IP адреса, часть 2 | Курс "Компьютерные сети"

IP Addresses: Types and Special Cases

Overview of IP Address Types

• The lecture introduces the topic of IP addresses, focusing on global network layer addresses within the TCP/IP protocol stack.

• Three main types of IP addresses are discussed: unicast (individual), multicast (group), and broadcast (all computers in a network).

Unicast, Multicast, and Broadcast Addresses

• A unicast address is assigned to a specific computer in the network; this was covered in the previous lecture.

• A multicast address allows data to be sent to multiple computers simultaneously that belong to a specific group.

• A broadcast address sends data to all computers within a single subnet. It retains the network part unchanged while setting all bits in the host part to 1.

Broadcast Address Formats

• Two scenarios for using broadcast addresses are explained: limited broadcast (within one subnet) and directed broadcast (to all devices in another subnet).

• Limited broadcasts use an address with all bits set to 1, ensuring packets do not pass through routers.

Special Types of IP Addresses

• Certain configurations for IP addresses are prohibited; an address with only zeros represents a network address, while one with only ones signifies a broadcast address.

• The special loopback address 127.0.0.0/8 is designated for testing applications without sending data over the network.

Link Local Addresses and Unique Global Addresses

• Link local addresses are automatically assigned by operating systems when no manual configuration is made; they function solely within their own subnet.

• To ensure unique global addressing across networks like the Internet, organizations must obtain permission from regional registrars for their allocated IP ranges.

Private Address Ranges

• For internal networks not connected to the Internet, private IP ranges have been established so that organizations can create networks without needing public IP allocations.

Understanding Private IP Addresses and NAT

Overview of Private IP Addresses

• Private IP addresses are used in networks that do not connect to the internet. They follow the guidelines set by RFC 1918, which includes ranges such as 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16.

• These private addresses are not routable on the internet, meaning they cannot be accessed directly from external networks.

Connecting Private Networks to the Internet

• To connect a network using private IP addresses to the internet, Network Address Translation (NAT) technology is employed.

• NAT replaces private subnet addresses with a real public IP address when accessing the internet.

The IPv4 Address Exhaustion Problem

• The IPv4 protocol uses a 32-bit address length, allowing for just over four billion unique addresses; this was sufficient during its initial design but has become inadequate due to global internet expansion.

• As nearly all IPv4 addresses have been allocated, obtaining a new IPv4 address is increasingly difficult.

Solutions to Address Shortage

• Two primary solutions exist:

• Transitioning to IPv6, which offers a significantly larger address space (128 bits).

• Implementing temporary solutions like MAC Address Translation within networks using private addressing schemes.

Types of IP Addresses in Networking

• There are three main types of IP addresses:

• Individual computer addresses for specific devices.

• Group addresses for multiple computers.

• Broadcast addresses intended for all devices within a subnet.

Unique Global Identification Requirement

• All public IP addresses must be unique globally; thus, permission must be obtained from organizations like ICANN (Internet Corporation for Assigned Names and Numbers).