This is (8th Article) in continuation of our last one article, a new series of networking articles. In this segment, we are going to discuss how address resolution takes place between IPv4 and IPv6, Bootstrap Protocol and also, we will try to understand the role of DHCP in networking.
IPv4 and IPv6 address spaces are of different sizes. Address notations for the two are also different. The IPv6 address of 128 bits is represented by hexadecimal colon notation. 128 bits are divided into eight segments. Each of the segments is separated by a colon. As an example, EFEF:1234:DCEE:7676:1C2C:00FE:ABOO:D8B9 represents one IPv6 address.
The notion allows for dropping leading zeros. As in the example, 00FE can be just FE. Moreover, IPv6 frames provide many flexibilities and options over IPv4 frames. One example of IPv4 address representation of 32 bits is 188.8.131.52, a representation of dot-separated four bytes.
Therefore, deployment of IPv6 requires some techniques of compatibility to make IPv6 coexist and co-operate with the existing vast IPv4 network. After all, it is neither technically-feasible nor economically viable to upgrade all the existing millions of machines of IPV4 to IPv6.
Two schemes used for compatibility are Dual Stack and Tunnelling etc.
Dual-Stack offers a technique where all nodes in any network are both IPv4 and IPv6 enabled. While deploying, IPv6 nodes can be made backward-compatible, making them capable of sending IPv4 datagram, too.
However, already existing IPv4 nodes are not capable of sending IPv6 datagram. In dual-stack, each node is made IPv6/IPv4-compatible. The node also has the capability to determine whether the next node of routing is IPv4 or IPv6 which is done by the Domain Name System (DNS). Until and unless the entire world switches to IPv6, dual-stack will remain one of the top methods for address resolution and a solution for resolving incompatibilities.
In Dual Stack, any node of IPv6 duly sends IPv6 datagram to the next node, if that node is of IPv6. But if the next node is of IPv4, the received IPv6 datagram is converted to IPv4 datagram before transmitting. By the process of conversion, a lot of information on the original IPv6 datagram is lost. This is a major disadvantage of dual-stack.
In Tunnelling, any node, when transmitting IPv6 datagram to IPv4 node, treats the whole IPv6 datagram as payload. With this payload, a new IPV4 datagram is made. IPv4 nodes treat all IPv6 packets as complete payloads for subsequent transmission in tunneling. In the process, information on IPv6 datagram is preserved.
However, as under tunneling, IPv6 datagram is repackaged for transmission over IPv4, it is done with an encryption standard to hide the nature of the original datagram while running through the tunnel.
Bootstrap Protocol (BOOTP) is used to provide additional information to a caller. BOOTP message goes as a payload of the UDP layer.
When a device or any computer connected to a network is powered up and boots its operating system, the system generates a broadcast BOOTP message. The message is a request for an IP address. A BOOTP configuration server assigns the IP address based on request. With the start of the BOOTP procedure, when a request is sent to the server, a timer is turned on. If no reply is received within the defined time period, BOOTP should attempt retransmission. BOOTP is implemented with UDP as a transport protocol. It works only with IPv4 networks.
Dynamic Host Configuration Protocol
IPv4 address is a stateful address. This means that, if a node moves from one subnet to another, the user has to either reconfigure the IP address or request for a new IP address from dynamic host configuration protocol (DHCP). DHCP is a network management protocol used over UDP/IP networks. A DHCP server dynamically assigns IP addresses and other network parameters to each of the devices connected to a network.
Whereas, IPv6 supports a stateless autoconfiguration address. Thus, with IPv6, while moving from a subnet to another, a host can generate its own IP address. This is done by the host by adding its Media Access Control (MAC) physical address to the subnet prefix.
When a host attempts to get an IP address, a DHCPDiscover message is broadcast over the physical network, and the DHCP server in the network replies with a DHCP offer message.
The Offer message provides an IP address and other information related to configuration. Every network need not have a DHCP server. A network may have a DHCP relay agent, which requests the remote server for a reply to be subsequently sent to the requesting host. If the requesting host receives many offers from a number of DHCP servers, it will accept one offer and acknowledge the same to the corresponding server, which then acknowledges the reply of the host. Then, the host uses the IP address for communication.
Advantages of DHCP in networking
1. Precise IP configuration: The IP address configuration parameters must be precise and when managing inputs, for example, “192.168.159.3”, it’s easy to commit an error. Typographical errors are normally hard to investigate and the use of a DHCP server limits that hazard.
2. Diminished IP address conflicts: Each associated device must have an IP address. In any case, each address must be used once and a copy address will bring about a conflict where either of the devices can not be associated. This can happen when addresses are assigned out manually, especially when there are countless endpoints that just associate intermittently, for example, cell phones. The use of DHCP guarantees that each address is just used once.
3. Automation of IP address service: Without DHCP, network service would need to allot addresses manually. Monitoring which device has what address can be a pointless activity as it’s almost difficult to comprehend when devices expect access to the system and when they leave. DHCP permits this to be computerized and centralized so network experts can deal with all areas from a solitary area.
4. Efficient change management: The use of DHCP makes it easy to change addresses. For instance, an organization might need to change its IP addressing technique with one territory then onto the next. The DHCP server is arranged with the new data and the data will be proliferated to the new endpoints. Essentially, if a network device is updated and supplanted, no network system configuration is required.
This is enough for this section; we have talked about the idea of Dual Stack and Tunneling between IPv4 and IPv6 and the role of DHCP in networking. In the next article, we will take a look at Mobile IP in networking.
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