This packet is referred to as a SYN/ACK packet. Furthermore the response contains the controls bits SYN and ACK set and the Sequence number is set to the Servers PRNG number. The response sets the Acknowledgement field with the Sequencer number of the client with the number 1 added to it. Server receives the packet, reads the Sequence Number from the Client and crafts a response.This packet is referred to as a SYN packet. The Network Layer (Layer 3) allows the packet to be sent to a remote system. Client initiates the communication by sending a packet with the control bit SYN set in the header, a PRNG number in the Sequence number field and a target destination port.The handshake enforces that both parties intends to communicate.Įxplanation on how TCP engages in communications: The handshake uses 32 bits of PRNG ("Pseudo Random Number Generator") numbers to establish the handshake. TCP uses a three-way handshake to allow two systems to engage in communications. The other headers also play an important part, but outside of the security course. We can also see the control bits used to indicate what kind of packet it is. The Sequence and Acknowledgement numbers are used in the three-way handshake and to reliably transfer data.
We can see the graphic showing 16 bits for both source and destination ports, this is the same for for UDP. In the picture below we can see a TCP packet and how it would look like for anyone inspecting traffic on the network. A port, as indicated with a number between 5, dictates which network service should process the request. Just like IP uses IP addresses for addressing, TCP and UDP uses ports. There are also many other protocols in use in networks, all which have the potential of having security risks associated with them. The networks we are using consists of multiple protocols, some which are featured in this class. In this section we will go deeper into the protocols which are used in most networks. Several different technologies are in place to enable computers to talk over different kinds of networks. Computer systems often needs to talk to other systems this is done by putting them on the same network.
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