week 10 Flashcards
what is the role of the transport layer
–> it is the link between the application layers and the lower layers that are responsible for network transmission
–> The transport layer is responsible for establishing a temporary communication session between 2 applications and delivering data between them.
what are the 2 protocols the transport layer uses to deliver data between applications
- -> transmission control protocol (TCP)
- -> User datagram protocol (UDP)
what are the primary responsibilities of the transport layer protocols
–> tracking the individual communications between applications on the source and destination hosts
–> segmenting data for manageability and reassembling segmented data into streams of application data at the destination
–> identifying the proper application for each communication stream
the transport layer is the link between the application layer and the which is responsible for _____________
network transmission
what is conversation multiplexing
- -> the transport layer divides the data into segments that are easier to manage and transport
- -> multiple applications can use the network at the same time
why is the data in the transport layer broken into segments
- -> easier to manage and transport
- -> allows for conversation multiplexing
- -> facilitates data transport by the lower network layers
- -> error checking can be performed on the data in the segment to check if the segment is changed during transmission
- -> the transport layer also ensures that with multiple applications running on a device, all applications receive the correct device
characteristics of transmission control protocol (TCP)
- -> provides reliable delivery by retransmitting lost of corrupt data
- -> makes larger demands on the network (more overhead)
- -> connection oriented protocol - creates a session between source and destination
- -> it is a stateful protocol as it tracks the session
- -> provides for flow control as it regulates the amount of data transmitted
- -> ordered data reconstruction which reconstructs ordering and sequencing of segments
- -> uses acknowledged delivery and other processes to ensure delivery
characteristics of UDP
- -> provides teh basic functions for delivery
- -> connectionless
- -> unreliable data
- -> no ordered data reconstruction
- -> no flow control
- -> stateless protocol
- -> less overhead
how do application developers choose between TCP and UDP?
–> since there is a trade-off between reliability and the burden it places on the network, developers choose based on the requirements of their application
what are the required properties for streaming video / ip telephony
- -> fast
- -> low overhead
- -> does not require acknowledgements
- -> does not resend lost data
- -> delivers data as it arrives
what are the required protocol properties for smtp/pop or http
- -> reliable
- -> acknowledge data
- -> resends lost data
- -> delivers data in order sent
what do tcp and udp use to differentiate between applications
port numbers
what is a socket
–> a combination of source and destination ip addresses and source and destination port numbers is called socket
–> used to identify the server and service which is requested by the client
what is a socket pair
- -> consists of source and destination ip addresses and port numbers
- -> it is unique and identifies the specific conversation between 2 hosts
_________ assigns the port numbers
internet assigned numbers authority
what are the 3 types of ports
- -> well known ports
- -> registered ports
- -> dynamic / private ports
what is a well known port
- -> ports with numbers (0 to 1023)
- -> reserved for commonly used services and applications
- -> eg are HTTP, SMTP, TELNET
what are registered port numbers
- -> numbers are from 1024 to 49151
- -> assigned to user processes or applications
- -> primarily individual applications user has chosen to install
what are dynamic / private ports
- -> numbers from 49152 to 65535
- -> assigned dynamically to client applications when a client initiates connection to a service
what is the TCP 3 way handshake
- -> the initiating client requests a client to server communication session with the server (SYN)
- -> the server acknowledges the client server communication session and requests a server to client communication session (SYN ACK)
- -> the initiating client acknowledges the server to client communication session (ACK)
what are the fields that contain control information within TCP segment header
ACK => acknowledgement field significant
RST => reset the connection
SYN => synchronize sequence numbers
FIN => No more data from the sender
what are the steps in TCP session termination
–> when the client has no more data to send in the stream, it sends a segment with the FIN flag set
–> the server sends an ACK to acknowledge the receipt of the FIN to terminate the session from client to server
–> the server sends a FIN to the client, to terminate the server to client session
–> the client responds with ACK to acknowledge the FIN from the server
why are segments resequenced in tcp
- -> segments may arrive at their destination out of order
- -> the data in these segments are reassembled into the original order using sequence numbers
___________ and ____________ are used to confirm the receipt
acknowledgment(ACK) and sequence number(SEQ)
what is exceptional acknowledgment
TCP uses the ACK number sent back to the source to indicate the next byte that the receiver expects to receive
what is the window size
amount of data that a source can transmit before an acknowledgment must be received
how does TCP provide flow control
–> it does this by adjusting the rate of data flow between source and destination of a given session
how does TCP decide the amount of data segments in bytes that the destination device can accept
it does this by using window size field in TCP header during 3 way handshake
what does TCP do in case of limited buffer memory
it sends a smaller window size value to the source as part of an acknowledgment to reduce window size
how does tcp handle segment loss
when source host does not receive an acknowledgment after a predetermined amount of time, it retransmits segments from the last ACK number received
what types of applications should use UDP
- -> tolerate small loss of data
- -> cannot tolerate delay
UDP is a simple protocol that provides _____________-
basic transport layer function
what protocols use TCP
Telnet ftp http smtp dns
what protocols use UDP
DNS TFTP VoIP IPTV DHCP
