ccna syllabus 200 301

ccna syllabus 200 301.Figure 8.1 Connection MultiplexingOf course, the situation will be more complicated if multiple target devices are involved. In the example shown in Figure 8.1, PC-B also has a session to the server, and this connection has a source port of 50000 and a destination port of 23 - a Telnet connection. This raises an interesting question: how does the server distinguish between its connections to PC-A and PC.B? Because both connections have port numbers 50000/23o In fact, when multiplexing a session, the server uses not only the transport layer port number, but also the Layer 3 IP address of the device associated with the session. In this example, notice that PC-A and PC-B have different Layer 3 addresses: 1.1.1.1 and 1.1.1.2, respectivelyoFigure 8.2 shows a simple example of using port numbers between two computers OPC-A opens two Telnet sessions to PC.B; notice that their source port numbers are different, allowing PC-A to distinguish between the two Telnet sessions. When sending data to PC-B, the destination port number is 23, which tells PC.B which application to give the data segment to for processing. Note that when returning data from PC.B to PC-A, the port numbers are reversed, letting PC-A know which application (Telnet) and which session the data came from. Exam Point.Regardless of which devices are involved in a session, and regardless of how many sessions there are, the host is able to easily distinguish between sessions based on the source and destination ports and the source and destination IP addresses.Source Port = 50,000 connections 1 Destination Port = 23 Source Port = 23 Destination Port = 50,000PC-B PC-ASource port =50,001 Connection 2 Target port =23 Source port =23 Target port =50,001 Figure 8.2 Using port numbersAuthentication day label 8.048.4 Session EstablishmentWhen establishing a session to a remote peer, TCP and UDP use very different processes. As you may have guessed, the process used for UDP is very simple. When using UDP, both of the following scenarios indicate that a session has been established.