Cnp Quiz 4 (Cse A)

The fragmentation offset field helps to check the rearrangement of the fragments. This field indicates the position of the fragment within the original datagram. By comparing the fragmentation offsets of different fragments, the receiving device can determine the correct order in which the fragments should be reassembled to recreate the original datagram.

The Time to Live (TTL) field in an IP datagram represents the maximum number of hops (routers) that the datagram can pass through before being discarded. In this case, the TTL value is 10, which means that the datagram can be processed by a maximum of 10 routers. Once the datagram reaches the 11th router, it will be discarded as the TTL value will be reduced to 0. Therefore, the correct answer is 10.

To determine the number of the last byte in a fragment, we need to consider all the given factors. HLEN (Header Length) is important because it tells us the length of the IP header, which is necessary for calculating the position of the fragment within the original IP packet. The fragmentation offset is needed to determine the position of the fragment relative to the original packet. Lastly, the total length of the fragment is crucial in determining the number of the last byte. Therefore, all the given factors (HLEN, fragmentation offset, and total length) are necessary to determine the number of the last byte in a fragment.

In IPv4 layer, the datagram is of variable length. This means that the size of the datagram can vary depending on the amount of data being transmitted. Unlike fixed length datagrams, variable length datagrams allow for more flexibility in terms of the amount of data that can be sent in a single packet. This is important as it allows for efficient utilization of network resources by adjusting the packet size based on the amount of data being sent.

In IP fragmentation, a datagram is divided into smaller fragments to be transmitted over a network. Each fragment retains the same identification field as the original datagram. This allows the receiving end to reassemble the fragments correctly based on the identification field. Therefore, the statement that the identification field is the same for all three datagrams is true.

A router reads the IP address on a packet to determine the next hop. The IP address is a unique identifier assigned to each device on a network, and it helps the router determine the destination of the packet and the appropriate path to forward it. The MAC address, on the other hand, is used for communication within a local network and is not relevant for determining the next hop. The source address is the address of the sender, and ARP is a protocol used to map IP addresses to MAC addresses.

The given answer indicates that the third IP fragment generated by the router has a MF (More Fragments) bit value of 0, indicating that it is the last fragment of the original IP packet. The Datagram Length field is 1444 bytes, which includes the IP header length of 20 bytes. The Offset field is 370, indicating the position of the fragment within the original IP packet.

In a loose source route, the datagram must visit each router in the list, but it is allowed to visit other routers as well. This means that the datagram has some flexibility in its routing path, as long as it visits all the routers specified in the list. This is different from a strict-source route, where the datagram must strictly follow the specified path without deviation. The No-Operation Option and Timestamp options are unrelated to the concept of visiting routers, so they do not fit the description. Therefore, the correct answer is Loose source route.

If the destination receives a datagram that did not visit one of the routers listed in the strict-source-route option field, it simply discards the datagram. This means that the destination does not process or forward the datagram further, and it is effectively dropped or ignored.

The number of the first byte can be calculated by multiplying the value of the fragmentation offset by 8. In this case, the fragmentation offset is 200, so the number of the first byte would be 200 * 8 = 1600.

When fragmentation occurs in IPv4, the fields that are changed in the header are the Total length, M bit of flag, Fragmentation offset, TTL, and Header Checksum. The Total length field is updated to reflect the new length of the fragmented packet. The M bit of flag is set to indicate whether there are more fragments or not. The Fragmentation offset field specifies the position of the fragment within the original packet. The TTL (Time to Live) field is decremented to indicate the remaining number of hops the packet can take. Finally, the Header Checksum field is recalculated to ensure data integrity.

The field in the IPv4 header that allows the de-multiplexing process when a datagram reaches the destination host is the Protocol field. This field specifies the protocol used in the data portion of the IP packet, such as TCP, UDP, ICMP, etc. When the datagram arrives at the destination host, the Protocol field is examined to determine which higher-level protocol should handle the data. This allows the destination host to correctly deliver the packet to the appropriate application or service.

When the record-route option is being used, an intermediate router inserts the IP address of its outgoing interface. This is because the record-route option allows a packet to record the IP addresses of each router it passes through. By inserting its outgoing interface IP address, the router is indicating the specific interface through which the packet is being forwarded. This information can be useful for troubleshooting network issues or analyzing the path taken by a packet.

The payload can appear after the option "end-of-option" in an IPv4 datagram. The payload refers to the actual data that is being transmitted in the datagram. It can include any information or message that needs to be sent from the source to the destination. The options mentioned in the question, such as no-operation option, end-of-option option, and timestamp option, are all additional features or fields that can be included in the datagram, but the payload is the main content of the message.

The maximum possible size of the data portion of the IPv4 datagram is 65,515 bytes. This is because the maximum size of an IPv4 datagram, including both the header and the data, is 65,535 bytes. The header of an IPv4 datagram is 20 bytes, so the remaining 65,515 bytes are available for the data portion.