What are the two major services provided by telephone companies in the United States?

22. What is dial-up modem technology? List some of the common modem standards and

their data rates.

23. What is DSL technology? What are the services provided by the telephone companies

using DSL? Distinguish between a DSL modem and a DSLAM.

24. Compare and contrast a traditional cable network with a hybrid fiber-coaxial network.

25. How data transfer is achieved using CATV channels?

26. Distinguish between CM and CMTS.

27. Why circuit-switching was chosen for telephone networks?

28. Define end-to-end addressing in a telephone network when two parties communicate.

29. When we have an overseas telephone conversation, we sometimes experience a delay.

Give the reason?

30. Draw a bar chart to compare the different downloading data rates of common modems.

31. Draw a bar chart to compare the different downloading data rates of common DSL

technology implementations (use minimum data rates).

32. Calculate the minimum time required to download one million bytes of information using

each of the following technologies:

a. V32 modem





b. V32bis modem

c. V90 modem

33. Repeat Exercise 17 using different DSL implementations (consider the minimum rates).

34. Repeat Exercise 17 using a cable modem (consider the minimum rates).

35. What type of topology is used when customers in an area use DSL modems for data

transfer purpose?

VTU Question:

1. Show the layer representation in the TCP/IP model and the OSI model and explain. (Jan

2010, 10 M)

2. Give a brief overview of SS7 signaling. (Jan 2010, 10 M)

a. Match the following functions to the appropriate layers in the OSI model.

b. Dividing the transmitted bit stream into frames

c. Determining the route to be used through the subnetd. Reliable process to process message delivery

e. Format and code conversion services

f. Accessing the World Wide Web (Jan 2010, 10 M)

3. Explain OSI model, with a neat diagram. Consider a source, destination machine and

some intermediate nodes for discussion. (June 2010, 10 M)

4. How addresses employed (used) in internet employing TCP/IP protocol can be classified?

5. (June 2010, 02 M)

6. What is DSL technology? List different DSL’s available. Discuss salient feature of

ASDL. (June 2010, 08 M)

7. What are the levels of addresses that are used in internet, employing the TCP/IP

protocols? (December 2010, 10 M)

8. What are different types of services provided by telephone networks? (December 2010,

10 M)

9. Name the major components of a telephone network. (December 2010, 04 M)

10. With a neat diagram, explain the TCP/IP reference model, giving a brief description of

the protocols in each layer (July 2011, 10 M)

11. Differentiate between CM and CMTS. (July 2011, 04 M)

12. Explain the operation of ADSL using discreet multi one modulations indicating the

different channels, with a neat diagram. (July 2011, 06 M)

13. Explain the difference between OSI reference model and TCP/IP reference model

(December 2011, 05 M)

14. Match the following to one or more layers in OSI model:

a. Route determination

b. Flow control

c. Interface to transmission media





d. Provides access for end user

e. Format and code conversion services (December 2011, 05 M)

15. What is DSL technology? What are the services provided by the telephone companies

using DSL? Distinguish between DSL and DSLAM (December 2011, 10 M)

16. Describe the ISO OSI reference model of a computer network. Discuss the function of

each layer. (December 2012, 10 M)17. Describe the SS7 service and its relation to the telephone network. (December 2012, 05

M)

18. Distinguish between a DSL modem and a DSLAM. (December 2012, 05 M)

19. Explain briefly with relevant examples, the 4 levels of address that are used in an internet

employing the TCP/IP Protocols. (July 2013, 10 M)

20. Briefly describe the function of physical layer and data link layer. (July 2013, 06 M)

21. Explain the operation of ADSL using Discrete Multitone Technique indicating the

different channels with diagram. (July 2013, 04 M)

22. How do the layers of TCP/IP model correlate to the OSI model?(January 2014, 08M)23. Explain about IxCs with a schematic. What are point of presence?( January 2014, 06M)

24. How ADSL could achieve higher data rate over existing local loops? Explain DSLAM. (

January 2014,06M)


Ccn Unit1 VTU Raghudathesh

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