Communication and Networks Assignment
Tubekbay001
0_Lesson19InternetAddressing.pptxCommunications and Networks
version 1.0
Diploma in Information Technology
Copyright © 2020 by Singapore Institute of Management Pte Ltd. All rights reserved.
Lesson 19: Internet Addressing
1
Lesson 19 Learning Outcomes
Describe the addressing scheme used on the Internet
Explain the IP address hierarchy
Explain the motivation behind CIDR
Distinguish between IPv4 and IPv6 addressing
2
Lesson 19 Outline
IPv4 Addressing
Classless Addressing
Berkeley Address
IPv6 Addressing
3
Seamless Communication
To achieve seamless communication system
Protocols must hide the details of physical networks and offer the illusion of a single, large network
The Internet is created entirely by protocol software
Addresses, packet formats, and delivery techniques independent of underlying hardware
4
Internet Addressing
Addressing is a critical component of the Internet
All host must use uniform addressing scheme
MAC addresses does not suffice as each network technology on the Internet defines its own
Internet Protocol (IP) address: supplied by protocols
Application programs can communicate without knowing the underlying hardware
Many protocols use IP addresses
5
IP Addressing Scheme
IP address (or Internet address) is a unique 32-bit number
Sender’s protocol must specify source IP address (itself) and destination IP address (receiver)
Network number (prefix) assignments must be coordinated globally
Suffixes are assigned locally without global coordination
6
Prefix and Suffix
Prefix: physical network of the host
Each network is assigned a unique prefix
Suffix: specific host/node on the network
Each host/node is assigned a unique suffix
Source: Douglas, C (2016) Computer Networks and Internets
7
Classful IP Addressing
Difficult choice to allocate bits for prefix and suffix
Large prefix: many networks, limited size each
Large suffix: many computers, limited networks
Original classful IP addressing divided IP address space into three primary classes
Each class has a different size prefix and suffix
Leading bits are used to identify class
8
IP Address Authority
ICANN handle address assignment and disputes but authorise registrars to assign prefixes
Registrars make blocks of addresses available to ISPs
ISPs provide addresses to subscribers
To obtain a prefix, a corporation usually contacts an ISP
9
Dotted Decimal Notation
Dotted Decimal Notation express each 8-bit section of a 32-bit number as a decimal value
Use periods to separate the sections
Treats each byte as an unsigned binary integer
0.0.0.0 to 255.255.255.255
Source: Douglas, C (2016) Computer Networks and Internets
10
Classful Addressing Limitations
Classful address are divided into unequal sizes to accommodate variety of scenarios
Class A is limited to 128 networks meant for ISP
Class C allows few hosts on a LAN
Source: Douglas, C (2016) Computer Networks and Internets
11
Meeting Growing Needs
Many demanded class A or class B address for future growth but many addresses were unused
Many class C addresses remained, but few wanted to use them
Can use variable prefix and suffix length:
Subnet addressing
Classless addressing
12
Subnet and Classless Addressing
Subnet addressing was originally used within large organizations
Classless addressing extended subnet addressing to all Internet
If a customer requests a prefix for a network that contains 55 hosts, a class C will be wasteful
Classless addressing allows the ISP to assign:
Prefix that is 26 bits long
Suffix that is 6 bits long
13
Classless Addressing
With classless addressing the prefix can be divided into several prefixes and assign each to a subscriber
Instead of wasting addresses, ISP can assign each of the four classless prefixes to a subscriber
Classful Class C
Classless
Source: Douglas, C (2016) Computer Networks and Internets
14
Address Masks
Classless and subnet require hosts and routers to store additional piece of information:
Boundary of prefix and suffix
To mark the boundary, IP uses a 32-bit value known as address mask or subnet mask
Hosts and routers compare prefix portion of the address to a value in their forwarding tables
bit-mask makes comparison efficient
15
Address Masks Comparison
Suppose a destination address (D), prefix (N) and address mask (M)
To test whether destination lies on specified network, router tests condition: N == (D & M)
Router uses mask with a “logical and (&)” operation to set the host bits of address D to zero (0)
Compares the result with the network prefix N
16
Address Masks Example
Consider the 32-bit prefix:
10000000 00001010 00000000 00000000= 128.10.0.0
32-bit mask:
11111111 11111111 00000000 00000000= 255.255.0.0
32-bit destination address:
10000000 00001010 00000010 00000011= 128.10.2.3
”AND” operation for destination address and address mask to extracts high-order 16-bits
10000000 00001010 00000000 00000000= 128.10.0.0
17
Practice 19.1
Why is there a need for classless addressing?
18
Lesson 19 Outline
IPv4 Addressing
Classless Addressing
Berkeley Address
IPv6 Addressing
19
Classless Inter-domain Routing
Source: https://www.youtube.com/watch?v=rJXvFWY4Ak0
20
Classless Inter-Domain Routing
Classless Inter-Domain Routing (CIDR) specifies addressing and forwarding
General form of CIDR: ddd.ddd.ddd.ddd/m
ddd: decimal value for an octet of the address
m: number of one bits in the mask
192.5.48.69/26 specifies a mask of 26 bits
21
CIDR Example
Assume an ISP has 128.211.0.0/16
customer1 CIDR: 128.211.0.16/28
customer2 CIDR: 128.211.0.32/28
The binary value customer1 is:
10000000 11010011 00000000 0001 0000
The binary value assigned to customer2 is:
10000000 11010011 00000000 0010 0000
No ambiguity as each customer has unique prefix
Retains most of original address to allocate remaining to other customers
22
CIDR Host Address
Assume organization is assigned 128.211.0.16/28
Source: Douglas, C (2016) Computer Networks and Internets
23
Special IP Address
IP defines a set of address that are reserved; never assigned to hosts
Network Address
Directed Broadcast Address
Limited Broadcast Address
This Computer Address
Loopback Address
Source: Douglas, C (2016) Computer Networks and Internets
24
1. Network Address
IP reserves host address zero (all 0s in the suffix) to denote a network
Address 128.211.0.16/28 denotes a network as bits beyond 28 are 0s
A network address should never appear as the destination address in a packet
25
2. Directed Broadcast Address
When packet sent to directed broadcast address (DBA)
A copy of the packet travels across Internet until it reaches the specified network
Delivered to all hosts on the specific network
Directed broadcast address for a network is formed by adding a all 1s suffix to the prefix
Prefix: 10000000 11010011 00000000 0000000
Result: 10000000 11010011 11111111 11111111
26
DBA Requirements
If network hardware supports broadcast
directed broadcast will be delivered using the hardware broadcast capability
If a network does not have hardware support for broadcast
software must send a separate copy of the packet to each host on the network
27
3. Limited Broadcast Address
Limited broadcast: broadcast on directly-connected network
Normally used during system startup by computer that does not know network number
Limited broadcast address are 32-bits of 1s
IP will broadcast any packet sent to the all-1s address across the local network
28
4. This Computer Address
A computer needs to know its IP address before it can send or receive Internet packets
The startup protocols use an IP to communicate
To obtain IP address automatically when the computer boots
IP reserves the address that consists of all 0s to mean this computer
29
5. Loopback Address (1/2)
Loopback address used to test network applications
Used for preliminary debugging
Instead of executing each program on a separate computer
Runs both programs on a computer and use a loopback address when communicating
Programmers often use host number 1
127.0.0.1 is most popular loopback address
30
5. Loopback Address (2/2)
Allows testing the program logic quickly
IP reserves the network prefix 127/8 for use with loopback
During loopback testing no packet leaves computer
IP software forwards packets from one application to another
Never appears in a packet traveling across a network
31
Practice 19.2
For CIDR, how can an address be split into multiple subnetworks?
32
Lesson 19 Outline
IPv4 Addressing
Classless Addressing
Berkeley Address
IPv6 Addressing
33
Berkeley Broadcast Address
The University of California at Berkeley developed an early implementation of TCP/IP protocols
Berkeley Software Distribution (BSD)
BSD contained a nonstandard feature
Uses a host suffix of all 0s identical to the network address
this address form is known as Berkeley broadcast
34
Berkeley Contribution
Initially many computer manufacturers derived their early TCP/IP software from Berkeley implementation
Few still uses Berkeley broadcast today
TCP/IP implementations often include a configuration parameter
To select between TCP/IP standard and Berkeley form
35
Routers IP Address
Router has connections to multiple physical networks
Each IP address for a physical network
Each router is assigned two or more IP addresses
One address for each network attached
IP address does not identify a device but identifies a connection between a device and a network
36
Router IP Address Illustration
A device with multiple network like a router must be assigned one IP address for each connection
Source: Douglas, C (2016) Computer Networks and Internets
37
Multi-homed Hosts
A host computer with multiple network connections is said to be multi-homed
Multiple addresses, one for each network connection
Reliability: can reach the Internet through either connections
Performance: can send traffic directly and avoid routers that are sometimes congested
38
Lesson 19 Outline
IPv4 Addressing
Classless Addressing
Berkeley Address
IPv6 Addressing
39
IPv6 Addressing
IPv6 includes addresses with a multi-level hierarchy
highest level corresponds to an ISP
next level corresponds to an organization
next to a site
IPv6 defines a set of special addresses
does not include a special address for broadcasting on a given remote network
40
IPv6 Address Types
Packets will be only delivered to just one of a group of addresses
Nearest one, measured by routing protocol, will be chosen
Source: Douglas, C (2016) Computer Networks and Internets
41
Colon Hexadecimal Notation
IPv6 address occupies 128 bits represented in Colon hexadecimal notation (colon hex)
Reduce number of characters used to write addresses
Each group of 16 bits is written in hex with a colon separating groups
69DC : 8864 : FFFF : FFFF : 0 : 1280 : 8C0A : FFFF
42
Reading
Douglas, C. (2016). Computer Networks and Internets, Global Edition (6th ed.). Pearson Education. ISBN: 978-1292061177 Chapter 21, 24
43
End of Lesson
44
