Network Layer Protocols
A network’s computers can all be uniquely identified and addressed because of their IP addresses. Layer-3 (Network Layer) logical address is what an IP address is. Every time a computer restarts, this address might change. A computer may have a single IP address at one point in time and a different IP address at a different time.
ARP
- ARP stands for Address Resolution Protocol.
- The MAC address encoded on the NIC identifies every device connected to the network. As a result, we can state that devices on a local area network require the MAC address in order to communicate. It is simple to change a MAC address. For instance, when a machine’s NIC fails, the MAC address changes but the IP address does not. When an internet address is known, ARP is used to determine the node’s MAC address.
- It is used to associate an IP address with the MAC address.
How ARP works
The host broadcasts an ARP query packet that contains the IP address over the network if it wants to know the physical address of another host on its network. Only the intended recipient can identify the IP address and send back the physical address after every host on the network has received and processed the ARP packet. The host that is currently hosting the datagram adds the physical address to the datagram header and cache memory before sending it back to the sender.
Steps taken by ARP protocol
A device will take the following actions in order to communicate with another device:
- To determine whether a given IP address contains a corresponding MAC address or not, the device will first check its internet list, known as the ARP cache. Using the arp-a command, will use the command prompt to check the ARP cache.
- If the ARP cache is empty, the device broadcasts a request for a matching MAC address to every device on the network.
- When a device’s IP address matches, it will reply to the sender with its MAC address.
- Communication between two devices can start as soon as the device receives the MAC address.
- The MAC address is stored in the ARP cache if it is received by the device. Using the command arp -a in the command prompt, we can examine the ARP cache.
Internet Control Message Protocol (ICMP)
The network diagnostic and reporting protocol is called ICMP. ICMP is a member of the IP protocol family and employs IP as its carrier protocol. After ICMP packet construction, it is enclosed in an IP packet. ICMP is an unreliable best-effort protocol, just like IP.
Any network-related feedback is relayed back to the originating host. Through the use of ICMP, errors in the network are reported. Numerous diagnostic and error-reporting messages are included in ICMP.
The two ICMP messages that are most frequently used to determine whether end-to-end hosts are reachable are ICMP-echo and ICMP-echo-reply. A host is required to respond with an ICMP-echo-reply after receiving an ICMP-echo request. The ICMP will report any issues in the transit network if they arise.
Internet Protocol Version 4 (IPv4)
The TCP/IP host addressing mechanism uses the 32-bit addressing scheme known as IPv4. Every host on the TCP/IP network can be uniquely identified thanks to IP addressing.
By offering a hierarchical addressing scheme, IPv4 enables the creation of sub-networks, each with a specific number of hosts. Numerous categories are used to categorise IP addresses:
- Class A – For network addresses, it uses the first octet, and for host addressing, it uses the last three octets.
- Class B – first two octets are used for network addresses, and the final two are used for host addressing.
- Class C – The last octet is used for host addressing, and the first three are used for network addresses.
- Class D – In contrast to the hierarchical structure for addressing schemes above three, it offers a flat IP addressing scheme.
- Class E – It is used as an experimental.
Additionally, IPv4 has clearly defined address spaces for both private (not routable on the internet) and public addresses (provided by ISPs and routable on the internet).
Despite being unreliable, IP offers a “Best-Effort-Delivery” mechanism.
Internet Protocol Version 6 (IPv6)
A new generation of Internet Protocol, version 6, was created as a result of the exhaustion of IPv4 addresses. With 128-bit wide addresses for its nodes, IPv6 offers plenty of address space for use in the future across the entire planet or even further.
Despite eliminating broadcasting, IPv6 has added Anycast addressing. Devices can communicate within a subnet using an IPv6 address that they self-acquire thanks to IPv6. The dependability of Dynamic Host Configuration Protocol (DHCP) servers is eliminated by this auto-configuration. In this manner, communication between the hosts is still possible even if the DHCP server for that subnet is down.
The IPv6 mobility feature is a new feature. Mobile machines with IPv6 capabilities can move around without having to change their IP addresses.
Although still in its early stages, IPv6 is anticipated to completely replace IPv4 in the coming years. There are currently only a few networks using IPv6. For IPv6-enabled networks, there are some transitional mechanisms that allow for easy communication and network roaming on IPv4.
Which are:
- Dual stack implementation
- Tunnelling
- NAT-PT