networking and its fundamentals [coral telecom]

Networking and its

fundamentals

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Outline

• What is network?

• Basic requirements of a network

• Components of a network

• Protocols

• Classification of computer networks

• TCP/IP protocol stack

• Applications

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What is a network?

• A computer network is "A set of data

processing nodes that are interconnected

for the purpose of data communication".

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Basic requirements

for a network

• In order for a network to function, it must meet three basic requirements:

– It must provide connections• Connection refers to the hardware.

– It must provide communications• Communication is the way in which the devices

talk to each other.

– It must provide services• Services are the things which are shared with the

rest of the network.

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Components of network

• Message

• Sender

• Receiver

• Protocol

• Medium

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Protocols

• Set of rules governing data

communication.

• Integration of three basic functions:

– What is communicated?

– How is it communicated?

– When is it communicated?

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Classification of

computer networks

• On the basis of scale or extent of reach of

network

– LAN, MAN, WAN

• On the basis of connection method

– hardware technology: Wired, Wireless, Hybrid

• On the basis of functional relationship

– Client-Server,

– Peer-to-peer

• On the basis of network topology

– Physical layout: Mesh, Star, Bus, Ring, Hybrid

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Local Area Network

• In general privately owned, which covers a small

area

• Network in a building

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Metropolitan Area Network

• Extends over an entire city

• It may be a single network or a means of

connecting a number of LANs together.

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Metropolitan Area Network

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Wide area network

• Generally covers a country, a continent and can

be extended to the whole world

• Example: Internet

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Mesh network

• Point to point dedicated link between any

two nodes

• Elimination of traffic problem

• Provides security and privacy of data

• Robust

• Not Scalable

– Interface problem

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Mesh network

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Star network

• Each node is connected to the central

controller.

• It does not allow direct traffic between

devices.

• Robust, provided the controller remains

active

• Scalable

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Star network

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Bus network

• One long cable act as a backbone to link

all the devices in a network.

• Nodes are connected to bus cable by the

drop lines and taps.

• No security and privacy to data.

• Broadcasting of data

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Bus network

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Ring network

• Each device has a dedicated point to point

connection only to the two devices on

either side of it.

• No broadcasting of data.

• Scalable

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Ring network

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TCP/IP Protocol Stack

Fig.: TCP/IP Stack

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Physical Layer

• Task

– Transmit raw bits over communication channel

• Fundamental unit of transfer: Bit

• Examples

– Twisted pair

– Coaxial cable

– Optical fiber cable

– Radio transmission

– Microwave transmission

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Physical Layer –

Example

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Fig.: Physical Layer Example

Data Link Layer

• Task

– Provide raw transmission across a link

– Error detection and correction

– Flow control

• Fundamental unit of transfer: Frame

• Example

– Protocols such as HDLC and PPP

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Data Link Layer -

Example

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Fig.: Data Link Layer Example

Network Layer

• Task

– Host to host delivery

– Routing

– Congestion control

• Fundamental unit of transfer: Packet

• Example

– IP

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Network Layer –

Example

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Fig.: Network Layer Packet Transfer

Internet Protocol - IP

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Fig.: IP Addressing

IP Example

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Fig.: IP Addressing Example

Transport Layer

• Task

– Process to process message delivery

• Fundamental unit of transfer: TPDU

• Examples

– TCP (Transmission Control Protocol)

– UDP (User Datagram Protocol)

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Transport Layer -

Example

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Fig.: Transport Layer Functioning

Application Layer

• Task

– Provides services to users

• Fundamental unit of transfer: Message

• Examples

– WWW

– Email

– Chat

– Multimedia streaming

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Layering – Physical Communication

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applicationtransportnetwork

linkphysical

applicationtransportnetwork

linkphysical

applicationtransportnetwork

linkphysical

applicationtransportnetwork

linkphysical

networklink

physical

data

data

Domain Name System -

DNS

• Task

– To resolve host name

• Internet name space

– Over 200 domains: Generic and Countries

– Sub domains

– Hosts

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Accessing Website

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Fig.: Path for www.iitb.ac.in

Accessing Website

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Fig.: Looking up www.iitb.ac.in

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Networking Devices

• HUB

• Bridge

• Switch

• Router

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Switching is done on the basis of the source and destination Ethernet addresses

Switching is done, based on the IP address

of the endpoints

Questions

• What is difference between IP address and Ethernet Address?

• What is a Public and Private IP?

• How is data sent over internet?

• How are IP addresses allocated to my PC?

• What is difference between switch and router?

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Questions

• What is a layer 2 switch?

• Where and why do we use NAT?

• What is the significance of subnet mask?

• What is the difference between broadcast

and Multicast?

• What is streaming?

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IP Addresses

• 32 bits in existing IP (IPv4), 128 bits in IPv6 (future).

• Typically written in form xxx.xxx.xxx.xxx (e.g. 192.168.0.1)

• Binary Representation:

• Logical Identification of a system in a

network

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11000000 10101000 00000000 00000001

IP Addresses

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• Hierarchical Division in IP Address:

Network Part (Prefix)

describes which physical network

Host Part (Host Address)

describes which host on that network

Network Host

192 168 0 1

11000000 10101000 00000000 00000001

• Define which bits are used to describe the Network Part and which for hosts

• Different Representations:– decimal dot notation: 255.255.255.0

– binary: 11111111 11111111 11111111 00000000

– hexadecimal: 0xFFFFFF00

– number of network bits: /24

Subnet Mask

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• For E.g.

• All 0’s in host part: Represents Network– e.g. 192.168.0.0/24

• All 1’s in host part: Broadcast– e.g. 192.168.0.255 (192.168.0.0/24)

• 127.0.0.0/8: Loopback address (127.0.0.1)

Subnet Mask

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IP 192 168 0 1

IP

(Binary)

11000000 10101000 00000000 00000001

Netmask 255 255 255 0

(Binary) 11111111 11111111 11111111 00000000

Network Host

• The Subnet mask is used to define size of a network

• E.g. a subnet mask of 255.255.255.0 or /24 implies 32-24=8 host bits– 2^8 minus 2 = 254 possible hosts

• Similarly a subnet mask of 255.255.255.224 or /27 implies 32-27=5 hosts bits– 2^5 minus 2 = 30 possible hosts

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Allocating IP Addresses

Public / Private

IP Addresses• Public IP

• Private IP

• Public IP allotted by a world body – unique all around the

world

• Unlike public IP, private IP addresses are not valid on

the Internet.

• Range of Private IP addresses:

– 10.0.0.0 to 10.255.255.255

– 172.16.0.0 to 172.31.255.255

– 192.168.0.0 to 192.168.255.255

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MAC Address

• MAC Address – Media Access Control Address – A hardware address that uniquely identifies each node of a network

• 48 – bit address

• MAC Address are also called as Ethernet

Address

• MAC address are unique and they are allotted

by the manufacturer of the Ethernet device

• MAC address cannot be modified by the user

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Router

• A specialized device (computer) connected to

more than one to transfer data packets from one

network to another.

• IP networks are packet-switched networks,

which means that the packets can take different

routes between a source and a destination host.

• The whole Internet consists of a number of

networks connected to each other via routers.

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Functions of Router

• Routers operate at the Network Layer

(OSI layer 3)

• Layer 3: Network layer (e.g. IP)

– Unreliable

• if packet gets lost, network layer doesn’t care

• higher layers can resend lost packets

– Forwards packets hop by hop

• receive from one link, forward to another link

• There can be many hops from source to

destination

• Packet-switched networks, packets can take

different routes between a source and a

destination host.

OSI Model Layers

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

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• Layer 3: Network layer (e.g. IP)

– Makes routing decisions

• how can the packet be sent closer to its

destination?

• routers can talk to each other to exchange

information about network topology

• The addresses used by the IP protocol are 32-bit

numbers.

• IP addresses are split up into four 8-bit numbers

called octets. For example, 193.12.15.1.

OSI Model Layers

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

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Functions of Router

Router (Example)

• The first networks is identified by

the IP-number 193.12.15.0 and

the other network is identified by

the IP-number 10.5.17.0.

• On every network there are two

hosts. Observe that the first three

octets in the IP-numbers are the

same as in the IP-number of the

networks.

• The router that connects the two

networks has two interfaces with

IP-numbers that belong to each

respective network.

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Routing Decision

• The router algorithm includes four different

steps.

– The first question is if the destination host is

on a network that is directly connected to the

router. If the answer to this question is yes the

router makes a direct delivery to the

destination host.

– Otherwise the next question is if the

destination host is to be found in the routing

table. If the answer is yes, then the router

sends the packets to a router that is closer to

the destination host.

– Otherwise the router looks to see if the

network, to which the destination host is

connected, is to be found in the routing table.

If the answer is yes, then the router sends the

packets to a router that is closer to the

destination host.

– The last chance for the router is to use a

default router to send the packet to. Now it is

up to the default router to find the destination

host. The default router is sometimes also

called the default gateway.

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Routing Table

• How does the router choose where to send

the packets?

• The router keeps the routing information in a

table. This information tells the router how to

reach remote networks and hosts. A catch-

all entry, also called the default router must

generally be supplied. All packets to an

unknown network or host are sent to the

default router.

• In the picture you see a router with its

specific routing table. If the packets are to

be delivered to the host with IP-number

192.1.5.10, the router sees that the

destination host belongs to the network

192.1.5.0. The routing table says that this

network can be reached via the router

192.1.8.2.

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Administrative Distances

• The administrative distance (AD) is used to rate

the trustworthiness of routing information

received on a router from a neighbor router.

• An administrative distance is an integer from 0 to

255, where 0 is the most trusted and 255 means

no traffic will be passed via this route.

• Lowest AD will be placed in the routing table

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Static Routing

• Static routing is the term used to refer to the manual

method used to set up routing.

• Static Route has default administrative distance of 1

• Advantages:

– Easy to predict and understand in small networks

– Simple to setup

• Disadvantages:

– An administrator enters routes into the router using configuration

commands.

– Requires extensive planning and has a high management

overhead

– When there is a change in the network or a failure occurs

between two statically defined nodes, traffic will not be rerouted.

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Dynamic Routing

(Routing Protocols)• Routing protocols are used so that the routers in a

network can learn things from other routers

automatically.

• Routing protocols are used when we have many different

routers

– if one link goes down, the routing protocol can teach other

routers in the network a new way to the destination.

• No need for routing protocols in Point-to-Point network

with no alternative routes.

– Routing protocols just give you a lot of ”overhead” traffic in your

network.

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Routing Protocols

• Two groups of routing protocols:– Interior Gateway Protocol, IGP which is used

inside a local network. This network is also called an

autonomous system or AS.

– Exterior Gateway Protocols, EGP, and is used

between autonomous systems. EGP, is normally

used by the Internet service providers.

• Three examples of IGP protocols

are:– RIP, which stands for Routing Information

Protocol.

– IGRP, which stands for Interior Gateway Routing

Protocol and EIGRP, which stands for Enhanced

Interior Gateway Routing Protocol and they are

two Cisco specific protocols.

– OSPF, which stands for Open Shortest Path

First.

• Two examples of EGP routing

protocols are:– BGP, which stands for Border Gateway Protocol.

– GGP, which stands for Gateway to Gateway

protocol. This protocol is history and is not used

today.

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RIP

(Routing Information Protocol)• Distance vector routing protocol, The distance-vector

protocols find the best path to a remote network by

judging distance.

• RIP is stable, widely supported, and easy to configure

• RIP uses hop count metric to measure distance, it only

takes into consideration the number of routers you need

to pass in order to reach the destination host. This is

called the cost to reach the destination host.

• RIP does not take into account the quality or bandwidths

of the connected links.

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RIP

(Routing Information Protocol)• RIP broadcasts its routing table every 30 seconds in

order to share with other routers. This gives a lot of

overhead traffic on the network.

• The maximum number of hops in a path is 15.

• If increasing the metric value by 1 causes the metric to

be infinity (that is, 16), the network destination is

considered unreachable.

• RIP has default Administrative Distance value of 120

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RIP V 1/2

• RIP version 1 uses only classful routing, which means

that all devices in the network must use the same subnet

mask.

• RIP version 1 doesn’t send updates with subnet mask

information in tow.

• RIP version 2 provides something called prefix routing,

and does send subnet mask information with the route

updates. This is called classless routing.

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RIP

(Example)• This picture shows three routers using

RIP. The router B, for example was

originally configured with the

information about the directly

connected networks. The rest of the

information in the routing table has

been learned from the other routers in

the network.

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OSPF-Open Shortest Path First

• Based on Dijkstra’s algorithm, first, a shortest path tree is constructed, and then the routing table is populated with the resulting best paths.

• Link-state protocol, also called shortest-path-first protocols

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OSPF-Open Shortest Path First

• Uses link state routing strategy– Each router keeps list of state of local links to

network.

– Transmits update state information to all other routers within the same area.

• Route computed on least cost based on user cost metric.

OSPF-Network Hierarchy

• OSPF is supposed to be designed in a hierarchical fashion, which

basically means that you can separate the larger internetwork (AS)

into smaller internetworks called areas.

• OSPF must have an area 0 called Backbone Area, and all routers

should connect to this area if at all possible

• Routers that connect other areas to the backbone within an AS are

called Area Border Routers (ABRs).

• An area’s topology is invisible to entities outside the area.

• OSPF backbone is responsible for inter area communication. It consists of all Area Border Routers, networks not wholly contained

in any area, and their attached routers.• An ASBR is a router that is connected to more than one AS and that

exchanges routing information with routers in other ASs. ASBRs typically also run a non-IGP routing protocol (e.g., BGP), or use static routes, or both. An ASBR is used to distribute routes received from other ASs throughout its own AS.

OSPF Design Example

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OSPF-Features

• OSPF provides the following features:– Consists of areas and autonomous systems

– Minimizes routing update traffic

– Allows scalability

– Supports VLSM/CIDR

– Has unlimited hop count

– Allows multi-vendor deployment (open standard)

Redundancy

• Redundancy means having more

than one possible path to reach

the destination host.

• In the picture you can see that

there are two alternative ways

between the host A and host B

which gives us redundancy. On

the Internet for example, there are

many alternative ways to reach a

host or a network, which means

that Internet has a lot of

redundancy.

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Dynamic Update

• To use all the benefits of a secure and

redundant network structure a routing

protocol is needed. The routing

protocol must be used so that the

routers can exchange information

continuously about the status of the

links between the different routers.

This means that the router information

is dynamically updated.

• In the picture you can see that a path

between routers has been broken.

With the help of routing protocols the

information about the broken link is

sent to other routers in the network.

This means that the routers will send

the packets using an alternative path.

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Some Terminologies

• DHCP - Dynamic Host Control Protocol– DHCP automatically configures the PC's IP address, the

gateway address and also the DNS address

• DNS - Domain Name Service – used to map domain names (e.g. www.coraltele.com) to IP

address and vice-versa

• NAT – Network Address Translation– networking protocol that allows network of private IP address to

be set up using a single Public IP address

• Gateway– a network point that acts as an entrance to another network

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Some Terminologies

• Broadcast– Packets are transmitted to all user terminals in a network

• Multicast– Packets transmitted to selected multiple recipients who have

joined the appropriate multicast group.

• Unicast– Packets transmitted to a single user.

• Streaming– Playing video or sound in real time as it is downloaded over the

Internet

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Some Terminologies

• PPP – Point-to-Point Protocol– Protocol encapsulating a connection to a TCP/IP network

through a modem and a telephone line

• PPPoE – PPP over Ethernet– The transport of PPP frames over Ethernet

• ATM – Asynchronous Transfer Mode– A high bandwidth, High speed, controlled-delay fixed-size packet

switching and transmission system integrating multiple data types (voice, video, and data).

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Thank You!

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