![]() ![]() HTTP message was carried inside a TCP segment, which was carried Highlighted in the packet-listing window). The selected message (in this case the HTTP OK message, which is The packet-contents window shows details of ![]() The gaia.cs. web server) and the response message from the HTTP messages were captured: the GET message (from your browser to The above figure shows in the packet-listing window that two Your Wireshark window should look similar to the window shown Stop Wireshark packet capture and enter http as the Your browser should display the very simple, one-line HTMLÄ£. Start your browser and enter the following (clear In this question, you will practice the properties of HTTP ![]() This is called reassembly in Wireshark and your parser should do something similar too.Q1. Your parser needs to read the length of the PDU and it will need to keep reading TCP packets until all bytes of the PDU are received so that it can dissect it. However that length can be greater than the Maximum Segment Size (MSS), therefor the PDU will not fit into one packet as explained. Protocol Data Units (PDUs) of protocol X have a length header that indicate the length of the PDU. If I have read your question correctly, you are trying to parse a pcap file in which there are packets of protocol X which are transported over TCP. All segments are processed that way until the full PDU is received and the data can then be handed over to the application in one piece. ![]() The receiver then strips the ethernet/IP/TCP headers and places the TCP segment in the receive buffer. If TCP needs to sends a block of data (a higher layer Protocol Data Unit (PDU)) that is larger than this MSS, it will break up the PDU into smaller pieces of size MSS and send those segments as individual packets to the receiver. This is what is called the Maximum Segment Size (MSS). From this 1500 bytes, 20 bytes are needed for the IP header and 20 bytes are needed for the TCP header, leaving 1460 bytes for the TCP payload. This means ethernet can send 1500 bytes of data to another ethernet host. This is needed because every network has a finite maximum length per packet, this maximum length is called the Maximum Transmission Unit (MTU). Since TCP is a streaming protocol, the packet bounderies are just artificial cuts in the data stream. ![]()
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