Topic 2: The Open System Interconnection (OSI) Model & Network Protocols.

Topic 2:

The Open System Interconnection (OSI) Model &

Network Protocols.

Topic Review...

This chapter will covered:

- How to describe the network communication using OSI model.

- Explaination of network protocols.

- Use addressing schemes forTCP/IP suite.

- Understand the network services.

OSI Model...

Figure 1

Layer 7APPLICATION

Layer 6PRESENTATION

Layer 5SESSION

Layer 4TRANSPORT

Layer 3NETWORK

Layer 2DATA LINK

Layer 1PHYSICAL

Functions of OSI Model... Physical Layer

- responsible for transmitting individual bits from one node to the next.

Data Link Layer

- responsible for transmitting frames from one node to the next.

Network Layer

- responsible for the delivery of packets from the original source to the final destination.

Transport Layer

- responsible for delivery of a message from one proccess to another.

Session Layer

- responsible for the establisment, management & termination of logical connections between two end users.

Presentation Layer

- responsible for translation, encryption, authentication & data compression.

Application Layer

- responsible for providing service to the user.

Data delivery through OSI Model...

SMTP

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Presentation

Session

Transport

Network

Data Link

Physical

Email Receiver

Cable 101011

Des. MAC

Des.IP

Sour.IP

Sour. MAC

SIP data

data datadata

Port = 25

Format data

Figure 2

Data Link Layer

The Structure of Data Packets & Frame...

Figure 3

Network Layer

Figure 4

Media Access Control (MAC) Address..

- MAC (Media Access Control) address is the unique hardware address that is installed to the network card by its manufacturer.

- It’s also called physical address.

- This address is commonly written as a sequence of 12 hexadecimal digits, such as 0C-0B-CD-34-54-A0. Valid hexadecimal characters are "0" to "9" and "A" to "F".

Figure 5

Ethernet: IEEE 802.3 Local Area Network (LAN)

protocols...Ethernet protocols refer to the family

of local-area network (LAN) covered by the IEEE 802.3.

IEEE 802.3 is a working group and a collection of IEEE standards produced by the working group defining the physical layer and data link layer's media access control (MAC) of wired Ethernet.

Four data rates are currently defined for operation over optical fiber and twisted-pair cables:

10 Mbps - 10Base-T Ethernet (IEEE 802.3)

100 Mbps - Fast Ethernet (IEEE 802.3u)

1000 Mbps - Gigabit Ethernet (IEEE 802.3z)

10-Gigabit - 10 Gbps Ethernet (IEEE 802.3ae).

Protocol Structure: The basic IEEE 802.3 Ethernet MAC Data Frame for 10/100Mbps Ethernet:

IEEE 802.3

7 1 6 6 246-

1500bytes

4

Preamble

Start-of-frame delimiter

Destination address

Source Address

Length Type

802.2 Header & Data

Frame check sequence

Figure 6

Network Protocol... A protocol is a set of rules that

governs the communications between computers on a network.

In order for two computers to talk to each other, they must be speaking the same language.

The OSI (Open Systems Interconnection) Reference Model defines seven layers of networking protocols.

OSI Layer Name Common Protocol

7 Application

6 Presentation

HTTP | FTP | SMTP | DNS

5 Session

4 Transport TCP SPX

3 Network IP IPX

2 Data Link Ethernet

1 Physical

OSI model related to common network protocols

Figure 7

Figure 7 - illustrates how some of the major protocols would correlate to the OSI model in order to communicate via the Internet:

-Ethernet (Physical/Data Link Layers)

-IP/IPX (Network Layer)

-TCP/SPX (Transport Layer)

-HTTP, FTP, Telnet, SMTP, and DNS (Session/Presentation/Application Layers)

Core Protocols of TCP/IP...

- Address Resolution Protocol (ARP)

- Internet Protocol (IP)

- Internet Control Message Protocol (ICMP)

- Internet Group Management Protocol (IGMP)

- User Datagram Protocol (UDP)

- Transmission Control Protocol (TCP)

Functions...Address Resolution Protocol (ARP)

- is a telecommunications protocol used for resolution of network layer addresses into link layer addresses, a critical function in multiple-access networks.

Internet Protocol (IP)

-Responsible for routing packets across network boundaries, it is the primary protocol that establishes the Internet.

Internet Control Message Protocol (ICMP)

- to report problems with the delivery of IP datagrams.

Internet Group Management Protocol (IGMP)

- to manage group memberships in local area networks. A multicast router should know all groups having members in the local area network.

User Datagram Protocol (UDP)

-Provides a datagram service that emphasizes reduced latency over reliability.

Transmission Control Protocol (TCP)

-TCP provides reliable, ordered delivery of a stream of bytes from a program on one computer to another program on another computer.

Introduction to TCP/IP..

The Transmission Control Protocol/Internet Protocol (TCP/IP) suite created by the Department of Defense (DoD)

- to ensure and preserve data integrity and maintain the communication.

TCP/IP and the DoD Model...

The DoD model is basically a condensed version of the OSI model – it's composed of four, instead of seven layers:

- Process/Application Layer

- Host-to-Host Layer

- Internet Layer

- Network Access Layer

Figure 8: The DoD and OSI Model

Application

Presentation

Session

Transport

Network Access

Data Link

Physical

Process/Application

Host-to-Host

Internet Network

DoD ModelDoD Model OSI Model

DoD Model

Process/Application layer – defines protocols for node-to-node application communication and also controls user-interface specifications.

Host-to-Host layer – defining the protocols for setting up the level of transmission service for applications.

Internet layer – designating the protocols relating to the logical transmission of packets over the entire network.

Network layer – monitors the data exchange between the host and the network.

Network Addressing...

Network addressing also called as network number & uniquely identifies each network.

Every machine on the network shares that network address as part as of its IP address.

Example:

IP address 172.16.30.56

Network address 172.16.x.x

Class A:

8 bits

8 bits

8 bits

8 bits

Network Host Host Host

Class A:

Network Network Host Host

Class A:

Network Network Network Host

Class A:

Class A:

Multicast

Research

Figure 9: Summary of the three classes of networks

Network Address Range...

Class Class bit Range Hosts

A N.H.H.H 0 0 ~ 127 16.7 millions

B N.N.H.H 10 128 ~ 191

65k

C N.N.N.H 110 192 ~ 223

254

Public IP Address...

An IP address is considered public if the IP number is valid.

Public IP addresses are used by servers (including those for Web sites and DNS servers), network routers or any computer connected directly to the Internet via a modem.

Private IP address...

Class Range

A 10.0.0.0 ~ 10.255.255.255

B 172.16.0.0 ~ 172.31.255.255

C 192.168.0.0 ~ 192.168.255.255

Binary to Hexadecimal ...

Binary Hexadecimal

0000 0

0001 1

0010 2

0011 3

0100 4

0101 5

0110 6

0111 7

1000 8

1001 9

1010 A

1011 B

1100 C

1101 D

1110 E

1111 F

Binary= 0, 1Decimal= 0–9Hexadecimal= 0–9, A-F

- to describe communication where a piece of information is sent from one point to another point. In this case there is just one sender, and one receiver.

Example: the standard unicast applications (http, smtp, ftp and telnet) which employ the TCP transport protocol.

Addressing : Unicast Address...

- to describe communication where a piece of information is sent from one point to all other points. In this case there is just one sender, but the information is sent to all connected receivers.

Example: the standard application (address resolution protocol (arp) )

Addressing : Broadcast Address...

- to describe communication where a piece of information is sent from one or more points to a set of other points. In this case there is may be one or more senders.

Example of an application which may use multicast is a video server sending out networked TV channels.

Addressing : Multicast Address...

Static/Manual

- Setting up IP configuration at Network

Connection properties

Dynamic/automatic

- Automatically received IP address from DHCP server

ADDRESSING METHODS....

Static IP Address

Advantages

- The two names (Windows name and DNS name) are the same as each other, and neither ever changes. Other clients may therefore reliably access your machine by its DNS name.

-easily accessible by non-Windows internet services.

Disadvantages

- You can't move your machine to a different subnet and expect it to work. You need to reconfigure it

Dynamic IP (DHCP) Address

Advantages

-IP configuration information gets automatically configured for client machine by the DHCP server.

-If we move our client machine to a different subnet, the client will send out its discover message at boot time and work as usual.

Disadvantages

- Machine name does not change when we get a new IP address. The DNS (Domain Name System) name is associated with your IP address and therefore does change. This only presents a problem if other clients try to access your machine by its DNS name.

Domain Name Service (DNS)...

Domain Name Service (DNS) is the service used to convert human readable names of hosts to IP addresses. Host names are not case sensitive and can contain alphabetic or numeric letters