Topic 10 Flashcards
What are the two roles of the Transport Layer?
Logical communications between applications running on different hosts
Link between the application layer and the lower layers
What are the five responsibilities of the Transport layer?
- Tracking individual conversations
- Segmenting data and reassembling segments
- Adding header information
- Identifying the applications
- Conversation multiplexing
What is the purpose of conversation multiplexing?
To interleave multiple conversations on the same network
What are the five TCP basic operations to provide reliability and flow control?
- Number and track data segments
- Sequence data
- Acknowledge received data
- Retransmit any unacknowledged data
- Send data at an efficient rate
Why is TCP a connection-oriented protocol?
Because it must establish a connection between the sender and the receiver
Why is UDP known as a best-effort protocol?
Because it does not provide reliability and flow control
Why is UDP a connectionless protocol?
Because it does not require an established connection
Why is UDP a stateless protocol?
Because it does not track information sent or received
Which layer 4 protocol is good for voice and DNS?
UDP
Why is TCP a stateful protocol?
Because it keeps track of the state of the communication session
What information in the transport layer header identifies the application?
Source and destination port numbers
Give four examples of applications that use TCP.
- HTTP
- FTP
- SMTP
- SSH
Give six examples of applications that use UDP.
- DHCP
- DNS
- SMMP
- TFTP
- VoIP
- Video Conferencing
Define the SOCKET and the socket pair.
- Socket: IP address + port number
- Socket pair: Source socket + destination socket
Write the socket pair for the diagram below.
Socket pair: 192.168.1.5:1099, 192.168.1.7:80
What are the three types of the port number groups?
- Well-known Ports
- Registered Ports
- Dynamic or Private ports
A message originates on PC1 and is destined for the web server. Fill in the following information: Source IP, Destination IP.
- Source IP: 192.168.1.10
- Destination IP: 192.168.0.254
Can ONE server have two or more services assigned to the same port number? Why?
No, because there is no way to differentiate between services
Explain the steps of the TCP connection establishment.
- Step 1: Client A requests a client-to-server session with the server
- Step 2: Server B acknowledges the request and requests a server-to-client communication session
- Step 3: Client A acknowledges the server-to-client communication session
How is the ordered delivery of segments achieved?
By assigning sequence numbers in the header of each segment
What is the purpose of flow control?
Adjusts the rate of data flow between source and destination
What information in the segment header is used by the flow control?
- Number of bytes
- Acknowledgment
Explain the window size concept.
Number of bytes that:
* The destination device can accept and process at one time
* Can be sent before an acknowledgment
* Modified by the destination at any time depending on the buffer availability
What does network congestion result in?
It results in packets being discarded
Compare and contrast UDP and TCP.
- TCP: Connection oriented, Stateful protocol, Reliable protocol, More overhead, Acknowledges data, Resends lost data, Delivers data in sequenced order, Tracks transmitted data segments, Better for databases, web browsers, email clients
- UDP: Connectionless, Stateless protocol, Non-reliable protocol, Low overhead, Does not require acknowledgment, Does not resend lost data, Delivers data as it arrives, Fast, Better for live audio or video streaming, VoIP
