This pseudo header contains the Source Address, the Destination Address, the Protocol, and TCP length. This gives the TCP protection against misrouted segments. This information is carried in the Internet Protocol and is transferred across the TCP/Network interface in the arguments or results of calls by the TCP on the IP.

Efficiency (e) = useful/total = (Data without header)/(Data with header) Throughput = e * B { where B is bottleneck bandwidth } Example – An IP router with a Maximum Transmission Unit (MTU) of 200 bytes has received an IP packet of size 520 bytes with an IP header of length 20 bytes. The values of the relevant fields in the IP header. Chapter 5. The Internet Protocol (IP) - Shichao's Notes The Internet Protocol (IP) The Internet Header Length (IHL) field is the number of 32-bit words in the IPv4 header, including any options. Because this is also a 4-bit field, the IPv4 header is limited to a maximum of fifteen 32-bit words or 60 bytes. UDP Protocol | UDP Header | UDP Header Format | Gate Vidyalay

IP Packet Structure -

Chapter 5. The Internet Protocol (IP) - Shichao's Notes

UDP Header- The following diagram represents the UDP Header Format- 1. Source Port- Source Port is a 16 bit field. It identifies the port of the sending application. 2. Destination Port- Destination Port is a 16 bit field. It identifies the port of the receiving application. 3. Length- Length is a 16 bit field.

So the ip header says 519 ,So subtract 20 Bytes of ip header and 20 bytes of tcp header . The HTTP message length = 519 -20- 20 = 479 bytes. Note :I have shown the http as application it can be any other application its decodes based on destination port. And if any application is UDP over IP insted of TCP then subtract 8 bytes as Lenght of UDP IP Fragmentation in Detail - Packet Pushers The Total Length field (16 bits) changes based on the reduced size of the data in a fragment (plus IP header) which equals or is smaller than the MTU. Because the Fragment Offset field in the following fragments must be a multiple of 8 the fragment’s size isn’t always as large as the MTU allows. IP Datagram, Fragmentation and Reassembly IP Packet Header • Header Length (in 32 bit words) – Indicates end of header and beginning of payload – If no options, Header length = 5 Total Length in bytes (16) Time to Live (8) Options (if any) Bit 0 Bit 31 Version (4) Hdr Len (4) TOS (8) Identification (16 bits) Flags (3) Fragment Offset (13) Source IP Address Destination IP Address