42cursus - netwhat

Table of Contents

1. Internet Protocol (IP)
2. Netmask
3. Transmission Control Protocol (TCP)
4. User Datagram Protocol (UDP)
5. Open Systems Interconnection (OSI) Model
6. Dynamic Host Configuration Protocol (DHCP)
7. Domain Name System (DNS)
8. Ping

Internet Protocol (IP)

• IPv4 addresses are 32 bits long (4,294,967,296 or 2^32 addresses)
• IPv6 addresses are 128 bits long (3.4E38 addresses)

IPv4 Address Classes

Class	Address Range	Number of Networks	Addresses per Network	Number of Addresses
Class A	0.0.0.0 - 127.255.255.255	128 (2^7)	16,777,216 (2^24)	2,147,483,648 (2^31)
Class B	128.0.0.0 - 191.255.255.255	16,384 (2^14)	65,536 (2^16)	1,073,741,824 (2^30)
Class C	192.0.0.0 - 223.255.255.255	2,097,152 (2^21)	256 (2^8)	536,870,912 (2^29)
Class D	224.0.0.0 - 239.255.255.255	Undefined	Undefined	268,435,456 (2^28)
Class E	240.0.0.0 - 255.255.255.255	Undefined	Undefined	268,435,456 (2^28)

IPv4 Address Binary Code Representation

Class	Dot-Decimal Notation	Binary Code
Class A	0.0.0.0	00000000.00000000.00000000.00000000
	127.255.255.255	01111111.11111111.11111111.11111111
		0nnnnnnn.HHHHHHHH.HHHHHHHH.HHHHHHHH
Class B	128.0.0.0	10000000.00000000.00000000.00000000
	191.255.255.255	10111111.11111111.11111111.11111111
		10nnnnnn.nnnnnnnn.HHHHHHHH.HHHHHHHH
Class C	192.0.0.0	11000000.00000000.00000000.00000000
	223.255.255.255	11011111.11111111.11111111.11111111
		110nnnnn.nnnnnnnn.nnnnnnnn.HHHHHHHH
Class D	224.0.0.0	11100000.00000000.00000000.00000000
	239.255.255.255	11101111.11111111.11111111.11111111
		1110XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX
Class E	240.0.0.0	11110000.00000000.00000000.00000000
	255.255.255.255	11111111.11111111.11111111.11111111
		1111XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX

• n indicates a bit used for the network ID
• H indicates a bit used for the host ID
• X indicates a bit without a specified purpose

Private IPv4 Addresses

1. 10.0.0.0 - 10.255.255.255
2. 172.16.0.0 - 172.31.255.255
3. 192.168.0.0 - 192.168.255.255

Netmask

• 32-bit binary mask used to divide an IPv4 address into subnets
• First address in the subnet is the assigned network address (all-bits-zero host value)
• Last address in the subnet is the assigned broadcast address (all-bits-one host value)

IPv4 Address Default Netmask

Class	Default Netmask	CIDR Notation
Class A	255.0.0.0	/8
Class B	255.255.0.0	/16
Class C	255.255.255.0	/24
Class D	Undefined	Undefined
Class E	Undefined	Undefined

Example 1: 10.21.145.137/13

	Dot-Decimal Notation	Binary Code
Address	10.21.145.137	00001010.00010 101.00101101.10001001
Netmask	255.248.0.0	11111111.11111 000.00000000.00000000
Network	10.16.0.0	00001010.00010 000.00000000.00000000
HostMin	10.16.0.1	00001010.00010 000.00000000.00000001
HostMax	10.23.255.254	00001010.00010 111.11111111.11111110
Broadcast	10.23.255.255	00001010.00010 111.11111111.11111111
Next Network	10.24.0.0	00001010.00011 000.00000000.00000000

• 10.21.145.137/13 belongs to the subnet 10.16.0.0 - 10.23.255.255
• Number of hosts in the subnet = 524286 (2^19 - 2)

Example 2: 156.67.154.75/28

	Dot-Decimal Notation	Binary Code
Address	156.67.154.75	10011100.01000011.10011010.0100 1011
Netmask	255.255.255.240	11111111.11111111.11111111.1111 0000
Network	156.67.154.64	10011100.01000011.10011010.0100 0000
HostMin	156.67.154.65	10011100.01000011.10011010.0100 0001
HostMax	156.67.154.78	10011100.01000011.10011010.0100 1110
Broadcast	156.67.154.79	10011100.01000011.10011010.0100 1111
Next Network	156.67.154.80	10011100.01000011.10011010.0101 0000

• 156.67.154.75/28 belongs to the subnet 156.67.154.64 - 156.67.154.79
• Number of hosts in the subnet = 14 (2^4 - 2)

Transmission Control Protocol (TCP)

• Connection-oriented protocol
• Does not support broadcasting
• Comparatively slower than UDP
• Reliable and guarantees delivery of data to destination
• Sequences data; packets arrive in-order at the receiver
• Extensive error checking mechanism; provides flow control & acknowledgment of data

User Datagram Protocol (UDP)

• Datagram-oriented protocol
• Supports broadcasting
• Faster, simpler & more efficient than TCP
• Delivery of data to destination cannot be guaranteed in UDP
• No sequencing of data; has to be managed by application layer if ordering is required
• Only has basic error checking mechanism using checksums

Open Systems Interconnection (OSI) Model

1. Application Layer
2. Presentation Layer
3. Session Layer
4. Transport Layer
5. Network Layer
6. Data Link Layer
7. Physical Layer

Dynamic Host Configuration Protocol (DHCP)

• Used for both IPv4 & IPv6
• Uses UDP as its transport protocol
• Automates IP configuration, including IP address, subnet mask, default gateway & DNS information

Domain Name System (DNS)

• Translates internet domain and host names to IP address

Ping

• Operates by sending Internet Control Message Protocol (ICMP) echo request packets to target host and waiting for ICMP echo reply
• ping localhost or ping 127.0.0.1 to test IP stack