IPv4 Addressing - Unicast Addressing

What is Unicast Addressing?

Unicast addressing is a method of communication where data is sent from one source device to one specific destination device over a network.

Why is Unicast Addressing useful?

Unicast is the most common form of network communication. It is efficient for one-to-one data exchanges like web browsing, file transfers, and emails.

How it works?

In unicast communication, each packet contains the unique IP address of the destination device. Routers forward the packet based on this address to reach the correct recipient.

Where is Unicast Addressing used?

Unicast is used in most standard internet and network communications, including HTTP, FTP, SSH, VoIP, and more.

Which OSI layer does this protocol belong to?

Unicast addressing operates at the Network Layer (Layer 3) of the OSI model, using IP for addressing and routing.

Is Unicast Addressing Windows specific?

No, unicast addressing is not Windows specific. It is universally supported across all platforms that implement the IP protocol.

Is Unicast Addressing Linux specific?

No, unicast addressing is not Linux specific. It is supported by all network-capable operating systems, including Linux, Windows, and macOS.

Which Transport Protocol is used by Unicast Addressing?

Unicast can use both TCP and UDP transport protocols depending on the application requirements.

Which Port is used by Unicast Addressing?

Unicast addressing itself does not define any specific port. The port number depends on the application or service being used (e.g., HTTP uses port 80).

Is Unicast Addressing using client-server model?

Yes, unicast is often used in client-server communication, where a client sends requests to a specific server, and the server responds directly to that client.

What is the difference between unicast and multicast?

Unicast sends data to a single specific device, while multicast sends data to a group of devices subscribed to a multicast address.

What is the difference between unicast and broadcast?

Unicast targets one device; broadcast sends data to all devices on the local network.

Can unicast addressing be used over the internet?

Yes, unicast is the standard communication method on the internet, sending data from one host to another.

Does unicast addressing consume more bandwidth than multicast?

Typically yes, because unicast sends separate copies to each recipient, while multicast sends a single stream to multiple devices.

How does unicast addressing handle data loss?

Protocols like TCP provide error checking and retransmission to ensure reliable delivery over unicast.

Is unicast addressing scalable?

It can be less scalable for one-to-many communication because it requires individual transmissions to each receiver.

What is the address range for IPv4 unicast addresses?

Most IPv4 addresses, except those reserved for multicast and broadcast, are unicast addresses.

Are MAC addresses used in unicast communication?

Yes, at Layer 2, unicast communication uses unique MAC addresses to identify devices on the local network.

Does unicast addressing support both IPv4 and IPv6?

Yes, unicast addressing exists in both IPv4 and IPv6 protocols.

Can unicast addressing be used in peer-to-peer networks?

Yes, unicast allows direct device-to-device communication without intermediaries.

What role does DNS play in unicast addressing?

DNS translates domain names to unicast IP addresses, enabling devices to locate specific hosts.

Is unicast addressing affected by NAT?

Yes, NAT modifies IP addresses, but unicast communication continues through address translation.

How does unicast addressing impact network security?

Since unicast targets specific devices, it can be secured with firewalls and access control lists.

Can unicast packets be intercepted?

Yes, but encryption protocols like TLS help protect data confidentiality.

What is a unicast routing table?

A routing table that stores paths to individual destination IP addresses.

Does unicast addressing require session establishment?

Not inherently; session establishment depends on the transport protocol used, such as TCP.

What is a unicast IP address example?

An example is 192.168.1.10, assigned to a single device on a network.

How do routers forward unicast packets?

Routers use the destination IP in the packet header and their routing tables to forward packets toward the intended device.

Topics in this section,

  • In this section, you are going to learn

  • Terminology

  • Version Info

  • rfc details

Objective

Verify one-to-one communication on the subnet.

Test Setup

  • Hardware: Three virtual machines (VM1, VM2, Sender VM)

  • Network Configuration: All VMs connected to the same virtual network

    • VM1: 192.168.1.10/24

    • VM2: 192.168.1.20/24

    • Sender: 192.168.1.30/24

Note

Ensure all VMs are on the same subnet. Only the target IP should receive the packet.

VM Configuration

# VM1
test:~$ sudo ip addr add 192.168.1.10/24 dev enp0s8
test:~$ sudo ip link set enp0s8 up

# VM2
test:~$ sudo ip addr add 192.168.1.20/24 dev enp0s8
test:~$ sudo ip link set enp0s8 up

# Sender VM
test:~$ sudo ip addr add 192.168.1.30/24 dev enp0s8
test:~$ sudo ip link set enp0s8 up
test:~$ ping 192.168.1.10
PING 192.168.1.10 (192.168.1.10) 56(84) bytes of data.
64 bytes from 192.168.1.10: icmp_seq=1 ttl=64 time=4.97 ms
64 bytes from 192.168.1.10: icmp_seq=2 ttl=64 time=0.827 ms
64 bytes from 192.168.1.10: icmp_seq=3 ttl=64 time=1.04 ms
64 bytes from 192.168.1.10: icmp_seq=4 ttl=64 time=1.50 ms
64 bytes from 192.168.1.10: icmp_seq=5 ttl=64 time=0.737 ms
64 bytes from 192.168.1.10: icmp_seq=6 ttl=64 time=1.46 ms
64 bytes from 192.168.1.10: icmp_seq=7 ttl=64 time=0.887 ms
64 bytes from 192.168.1.10: icmp_seq=7 ttl=64 time=0.887 ms
64 bytes from 192.168.1.10: icmp_seq=8 ttl=64 time=0.979 ms
64 bytes from 192.168.1.10: icmp_seq=9 ttl=64 time=0.548 ms
64 bytes from 192.168.1.10: icmp_seq=10 ttl=64 time=1.08 ms
64 bytes from 192.168.1.10: icmp_seq=11 ttl=64 time=0.898 ms
64 bytes from 192.168.1.10: icmp_seq=12 ttl=64 time=0.865 ms
64 bytes from 192.168.1.10: icmp_seq=13 ttl=64 time=0.839 ms
64 bytes from 192.168.1.10: icmp_seq=14 ttl=64 time=1.10 ms
64 bytes from 192.168.1.10: icmp_seq=15 ttl=64 time=0.797 ms
64 bytes from 192.168.1.10: icmp_seq=16 ttl=64 time=0.544 ms
64 bytes from 192.168.1.10: icmp_seq=17 ttl=64 time=1.10 ms
64 bytes from 192.168.1.10: icmp_seq=18 ttl=64 time=0.692 ms
64 bytes from 192.168.1.10: icmp_seq=19 ttl=64 time=1.15 ms
64 bytes from 192.168.1.10: icmp_seq=20 ttl=64 time=0.914 ms
64 bytes from 192.168.1.10: icmp_seq=21 ttl=64 time=0.688 ms
64 bytes from 192.168.1.10: icmp_seq=22 ttl=64 time=0.533 ms
64 bytes from 192.168.1.10: icmp_seq=23 ttl=64 time=0.839 ms
64 bytes from 192.168.1.10: icmp_seq=24 ttl=64 time=0.980 ms
^C
--- 192.168.1.10 ping statistics ---
24 packets transmitted, 24 received, 0% packet loss, time 23249ms
rtt min/avg/max/mdev = 0.533/1.082/4.967/0.845 ms

Capture Analysis

  • Wireshark on VM1: Shows ICMP Echo Request and Reply.

  • Wireshark on VM2: No packets observed (not the intended recipient).

  • Wireshark on Sender: Shows outgoing Echo Request and incoming Echo Reply.

Wireshark Captures - VM1 Capture - VM2 Capture - Sender Capture

  • packet details

  • usecases

  • features

  • Reference links