What is the value in the Identification field and the TTL field? Identification: TTL: Do these values remain unchanged for all of the ICMP TTL-exceeded replies sent to your computer by the nearest (first hop) router? Why? The identification field changes for all the ICMP TTL-exceeded replies because the identification field is a unique value.
2 ICMP TTL exceeded reply, IP information 8. Describe the pattern you see in the values in the Identification field of the IP datagram The pattern is that the IP header Identification fields increment with each ICMP Echo (ping) request.ģ Fig. Which fields stay constant? Which of the fields must stay constant? Which fields must change? Why? The fields that stay constant across the IP datagrams are: Version (since we are using IPv4 for all packets) header length (since these are ICMP packets) source IP (since we are sending from the same source) destination IP (since we are sending to the same dest) Differentiated Services (since all packets are ICMP they use the same Type of Service class) Upper Layer Protocol (since these are ICMP packets) The fields that must stay constant are: Version (since we are using IPv4 for all packets) header length (since these are ICMP packets) source IP (since we are sending from the same source) destination IP (since we are sending to the same dest) Differentiated Services (since all packets are ICMP they use the same Type of Service class) Upper Layer Protocol (since these are ICMP packets) The fields that must change are: Identification(IP packets must have different ids) Time to live (traceroute increments each subsequent packet) Header checksum (since header changes, so must checksum) 7. Which fields in the IP datagram always change from one datagram to the next within this series of ICMP messages sent by your computer? Identification, Time to live and Header checksum always change. The more fragments bit = 0, so the data is not fragmented. Has this IP datagram been fragmented? Explain how you determined whether or not the datagram has been fragmented.
There are 20 bytes in the IP header, and 56 bytes total length, this gives 36 bytes in the payload of the IP datagram.Ģ 4. How many bytes are in the IP header? How many bytes are in the payload of the IP datagram? Explain how you determined the number of payload bytes. What is the IP address of your computer? The IP address of my computer is Within the IP packet header, what is the value in the upper layer protocol field? Within the header, the value in the upper layer protocol field is ICMP (0x01) 3. 1 ICMP Echo Request message IP information 1.
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