IP Address

IP addresses are 32 bits (4 bytes) split into 4 chunks. Obviously $2^{32}$ is an incredibly large address space so we compress the table using IP prefixes.

It is generally recognized that the current approach of using the IP address as a locator and as an identifier was a poor design choice. (Clark, 2018, “Designing an Internet”)

IPv4

Special Addresses

1. First address (generally all 0s): network itself, or not assigned
2. Last address (generally all 1s): broadcast

CIDR Notation

IP/# where # is the number of bits in the network ID

e.g. 18.0.0.0/8 means first 8 bits are network ID, and 18.x.x.x is the space of all possible addresses ($2^{3\ast 8}=2^{24}$)

By default, routers will take the most specific one (longest network ID).

To prevent loops, we set a TTL (time-to-live) for packets to expire after a certain time.