Cybersecurity - Networking

Some terminology related to Networking

IP Addresses

IP addresses are broadly categorized into two types

1. IP v4
• In IP v4 - a 32 bit IP address
• format of IP address will be like A.B.C.D 
• a numeric IP address and binary bits are separated by . (dot)
• these are again categorized into public and private IP addresses
• Range of private IP addresses
1. Class A - 10.0.0.0 to 10.255.255.255
2. Class B - 172.16.0.0 to 172.31.255.255
3. Class C - 192.168.0.0 to 192.168.255.255
• offers a 12 header field
• Supports broadcast and has checksum field
2. IP v6
• In IP v6 - a 128 bit IP address
• an alphanumeric IP address and binary bits are separated by : (colon)
• offers a 8 header field
• Doesn't support broadcast and no checksum field

Some key ports to remember

Port number		Description
20	TCP	FTP data transfer
21	TCP	FTP Control
22	TCP/UDP	ssh
23	TCP	telnet
25	TCP	smtp
53		DNS
67		used by DHCP servers to listen for incoming DHCP client requests
68		used by the DHCP client to listen for messages from the DHCP server
80	TCP/UDP	Hypertext Transfer Protocol(http)
110	TCP	Post Office Protocol(POP3)
137	UDP	NetBIOS name service used for name registration and resolution
138	TCP/UDP	NetBIOS Datagram Service
143	TCP	Internet Message Access Protocol(IMAP)
389		LDAP
443	TCP	Hypertext Transfer Protocol over TLS/SSL(https)
3389	TCP/UDP	Microsoft Terminal Server(RDP)

Port numbers (specifically TCP ports):

A TCP port is an unsigned value and a total of 65,536 (0 to 65,535) ports will be available in a Server.

Port numbers are assigned in various ways, based on three ranges: 

1. System Ports/Well-known Ports (0-1023), 
2. User/Registered Ports (1024-49151), and 
3. Dynamic and/or Private Ports and/or Ephemeral (49152-65535); 

the different uses of these ranges is described in [RFC6335]. 

System Ports are assigned by IETF process for standards-track protocols, as per [RFC6335].  

User Ports are assigned by IANA using the "Expert Review" process, as per [RFC6335].  

Dynamic Ports are not assigned.