Tcp

Wireshark is a free program for analyzing and graphically presenting data protocols (sniffer). Such data protocols are used by computers on various communication media such as the local network or USB. Capturing the communication can be useful for troubleshooting or evaluating the content of the communication. Wireshark displays both the protocol headers and the transported content during a capture. The program relies on the output of small helper programs like pcap or usbpcap for the graphical presentation, in order to capture the communication content on the respective transmission medium. [wikipedia] ...

Transport Layer Security (TLS) known as Secure Sockets Layer (SSL) is an encryption protocol (based on x.509) for secure data transmission. Datagram Transport Layer Security (DTLS) is based on TLS and uses UDP instead of TCP. The difference between TLS and DTLS is equivalent to the difference between TCP and UDP. TLS requires the reliability of the data, among other things for decrypting data. If, for example, the data packets arrive out of order, TLS will not be able to perform an integrity check, since the check involves the sequence number of the packets, i.e. after packet N, packet N+1 is expected. ...

IPv4 Review IPv4 Header Version: 4 IHL (Internet Header Length): length of the header in 32-bit increments. Value 5 = 5 lines x 32 bits TOS (Type of Service): used to prioritize the IP packet (QoS) Total Length: 65535 bytes Identification, Flags & Fragment Offset. Control of fragmentation Flags: Bit 0 is reserved. If bit 1 is set to 0, fragmentation is allowed. If set to 1, not allowed. If bit 2 is set to 0, then it is the last fragment. If 1, more fragments follow. Time to Live: lifetime of the packet. Each router reduces the value by 1 Protocol: e.g. TCP, UDP, ICMP, etc. Header Checksum: checksum. Rarely used. Source / Destination: destination and source address IPv4 & IPv6 Header Differences ...