An Introduction To Computer Networks

Published Date: 02 Nov 2017

Serial connection: Serial connection is used in many cases like in WAN technologies including in Asynchronous Transfer Mode (ATM), frame relay . Data transfer takes place one bit at a time. Serial connection can be done both in synchronous and asynchronous bit .

IP addressing: For every communication between the devices IP address plays an important role . IP address are of two types IPV4 and IPV6 . As IPV4 is of 32 bit and IPV6 is 128 bits more IP address are achieved from IPV6 protocol. The main task of subnet masking is to avoid the wastage of the IP address. As LAN cannot handle hundreds of host . The remaining IP address are lost, to avoid this problem subnet masking is done.connection between the routers and to ensure successful transmission the ping command is used. Last IP address in the network is used as broad cast address. IP In version 4 divided in 5 classes and default subnet mask is given for all the classes..

VLAN/Ethernet: Different users are connected to each other by repeaters or hub. By using this devices data collision can be decreased. As these device doesn't allow the collision in the network, the data rate will be very high ,and it also allows broadcast the data for the destination user who are connected in the network. As VLAN'S can provide domains, therefore the cost is decreased because the usage of routers is not there.

ROUTING INFORMATION PROTOCOL(RIP) Packets reaching from one device to other by following a route . This route is called as routing., this can be done in three ways static , dynamic and default routing. static routing is used in small network, and destination IP address is required. Dynamic routing changes routes Routing Information Protocol is used for transmission of packets dynamically ,it is used for small and large networks. RIP is a open standard protocol Administrative distance is 120.

SERIAL CONNECTIONS

1.1 INTRODUCTION

Serial connection is used in many cases WAN technologies including in Asynchronous Transfer Mode (ATM), frame relay . .

1.2 Working of serial connection: In serial connection data is transfer one bit at a time, over a bus or channel. Signal integrity and data rate speed can be achieved from the recent technology. Communication is done between the DTE and DCE devices our computer is DTE device modem is DCE device. RS232 is acts as interface between the DTE and DCE devices.

1.3 SYNCHRONOUS Data transfer

In synchronous Data transfer transmitter gets the acknowledgment from the receiver about the status of transfer data . If it is received it give a positive acknowledgment or else it sends the message to resend the data again line.. This ensures the transfer data in correct form between the sender and receiver. DB-60 andv.35 connecter. The serial interface is achieved by connecting Winchester- type to one end and DB-60 connector to another end .

Figure 1.2.i DB-60 Connector

Source http://www.misnetworks.co.uk/DB60%20to%20DB60.html

1.2.1 PARAMETERS IN PHYSICAL LAYER

Connections in WAN is made between DCE and DCTE. DTE us the user and DCE is considered as service provider. Every DCE node gives signal timing. To find the interface is DCE or DTE by using the command.

show controller serial <interface number>

CLOCK RATE: The data rate produnced in cycles per second . It also define as bit rate produced in a given time. The serial interface produce default bit rate up to 2Mbps,some serial interface also produce 52 Mbps. To change the default bit rate, the command used is

1R1(config-if)# clock rate<rate in bps>

the bandwidth can also be change according to the user requirements.

1R1(config-if)#bandwidth<kbps>

The encoding scheme used in serial interface us Non Return Zero(NRZ). The complete opposite work is done by Non Return Zero(NRZI). Communication is done from the both the sides. Encoding is changed .

1R1(config-if)# nrzi-encoding

The default condition is returned, by using command

1R1(config-if)# no nrzi-encoding

1.2.2 PARAMETERS IN DATA LINK LAYER:

Point-to-point, HDLC,SDLC,LAPB ,all these protocols are encapsulated across the line. Mostly used protocol is HDLC, which is supported by many vendors.

1R1(config-if)#encapsulation <protocol>

1.2.3. PARAMETERS IN NETWORK LAYER

A network address is no need to use in point-to-point connection as the data will have only in final destination network layer, Ip address can be assigned to a serial interface by using

1R1(config-if)# ip address<address> <mask>

1.3. FRAME ANALYSIS:

Ping command is used to find the status f the connection between the source and destination

1R1(config-if)#ping <destination ip address>

1.4 ASYNCHRONOUS LINES:

Data is transmitted intermittently . The best example for the asynchronous line is telephone as both the parties can talk each other . The system is connected to the router by means of modem. Data is transmitted one character at a time, where each character is 5 to 8 bits of length. EIA/TIA-232 cable is used for console and auxiliary ports.

To know the available asynchronous and their numbers

Show line command is used, where auxiliary port has 65 to 3620 routers.

1) we have to create an asynchronous interface

1R1(config-if)#interface async number

2)Data link protocol is used . The encapsulation command is used to select a data link protocol.

1R1(config-if)#encapsulation <protocol>

example: 1R1(config-if)#encapsulation <ppp>

3) We have to enable the dedicated mode ,which makes router for sending prompt to the user

1R1(config-if)#async mode dedicated

4) we have to assign the ip address

1R1(config-if)#ip address

2. IPv4 ADDRESSING

2.1 Introduction

Internet protocol plays an vital role in communication between the source and destination. Source transmits the data by considering the destination ip address. If the user wants to get the data ,user must know the ip address of the source.

They are two types of IP address they are

IPv4 and IPv6. IPv6 uses 128 bit format and IPv4 address consist of 32 bit, they are represented in dot decimal format, and consist of four decimal . It consist of five classes they are

Class A: 0-127 is the range 1 network id 3 host id

Class B: 128-191 is the range 2 network id 2 host id

Class c: 192-223 is the range 3 network id 1 host id

Class D and Class E are not used for limited way(future purpose or multitasking)

Figure: 2.1 Class diagram of IPv4(SOURCE:

(source: http://www.eventhelix.com/realtimemantra/networking/ip_routing.html

Private IP address:

Class A: 10.0.0.0 to 10.255.255.255

Class B: :172.16.0.0 to 172.31.255.255

Class C :192.168.0.0 to 192.168.255.255

private IP address are free

2.1.1 BINARY AND DOTTED DECIMAL REPRASENTATION:

The conversion between binary and decimal is done, by keeping the number 1 where the particular number in two power is used to get the result and gives the decimal number

2n.......22.21,20.

Figure 2.1.1.a : binary to decimal conversion

In the above diagram the decimal equivalent number is 101 .The addition of 101 is made by keeping the 1 as selected and 0 as no selected. The places above the 64 +32 +4 +1=101. This is equivalent to 01100101.

2.2 NETWORK CLASSES :

As mentioned above IPv4 contains 5 classes they are differentiated based on their ranges .Each class contains the priority bit, which is used to calculate the subnet mask.

Class A------ N.H.H.H (contains one network and three host )

8 Bits for network and 24 bits for host

Class B ------ N.N.H.H (contains two network and two host )

16 Bits for network and 16 bits for host

Class C------ N.N.N.H (contains three network and one host )

24 Bits for network and 8 bits for host

No of network : 2 n-p (P is the priority )

No of host: 2n-2 (We can't use first and last address as both will be for network ID and other for host ID )

N is the no of bits

priority bits for class A is 1(0)

priority bits for class B is 2(10)

priority bits for class C is 3(110)

Figure: Classes of A,B,C by considering priority bits.

class Network Host

A 126 1677214

B 16,384 65,384

C 20,97,152 254

Table 2.1.2 IP Host and Network ID of class A,B,C

The host and network id are calculated by using

No. of subnets = 2n

No. of Host=2n-2

.

2.3 SUBNET MASK :

By mask we can determine for which subnet the IP address. It mainly differentiate from one class to other. The default subnet mask for

classes are

Class A 255.0.0.0 ------------- N.H.H.H

Class B 255.255.0.0---------- N.N.H.H

Class C 255.255.255.0- -------N.N.N.H

Subnet mask performs bitwise AND operation with IP address and provides Network address. The default subnet for all classes is given by considering the network id and host id. In the places of network id 255 is placed and in the place of host 0 is placed.

2.3.1 SUBNETMASKING

The main task of subnet masking is to avoid the wastage of the IP address. As LAN cannot handle hundreds of host . The remaining IP address are lost, to avoid this problem subnet masking is done. The partition is done in smaller parts to use the address effectively. Network portion is extended ,the number of bits added to the network portion is considered as number of subnets

Broadcast address : Is the last address in the network

Net ID + all one's in the host part

Network address: After performing the "AND" operation between IP address and network address

Example

For the IP address 201.212.10.40/29

29 is the customised subnet mask

11001001 .11010100 .00001010 .00101000

11111111 . 11111111 .11111111 .11111000

­________________________________|network part

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­________________________________|___host part

__________________________________________

11001001 . 11010100 .00001010 . 00101000 - Network ID

__________________________________________

Subnet Mask : 11111111.11111111.1111111.11111000 ----- 255. 255. 255. 248

Network ID: 11001001.11010100.00001010.001010000 ------ 201.212. 10.40

Broadcast address – Host part is replaced by 1 at 0 place will get by adding

11001001.11010100.00001010.00101111 i.e. 201. 212.10.47

2.4 VARIABLE-LENGTH SUBNET MASKS (VLSM)

VLSM is used to divide the ip address to subnets of different sizes. Where as in subnetting the size of the subnet is are divided in same ratio. IP address are break down in subnets and they are placed according to the need of individual in network. It also called as classfull IP address because in the classfull IP address also follows the same rule and minimize the wastage of IP address.

Figure 2.4 Example of VLSM

Example: Ip address with 172.16.0.0/16 with serial links 30-bit length

Level 1 : (Clouds-1 serial links -4)

 

According to the diagram in level 1 it has one cloud and four serial connection, as each connection as two interfaces ,the problem is solved.

As each

cloud 172.16.0.0

Serial Links

A  172.16.0.4/30  B  172.16.0.8 /30     C   172.16.0.12 /30       D 172.16.0.16/30 

 

A is connected two interfaces 172.16.0.5  and 172.16.06

B is connected two interfaces 172.16.0.9  and 172.16.0.10

C is connected two interfaces 172.16.0.13 and 172.16.0.14

D is connected two interfaces 172.16.0.17 and 172.16.0.18

Level 2 (Clouds-4 serial links -10)

 

According to the diagram in level 1 it has one cloud and four serial connection, as each connection as two interfaces ,the problem is solved 

 

Cloud    172.16.10.0/24

     

   Serial Links

A 172.16.10.4 /30   B 172.16.10.8/30

 

A is connected two interfaces 172.16.10.5  and 172.16.10.6

 B is connected two interfaces 172.16.10.9  and 172.10.10.10

 

 

Cloud 172.16.11.0/24

     

   Serial Links

A 172.16.11.4/30     B 172.16.11.8/30

 

A is connected two interfaces 172.16.11.5  and 172.16.11.6

 B is connected two interfaces 172.16.11.9  and 172.16.11.10

 

 

 

    cloud 172.16.12.0/24

     

   Serial Links

A 172.16.12.4/30   B 172.16.12.8/30 C 172.16.12.12/30

 

A is connected two interfaces 172.16.12.5 and 172.16.12.6

 B is connected two interfaces 172.16.12.9  and 172.16.12.10

C is connected two interfaces 172.16.12.13  and 172.16.12.14

  cloud   172.16.13.0/24

     

   Serial Links

A 172.16.13.4/30   B 172.16.13.8/30 C 172.16.13.12/30

 

A is connected two interfaces 172.16.13.5 and 172.16.13.6

 B is connected two interfaces 172.16.13.9  and 172.16.13.10

C is connected two interfaces 172.16.13.13  and 172.16.13.14

2.5 CONCLUSION

IP address plays an important role for communication between two devices. As the demand of using internet became more ,which leads to more IP address this is the purpose IPv6 . IPv6 uses 128 bit address . To overcome the wastage of IP address in IPv4 subnet mask and variable subnet mask came in to existence. The place from where the broadcast is done is called as LAN.

3. VLANS/ETHERNET NETWORKS

Introduction: Different users are connected to each other by repeaters or hub. By using this devices data collision can be decreased. As these device doesn't allow the collision in the network, the data rate will be very high ,and it also allows broadcast the data for the destination user who are connected in the network. As VLAN'S can provide domains, therefore the cost is decreased because the usage of routers is not there.

Figure 3.1 A Typical VLAN

3.1.1VLAN CONFIGURATION:

To check the existed VLAN's on switch

show VLAN brief

If any VLAN'S are presented then remove all previous VLANS

no VLAN vlan-number

3.2 SWITCH CONFIGURATION :

Switch plays an important role in VLAN , because it as interface between the router and and user device. There are some commands which should be performed

Switch(Config)#Interface GigabitEthernet <interface number>

The connect can also be in the form of FastbitEthernet.

Switch(Config)#switchport mode access

Switch(Config)# Switchport access vlan <vlan-id>

For verification of status of the switch use

show vlan brief

fig 3.2SWTICH CONFIGURATION(SOURCE LAB SESSION)

3.3 ROUTER CONFIGURATION:

To start the communication ,we need to assign the IP address to the mutual interface that are connected to each other.

1R1(Config)#interface GigabitEthernet <interface number>

1R1(Config-if)#ip address<address><mask>

mask will be the depend on the IP address

1R1(Config)#no shutdown

ping command be used to verify the connection between the routers ,and we can also see the outgoing and incoming packets flow of the routers by using debug command.

1R1# debug ip packet[detail]

To check the connectivity status through out the programme

1R1#show ip interface brief

FIG 3.3 (SOURCE: Router configuration in lab

4. ROUTING INFORMATION PROTOCOL

4.1 INTRODUCTION:

Routing Information Protocol is distance vector protocol. It is a open standard protocol, uses bellman -Ford algorithm, with classfull routing protocol and updates are periodically updated using 255.255.255.255 . Routing table is updated

Metric is Hop count

Maximum Hop count is 15

If Hop count is 16 the network is unreachable

Load balancing is done the RIP. That is, packets are divided and send in a different paths

Administrative distance:

It is a mechanism giving a rank to the routing protocols. Based on this distance router will select which is the best routing protocol. Range is 0-255.

4.2 STATIC AND DYNAMIC ROUTING

Routes for each destination network has to be manually configured by the administer. Requires destination network ID for configuration and used in small networks. Administrative distance for static route is 1.Administraive distance is the reliability of the routing protocol and range is 0-255,lesser then the administrative distance, higher priority

SYNTAX:

1R1(config)#iproute <destination network Id> <next hope address>

Topology changes can't be dynamically updated, and compulsory need of all destination network ID's and mainly used in small organization

Dynamic routing displays changes in the network topology are updated dynamically ,only the directly connected networks information is required for configuration. It is used in large and medium networks. More bandwidth is used for sending the updates

4.3 Difference between RIP V1 and RIP V2

RIP V1

Classful routing protocol and it does not advertise subnet mask information in routing update .It works with broadcasting -255.255.255.255,it doesn't not provide authentication.

RIPV2

Classless routing protocol and it does not advertise subnet mask in routing update .It works with broadcasting -224.0.0.9 it doesn't not provide authentication.

Configuration RIPv2

1R1(Config)##router rip

1R1(Config-router)#version 2

4.4Configuration of RIP

Enable RIP

router(config)#ip routing

connected to router

router(config)#router rip

router(config-router)#network <Network ID>

4.5 Conclusion:

Routing Information Protocol is distance vector protocol. which uses open standard protocol, with bellman -Ford algorithm,.Classful routing protocol and updates are periodically updated using 255.255.255.255 . Routing table is updated . The ultimate goal is to send data in easier way, by reducing the traffic in the channel.