CCNA1 (Chapter9)

to keep track of multiple conversations between devices Refer to curriculum topic: 9.1.2 The source port number in a segment header is used to keep track of multiple conversations between devices. It is also used to keep an open entry for the response from the server. The incorrect options are more related to flow control and guaranteed delivery.

TCP 3-way handshake Refer to curriculum topic: 9.2.1 TCP uses the 3-way handshake. UDP does not use this feature. The 3-way handshake ensures there is connectivity between the source and destination devices before transmission occurs.

1. client sends FIN 2. server sends ACK 3. server sends FIN 4. client sends ACK Refer to curriculum topic: 9.2.1 In order to terminate a TCP session, the client sends to the server a segment with the FIN flag set. The server acknowledges the client by sending a segment with the ACK flag set. The server sends a FIN to the client to terminate the server to client session. The client acknowledges the termination by sending a segment with the ACK flag set.

applications that are sensitive to delay Refer to curriculum topic: 9.2.3 UDP is not a connection-oriented protocol and does not provide retransmission, sequencing, or flow control mechanisms. It provides basic transport layer functions with a much lower overhead than TCP. Lower overhead makes UDP suitable for applications which are sensitive to delay.

to request that a source decrease the rate at which it transmits data Refer to curriculum topic: 9.2.2 The TCP sliding window allows a destination device to inform a source to slow down the rate of transmission. To do this, the destination device reduces the value contained in the window size field of the segment. It is acknowledgment numbers that are used to specify retransmission from a specific point forward. It is sequence numbers that are used to ensure segments arrive in order. Finally, it is a FIN control bit that is used to end a communication session.

1. meeting the reliability requirements of applications, if any 2. multiplexing multiple communication streams from many users or applications on the same network 3. identifying the applications and services on the client and server that should handle transmitted data Refer to curriculum topic: 9.1.1 The transport layer has several responsibilities. Some of the primary responsibilities include the following: - Tracking the individual communication streams between applications on the source and destination - Segmenting data at the source and reassembling the data at the destination Identifying the proper application for each communication stream through the use of port numbers - Multiplexing the communications of multiple users or applications over a single network - Managing the reliability requirements of applications

1. Length 2. Source Port 3. Checksum Refer to curriculum topic: 9.1.2 A UDP header consists of only the Source Port, Destination Port, Length, and Checksum fields. Sequence Number, Acknowledgment Number, and Window Size are TCP header fields.

The source decreases the amount of data that it transmits before it receives an acknowledgement from the destination. Refer to curriculum topic: 9.2.2 If the source determines that the TCP segments are either not being acknowledged or are not acknowledged in a timely manner, then it can reduce the number of bytes it sends before receiving an acknowledgment. This does not involve changing the window size in the segment header. The source does not decrease the window size that is sent in the segment header. The window size in the segment header is adjusted by the destination host when it is receiving data faster than it can process it, not when network congestion is encountered.

The client randomly selects a source port number. Refer to curriculum topic: 9.2.3 Because a session does not have to be established for UDP, the client selects a random source port to begin a connection. The random port number selected is inserted into the source port field of the UDP header.

192.168.1.1:80 Refer to curriculum topic: 9.1.2 A socket is defined by the combination of an IP address and a port number, and uniquely identifies a particular communication.

UDP communication requires less overhead. Refer to curriculum topic: 9.1.2 TCP is a more reliable protocol and uses sequence numbers to realign packets that arrive out of order at the destination. Both UDP and TCP use port numbers to identify applications. UDP has less overhead than TCP because the UDP header has fewer bytes and UDP does not confirm the receipt of packets.

1. DNS 2. VoIP Refer to curriculum topic: 9.2.4 Both DNS and VoIP use UDP to provide low overhead services within a network implementation.

transport Refer to curriculum topic: 9.1.1 The transport layer of the OSI model has several responsibilities. One of the primary responsibilities is to segment data into blocks that can be reassembled in proper sequence at the destination device.

the amount of data that can be sent before an acknowledgment is required Refer to curriculum topic: 9.2.2 The window size specifies the amount of data that can be sent before an acknowledgment is received from the receiver. This value specifies the highest number of bytes, not the required number of bytes.