Module 14: Transport Layer
What is the complete range of TCP and UDP well-known ports?
0 to 1023
Assume a host with IP address 10.1.1.10 wants to request web services from a server at 10.1.1.254. What would be the correct socket pair?
10.1.1.10:1099, 10.1.1.254:80
What is the complete range of TCP and UDP Registered ports?
1024 to 49151
What is the complete range of TCP and UDP dynamic ports?
49152 to 65535
three-way handshake
A three-step process in which Transport layer protocols establish a connection between nodes. The three steps are: Node A issues a SYN packet to node B, node B responds with SYN-ACK, and node A responds with ACK.
Selective Acknowledgement (SACK)
Allows a receiver to acknowledge non-consecutive data, so that the sender can retransmit only what is missing at receivers end.
What are the transport layer responsibilities?
Conversation Multiplexing segmenting data and reassembling segments tracking individual conversations
Which two fields are the same in a TCP and UDP header?
Destination port number Source port number
How does a networked server manage requests from multiple clients for different services?
Each request has a combination of source and destination port numbers, coming from a unique IP address.
conversation multiplexing
Enables multiple applications to communicate over the network at the same time on a single device
what applications would use the TCP transport layer protocol?
HTTP and FTP
Control bits (6 bits)
Includes bit codes, or flags, that indicate the purpose and function of the TCP segment.
Which TCP header statement is true?
It consists of 10 fields in a 20 byte header
Which UDP header statement is true?
It consists of 4 fields in an 8-byte header
Why is UDP desirable for protocols that make a simple request and reply transactions?
Low Overhead
Which control bit flags are used during the three-way handshake?
SYN and ACK
What field is used by the destination host to reassemble segments into the original order?
Sequence number
Which of the following would be valid source and destination ports for a host connecting to an email server?
Source: 49152, Destination: 25
Which of the following would be valid source and destination ports for a host connecting to a DNS server?
Source: 49152, Destination: 53
Which transport layer protocol ensures reliable same-order delivery?
TCP
Which transport layer feature is used to establish a connection-oriented session?
TCP 3-way handshake
Which two applications would use the UDP transport layer protocol?
TFTP and VoIP
What is flow control?
The amount of data that the destination can receive and process reliably
Maximum Segment Size (MSS)
The maximum amount of data that the destination device can receive.
What happens if part of an FTP message is not delivered to the destination?
The part of the FTP message that was lost is re-sent
What happens when a sending host senses there is congestion?
The sending host reduces the number of bytes it sends before receiving an acknowledgement from the destination host.
Which layer is responsible for establishing a temporary communication session between the source and destination host applications?
Transport Layer
Which of the following is a stateless best-effort delivery transport layer protocol?
UDP
DHCP Port Number
UDP 67, 68
Which transport layer protocol statement is true?
UDP is a best-effort delivery protocol
Which UDP datagram reassembly statement is true?
UDP reassembles the data in the order that it was received
DNS port number
UDP/TCP 53
Checksum field
Used for error checking of datagram header and data
Which transport layer protocol would be used for VoIP applications?
User Datagram Protocol (UDP)
Which two operations are provided by TCP but not by UDP?
acknowledging received data retransmitting any unacknowledged data
What type of applications are best suited for using UDP?
applications that are sensitive to delay
How many exchanges are needed to end both sessions between two hosts?
four exchanges
Which Windows command would display the protocols in use, the local address and port numbers, the foreign address and port numbers, and the connection state?
netstat
What TCP mechanism is used to enhance performance by allowing a device to continuously send a steady stream of segments as long as the device is also receiving necessary acknowledgements?
sliding window
Which action is performed by a client when establishing communication with a server via the use of UDP at the transport layer?
the client randomly selects a source port number
What is a socket?
the combination of a source IP address and port number or a destination IP address and port number
What is the purpose of using a source port number in a TCP communication?
to keep track of multiple conversations between devices
What is a responsibility of transport layer protocols?
tracking individual conversations
Which port group includes port numbers for FTP, HTTP, and TFTP applications?
well-known ports
What field is used to provide flow control?
window size
