Answer to Question #314554 in Computer Networks for Sunny

Question

Mention and explain each field of IPv4 header in detail, by taking suitable examples.

Answer 1

• Version: The first header field is a 4-bit version indicator. In the case of IPv4, the value of its four bits is set to 0100, which indicates 4 in binary.
• Internet Header Length: IHL is the 2^nd field of an IPv4 header, and it is of 4 bits in size. This header component is used to show how many 32-bit words are present in the header.
• Type of Service: ToS is also called Differentiated Services Code Point or DSCP. This field is used to provide features related to service quality, such as for data streaming or Voice over IP (VoIP) calls. It is used to specific how a datagram will be handled.
• Explicit Congestion Notification: ECN is used to send notifications to the sender or receive in situations where network congestion happens.
• Total Length: This field’s size is 16 bit, and it is used to denote the size of the entire datagram. The minimum size of an IP datagram is 20 bytes, and at the maximum, it can be 65,535 bytes.
• Identification: The identification or ID field in a packet can identify an IP datagram’s fragments uniquely.
• Flags: flag in an IPv4 header is a three-bit field that is used to control and identify fragments.
• Fragment Offset: This field is 13 bit long in length, and it is measured by blocks that units of 8-byte blocks. These are used to specify the offset of a fragment relative to the start of the IP datagram, which when it was not fragmented.
• Time to live: Time to live (TTL) is an 8-bit field to indicate the maximum time the datagram will be live in the internet system. The time here is measured in seconds, and in case the value of TTL is zero, the datagram is erased.
• Protocol: This is a filed in the IPv4 header reserved to denote which protocol is used in the data portion of the datagram
• The header’s checksum: The checksum field is of 16-bit length, and it is used to check the header for any errors. The header is compared to the value of its checksum at each hop, and in case the header checksum is not matching, the packet is discarded.
• Source Address: It is a 32-bit address of the source of the IPv4 packet.
• Destination Address: the destination address is also 32 bit in size, and it contains the receiver’s address.
• Options: This is an optional field of the IPv4 header. It is used only when the value of IHL is set to more than 5. These options contain values and settings for things related to security.