Set # 01

Delivered By: Engr Tahir Niazi

INTERNET ARCHITECTURE &

PROTOCOLS

What is Internet?

Basically it is called Network of networks

Nuts and Bolts (Pieces of internet)

Services description (applications)

What is Protocol? (agreement)

Nuts & Bolts

Internet composed of million of devices attached

Hosts or end systems

Communication links

Routers and switches

Transmission rate

Packets/datagram

Route and path

Internet service provider

Nuts & Bolts

Services Description:

Multiple end systems that exchange data with each other called

distributed application

Electronic mail

Web surfing

Social networks

Instant messaging

VoIP

Video streaming

Gaming

file sharing

Protocols:

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 or other event.

Human analogy concept

Networks analogy concept

Humans & Computer Network Protocol:

The Network Edge:

End systems or Hosts that are connected to internet are located at

the edge of the network

Access Networks:

The Network that physically connects an end systems to first

router (also known as edge router)

Home Access: DSL,Cable, FTTH DSL and Cable normally deployed for residential broadband access

Ethernet & Wi-Fi Access:

Communication media:

Twisted pair

Coaxial cable

Optical fibre

Terrestrial radio channels

Satellite radio channel

The Core Network:

Switching (Circuit & packet) take place

long messages into smaller chunks of data known as packets.

packet travels through communication links and packet

switches.

Packets are transmitted over each communication link at a rate

equal to the full transmission rate of the link. So, if a source end

system or a packet switch is sending a packet of L bits over a link

with transmission rate R bits/sec, then the time to transmit the

packet is L/R seconds.

Core Network:

Packet Switching: Store and forward

means that the packet switch must receive the entire packet

before it can begin to transmit the first bit of the packet onto the

outbound link

Queuing delays and Packet loss:

arriving packet needs to be transmitted onto a link but finds the

link busy with the transmission of another packet, the arriving

packet must wait in the output buffer this is known as Queuing

delay

amount of buffer space is finite, an arriving packet may find that

the buffer is completely full with other packets waiting for

transmission. In this case, packet loss will occur

Forwarding table & Routing protocols:

When a packet arrives at a router, the router examines the

address and searches its forwarding table, using this destination

address, to find the appropriate outbound link

routing protocol may, for example, determine the shortest path

from each router to each destination and use the shortest path

results to configure the forwarding tables in the routers

Packet Switching:

Store & forward

Delays & packet loss

Forwarding table

Circuit switching:

Circuits (dedicated end to end)

Resources reserved (FDM,TDM)

Traditional telephone networks

Circuit Vs Packet switching:

Circuit switching: carry bit streams

a. establishes a dedicated circuit

b. links reserved for use by communication channel

c. send/receive bit stream at constant rate

d. example: original telephone network

• Packet switching: store-and-forward messages a. No dedicated circuit is

established

b. utilizes resources according to traffic demand

c. send/receive messages at variable rate

d. example: Internet

Telecom/Computer networks

Circuit-switched networks

FDM TDM

Packet-switched networks

Networks with VCs

Datagram Networks

Network Taxonomy:

Internet Architecture:

Tier 1, Tier 2, Tier 3 ISPs

End system to the internet through access ISP

Access ISP can provide guided or un guided connection

Provider & Customers

CPE, PoP, IXP, Content providers

Interconnection of ISPs

Delays in packet switched networks:

The most important of these delays are the nodal processing

delay, queuing delay, transmission delay, and

propagation delay

Nodal Processing:

- time required to examine the packet’s header

- determine where to direct the packet

- check for bit-level error

- typically on the order of microseconds or less

Delays in packet switched networks:

Queuing delay:

- Time taken at queue

- Heavy traffic more delay, less traffic low delay

- Microsecond to millisecond

Transmission delay:

- Time required to send all of the packet’s bits onto the link

- Transmission Delay = L/R ,Where L is the length of the packet

and R is the bandwidth of the link

- Microsecond to millisecond

Delays in packet switched networks: Propagation delay:

- Once a bit is pushed into the link, it needs to propagate onto the link.

The time required to propagate from the beginning of the link to the

end

- Depend on physical medium used

Protocols Layered Architecture:

Why layered architecture?

Take human analogy

Internet & OSI Model:

Operation: Internet Model

Encapsulation (headers & control info)

Message- Segment-Packets-Frames-Bits

Multilevel addressing

Layered Hierarchy: Example

An IP address is a

32-bit

address.

What is an IP Address?

The IP addresses

are

unique.

Address space rule

addr15 addr1

addr2

addr41 addr31

addr226

………….. …………..

………….. …………..

…………..

………….. …………..

The address space in a protocol

That uses N-bits to define an

Address is:

2N

The address space of IPv4 is

232

or

4,294,967,296.

01110101 10010101 00011101 11101010

Binary Notation

Dotted-decimal notation

0111 0101 1001 0101 0001 1101 1110 1010

Hexadecimal Notation

75 95 1D EA

Example 1

Change the following IP address from binary

notation to dotted-decimal notation.

10000001 00001011 00001011 11101111

Solution

129.11.11.239

Example 2

Change the following IP address from

dotted-decimal notation to binary

notation:

111.56.45.78

Solution

01101111 00111000 00101101 01001110

Example 3

Solution

Find the error in the following IP Address

111.56.045.78

There are no leading zeroes in

Dotted-decimal notation (045)

Example 3 (continued)

Solution

Find the error in the following IP Address

75.45.301.14

In decimal notation each number <= 255

301 is out of the range

Example 4

Solution

Change the following binary IP address

Hexadecimal notation

10000001 00001011 00001011 11101111

810B0BEF16

CLASSFUL

ADDRESSING

In classful addressing the address space is

divided into 5 classes:

A, B, C, D, and E.

Finding the class in binary notation

Finding the address class

Example 6

Solution

Find the class of the following IP addresses

00000001 00001011 00001011 11101111

11000001 00001011 00001011 11101111

•00000001 00001011 00001011 11101111

1st is 0, hence it is Class A

•11000001 00001011 00001011 11101111 1st and 2nd bits are 1, and 3rd bit is 0 hence, Class C

Finding the class in decimal notation

Example 7

Solution

Find the class of the following addresses

158.223.1.108

227.13.14.88

•158.223.1.108

1st byte = 158 (128<158<191) class B

•227.13.14.88

1st byte = 227 (224<227<239) class D

Netid and hostid

Network Addresses

The network address is the first address.

The network address defines the network to the

rest of the Internet.

Given the network address, we can find the

class of the address, the block, and the range of

the addresses in the block

Example 8

Solution

Given the network address 132.21.0.0, find the

class, the block, and the range of the addresses

The 1st byte is between 128 and 191.

Hence, Class B

The block has a netid of 132.21.

The addresses range from

132.21.0.0 to 132.21.255.255.

Mask

• A mask is a 32-bit binary number.

• The mask is ANDeD with IP address to get

• The block address (Network address)

• Mask And IP address = Block Address

Masking concept

AND operation

The network address is the

beginning address of each block.

It can be found by applying

the default mask to

any of the addresses in the block

(including itself).

It retains the netid of the block

and sets the hostid to zero.

Default Mask

Class A default mask is 255.0.0.0 /8

Class B default mask is 255.255.0.0 /16

Class C Default mask 255.255.255.0 /24

Find Network ID & Broadcast Address Broadcast Address: An IP Address that allows information to

be sent to all machines on a given subnet rather than a specific

machine

Example:

192.168.1.15/24

Exercise:

Find the Network and Broadcast Addresses for

each of the following

1. 10.10.1.97/23

2. 192.168.0.3/25

3. 172.16.5.34/26

4. 192.168.11.17/28

Exercise Answers:

1. The network Address is 10.10.0.0 and the

Broadcast Address is 10.10.1.255

2. The network Address is 192.168.0.0 and the

Broadcast Address is 192.168.0.127

3. The network Address is 172.16.5.0 and the

Broadcast Address is 172.16.5.63

4. The network Address is 192.168.11.16 and the

Broadcast Address is 192.168.11.31

Internetworking Devices: Hub/Repeater

Bridge

Switches

Router

Hub/Repeater:

Repeat the signal with greater power

1 collision domain

1 broadcast domain

Layer 1

Internetworking Devices:

Bridge:

Main function (learning, forwarding, filtering)

2 collision domain

1 broadcast domain

Layer 2

Switch:

Each port separate collision domain

1 broadcast domain

Full duplex

Layer 2

Internetworking Devices:

Router:

Works on IP address

No broadcast domain

Routing

Layer 3

DHCP

Dynamic Host Configuration Protocol

Allow IP Address / Netmask / Gateway Information to be

allocated dynamically

- At random, OR

- Predetermine for specific MAC address

Typically given for a period of time

DHCP server can be server based or router based

DHCP Process: Four steps

- DHCP discover (broadcast)

- DHCP offer (unicast)

- DHCP request (broadcast/unicast)

- DHCP Ack (unicast)

DHCP on window server:

ARP: Address Resolution Protocol

Interaction between IP and MAC

Host 138.37.35.215 want to send a packet to 138.37.35.74

IP packet needs to be put in an Ethernet frame with MAC

address

Need to find MAC address for 138.37.35.74

ARP sends broadcast asking for the MAC address

Usually the destination host will reply with it’s own MAC

address

Cached in arp table

ARP: different Subnet

Host 138.37.35.215 wants to send a packet to 138.37.32.214

(different subnet)

IP packet needs to be put in an Ethernet frame with MAC

address as before

Different subnet so will need to go through a router

Routing table (see later) provides address of router

- (138.37.35.254 here)

arp will find the MAC address of the router

ARP Process:

Two Address concept:

DNS:

Domain name system

Applications refer to hosts etc by name

Need to map these to IP addresses

Reverse look up

Originally a file, hosts.txt, that listed all the hosts and their IP

addresses - flat structure; every night all the hosts would collect

this file from the host that maintained it - not scalable

DNS ( Domain Name System) distributed database now used

Domain Name System:

DNS is a hierarchical, domain-based naming scheme and a

distributed database system for implementing this naming

scheme using Delegation of Authority concept

Hierarchically structured distributed database

Each element of the hierarchy is referred to as a domain

Mainly used for mapping host names and email destinations to IP

addresses

Domain Name System:

At the top of the hierarchy is the root domain, known as “.”

Sub domains directly underneath the root domain are called top

level domains

Domains directly underneath top-level domains are called

second-level domains, and so on

Any domain in the name space can be referred to by the domain

names in its hierarchical path separated by dots – e.g.

Example:

abcdefg@uos.edu.pk

Host name, domain name, fully qualified domain name

Consider another example:

Nameservers:

Information on the root domain resides on a select number of

root nameservers around the Internet

The root nameservers hold data for all the top-level domains

Top-level domains

- two-letter abbreviations for each country, such as uk and us

- special domains such as edu, com, net, gov etc

These root nameservers make it possible for every host on the

Internet to have access to the complete DNS database

DNS Principle:

Each domain has one or more Resource Records (RRs)

Computers query the nameservers to find out information about

domains in the DNS

Each nameserver handles a specific part of the DNS referred to

as a zone. A zone is a collection of domains

Since no single server in the Internet knows the addresses of all

other hosts, the responsibility of resolving addresses to IP

mapping is then delegated to the authority servers of that zone

DNS Resolver:

Clients use resolvers

- resolvers are the nameservers’ clients

The resolver's function is to resolve queries from the user’s

terminal. To do that, it queries a nameserver, which then returns

either the requested information or a referral to another server

This can be done in two ways:

- Recursively

- iteratively

Recursive Query: The resolver asks the DNS server within its own domain for the

IP address of the named destination.

If this is not known, the query is escalated to the next higher

nameserver, responsible for a higher domain.

This may escalate the query higher etc.

Iterative Query:

SUMMARY:

What is Internet?

Different parts of Network

Network Taxonomy

Delay, types of delay and Packet loss

Layered & Internet Architecture

IP addressing

Network and Broadcast address

Internetworking devices

DHCP, ARP & DNS

Q & A

IAP, University of Sargodha, CS & IT Dept