Network Identifiers

PORT-Number

Identifies which process is using the network within a system
0 -> 1024 are called Well defined as they are used for predefined services
- HTTP -> 80
- HTTPS -> 443
- DNS -> 53
1024 -> 65535 are called ephemeral since, they are not preassigned and we can use it for our purposes.
When a device receives a packet, the port number defines, to which process the packet should be given

Two types
- Public
  - Known to everyone
  - Globally unique
  - Assigned by ISP
  - Not free
  - Router have a public IP
- Private
  - Used only in local/private network
  - Unique only inside a local network
  - Assigned by Router
  - Free
  - Not directly accessible from the internet
Versions of IP
- IPv4
  - 32 bit: represented as 4 octets -> 192.168.1.1
  - each part can vary from 0 to 255
- IPv6
  - 128 bit: represented in hexadecimal -> 2001:0db8:85a3::8a2e:0370:7334
Routers acts as a DHCP servers (Dynamic Host Configuration Protocol DHCP) and assigns IP to devices
Routers acts as a NAT NAT also translating IPs
It identifies to which local network (router), the packet should be send. From the IP address, the router can understand to which router the packet should be forwarded.
Works in Network Layer