Networking and Its Fundamentals [Coral Telecom]
Transcript of 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
– 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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