Connectionless and Connection-Oriented Services

Connection-less and Connection-Oriented Services

When an application uses the connection-oriented service, the client and the

server send control packets to each other before sending packets with real

data (such as e-mail messages). This so-called handshaking procedure

alerts the client and server, allowing them to prepare for flowing of packets.

Once the handshaking procedure is finished, a "connection" is said to be

established between the two end systems.

Example: TCP

TCP three-way handshake

TCP three-way handshake

Connectionless Service

There is no handshaking with the Internet's connectionless service.

When one side of an application wants to send packets to another side

of an application, the sending application simply sends the packets.

Since there is no handshaking procedure prior to the transmission of

the packets, data can be delivered faster.

UDP (User Datagram Protocol)

But there are no acknowledgments either, so a source never knows for

sure which packets arrive at the destination.

Network Protocol

Network Protocol

A protocol defines the format and the order of messages exchanged

between two or more communicating entities, as well as the actions

taken on the transmission and/or receipt of a message.

A network protocol is similar to a human protocol, except that

the entities exchanging messages and taking actions are hardware

or software components of a computer network.

Network protocols

Network Edge

In computer networking jargon, the computers that we use on a daily basis

are often referred to as or hosts or end systems. They are referred to as

"hosts" because they host (run) application-level programs such as a Web

browser or server program, or an e-mail program.

They are also referred to as "end systems" because they sit at the "edge"

of the Internet.

Network edge

Connection-less and Connection-Oriented Services

Network Core

Packet Switching versus Circuit Switching

Network

Network

What is Network?

Network is a group of connected computers connected by

Cables or any other media.

Network

Application of Network

- Resource Sharing

Hardware ( computing resources,disks, printers ... )

Software (Application Software)

- Information Sharing

Easy accessibility from anywhere ( Files, Databases, ... )

Search Capability ( www )

- Communication

Email

Message broadcast

Internet

What is Internet?

A global network of interconnected networks is called Internet.

internet connection

Growth of Internet

internet use

1977: 111 hosts on Internet

1981: 213 hosts

1983: 562 hosts

1984: 1,000 hosts

1986: 5,000 hosts

1987: 10,000 hosts

1989: 100,000 hosts

1992: 1,000,000 hosts

2001: 150 – 175 million hosts

2002: over 200 million hosts

Now (2016) , about 3,424,971,237 population of the planet are on the Internet

Network and Internet

How to differentiate Network from Internet?

network and internet

We can have network without Internet !

Internet is meaningless without network !

lan

Network Categories

LAN (Local Area Network) :

- Operate within a limited geographic area

- Allow many users to access high-bandwidth media

- Provide full-time connectivity to local services

- Connect physically adjacent devices

MAN (Metropolitan Area Network) :

- Interconnect users in a geographic area or region larger than

area covered by LAN but smaller than the area covered by a WAN

- Connect networks in a city into a single larger network

man

wan

WAN (Wide Area Network :

- Operate over large, geographically separated areas

- Provide full-time remote resources

connected to local services

- Provide e-mail, World Wide Web,

file transfer

WAN technologies e.g:

Modems

Network Data Transmission mode

Simplex :

simplex

Data can be transferred only one direction in medium

Example:

Radio: Just receives the signals

Remote Control of the TV.

Half-Duplex :

Data can be transferred both ways in the medium but in only one direction

half duplex

Example:

Wireless Radio

Full-Duplex :

Data can be Transferred in both directions simultaneously

full duplex

Example:

Telephone Communication

Network Data Transmission

Network connection Methods

Peer-to-Peer network :

Has no dedicated servers

There are no hierarchical differences between workstations in the network

All workstations are clients and servers at the same time

peer to peer

Client / Server network :

- Server-based Network has become the standard model for

networking

- The server provides services which clients need in network

- Centrally manage the usage of resources

Advantages:

client/server

. Centralized Administration

. Security and policy

applied by server

. Backup

. Monitoring

Network Devices

NIC (Network Interface Card)

NIC

- Interface for the computers to the network

- Each NIC has a unique hardware address

called MAC address (Physical address)

- connected to other network components

via a transmission media (e.g. cable)

Hub

- All incoming signal are passed to all ports

hub

- Attached devices divide the available

network bandwidth

Switch

- Intelligent HUB

switch

- Solves traffic problems

- Improves network performance

- Works with MAC Address

Repeater

– Receives electrical signals, amplifies them and passes them on

– Bidirectional signal amplification

– Enables long cable stretches

repeater

Bridge

- Connects separate two network segments

bridge

- Similar to repeater

- Addressing with the MAC Addresses

Router

router

- Connect networks

- Connects different networks which

work with the same protocols

- Important Information for routing

are stored in the Routing tables

- Contain IP Table

Network Topologies

BUS

- One cable connects multiple computers

- T-Connectors are used

- One computer can transmit data at a time

- A central cable (coaxial cable)

- All attached stations are affected by disturbance at the central cable

BUS

STAR

STAR

- All computers are connected

through central hub or Switch

- Each computer has separate cable

- Fault tolerance

- Most Used Topology

Mesh

- Each device/PC is connected to every

Mesh

other device/PC

- Each connection needs its own cable

- Highest fault tolerance

- Expensive topology

CN= Cable Needed , D = Device

CN = (D * (D-1)) / 2

OSI model and TCP stack

OSI model and TCP stack

ISO-OSI Model

OSI Overview

• ISO = International Organization for Standardization

• OSI = Open Systems Interconnection

• ISO-OSI Reference Model is a layered and abstract

description for computer communication

– Hardware independent

– Hierarchical

• Functionality is divided into seven protocol layers

– Each layer responds services form the superior layer

– Each layer issues services to the subordinate layer

– Each layer is transparent to the other layers

osi layers

Application Layer

• The seventh layer of the OSI model

• Interface for the network applications

• Issues requests to the presentation layer.

• Known protocols:

• DNS, DHCP

• FTP, HTTP

• POP3, IMAP, SMTP

• ...

Presentation layer

• The sixth layer of the OSI model

• Responds to service requests from the application layer

• Issues service requests to the session layer

• Delivery and formatting of informations

– Code transformation

(e.g. from ASCII, EBCDIC to ASN.1)

• Encryption and compression

• These tasks often get fulfilled by the application layer

Session Layer

• The fifth layer of the OSI model

• Responds to service requests from the

presentation layer

• Issues service requests to the transport layer.

• Controls the initialization, the execution and

The completion of the communication

connection

• E.g. HTTP sessions

Transport Layer

• The fourth layer of the OSI model

• Responds to service requests from the

session layer

• Issues service requests to the network layer

• End to end connection

• Error recovery and flow control

• Ensuring complete data transfer

• Port number

• known protocol:

• TCP, UDP

Network Layer

• The third level of the OSI model

• Responds to service requests from the transport

layer

• Issues service requests to the data link layer.

• Finding the way of the data packets

• Flow control, Overload protection and Debug

• IP address

Data Link Layer

• The second layer of the OSI model

• Responds to service requests from the network

layer

• Issues service requests to the physical layer

• Access to the physical net

• Controls the bit transmission

• MAC address

Physical Layer

• The first layer of the OSI model

• Performs services requested by the data link

layer

• Controls the sending and receiving of the

data bits

• Transforms the bits to electric,

electromagnetic and optic signals

• Defines period and clock cycles

OSI Reference Model

OSI Reference Model

TCP/IP Model

TCP/IP Model

Breaking cisco 2600 series password

Breaking cisco 2600 series password

----------------------
swith off the device and swith on
after 2 or 3 seconds press the CTRL+PauseBreak
!you will enter in the rom monitor mode which is the safe mode.
There is an entery by name of configuration register.
if the configuration register is 0x2102(default), it means to load the configuration file from the nvram when booting. we have to change the configuration register to 0x2142 which means to by pass the configurtion file from nvram.

rommon> confreg 0x2142
rommon> reset

when router boots,
Router#
copy startup-config running-config
!we copy the configuration file from nvram to running-config
change the passwords and configuration register number
you are done

conf t
enable password cisco
line con 0
password cisco
login
exit
line vty 0 4
password cisco
login

configuration-register 0x2102
exit
copy run star

-------------------------------
breaking 2500 series password
-------------------------------
swith off the device and swith on
after 2 or 3 seconds press the CTRL+PauseBreak
!you will enter in the rom monitor mode which is the safe mode.
There is an entery by name of configuration register.
if the configuration register is 0x2102(default), it means to load the configuration file from the nvram when booting. we have to change the configuration register to 0x2142 which means to by pass the configurtion file from nvram.
> o/r 0x2142
>init

copy startup-config running-config
!we copy the configuration file from nvram to running-config
change the passwords and configuration register number
you are done

conf t
enable password cisco
line con 0
password cisco
login
exit
line vty 0 4
password cisco
login

configuration-register 0x2102
exit
copy run star