Chapter 14 Study Guide
Well-known Ports
0 to 1,023
Registered Ports
1,024 to 49,151
Which number or set of numbers represents a socket?
192.168.1.1:80
Do the below characteristics describe TCP, UDP or both?
3-way handshake - TCP Window size - TCP Connectionless - UDP Best for VoIP - UDP Port numbers - TCP / UDP Checksum - TCP / UDP Four exchanges to end session - UDP Sequence numbers - TCP / UDP Acknowledgments - TCP
Private and/or Dynamic Ports
49,152 to 65,535
Length
A 16-bit field that indicates the length of the UDP datagram header.
Checksum
A 16-bit field used for error checking of the datagram header and data.
Destination Port
A 16-bit field used to identify the destination application by port number.
Window size
A 16-bit field used to indicate the number of bytes that can be accepted at one time.
What is SACKs used for?
Alleviates congestion from retransmission of lost packets, by identifying and only resending missed information rather than all of the information
What is window size and how is it determined?
An advertisement of how much data the receive devices is willing to receive. It is determined via checksum
Which entities are involved in a temporary communication that is established by the transport layer?
Applications
What applications use UDP?
DNS, Streaming, Gaming, VOIP
What are ephemeral ports?
Dynamic / private ports
Do the below applications use TPC or UDP?
FTP - TCP TFTP - UDP SSH - TCP VoIP - UDP SNMP - UDP HTTP - TCP SMTP - TCP DNS - UDP DHCP - UDP Telnet - TCP
What does the transport layer add to a PDU?
Header / Trailer
How does UDP reassemble packets that is more than one datagram in length?
In the order that it was recieved
How does TCP reassemble packets that is more than one datagram in length?
In the original order
Why do we use multiplexing?
Increases efficiency of data transmission, therefore lowering costs
When using TCP what happens if part of the message is lost?
It is detected and then retransmitted
Which three fields are used in a UDP segment header?
Length Checksum Source Port
When using UDP what happens if part of the message is lost?
Nothing, the data is lost
What is the primary purpose of the transport layer?
Providing an end to end connection with as little errors as possible
What is it called when we combine the source IP address and source port number, or destination IP address and destination port number?
Sockets
Match the TCP flag to the correct step in the session establishment sequence.
Step 1 - SYN Step 2 - SYN + ACK Step 3 - ACK
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 are the ACK, SYN and FIN flags used in and for?
They are used in packet transmission and are used for tracing the route that IPs take
What are the advantages UDP has over TPC and vice versa?
UDP -has smaller packets, -is connectionless -and has more control TCP - has less corruption, - retransmission - and in order delivery
What are the characteristics of UDP and TCP?
UDP - Datagram oriented protocol Not 100% reliable basic error checking No sequencing of data Faster No retransmission 8 bytes fixed header length Lightweight Supports broadcasting DNS, DHCP, TFTP, SNMP, RIP, and VoIP.
What is an advantage of UDP over TCP?
UDP communication requires less overhead.
What are the three port groups, number range and description of the ports the transport layer uses?
Well known - 0 through 1023, controlled and assigned by IANA Registered - 1024 through 49151 - Not controlled by, but LOGGED by IANA Dynamic / private - 49152 through 65535 - IANA gives no information on these
Why would an application use UDP?
When an application requires lossless data transmission, or when transferring a large file
TCP connection-oriented protocol
is reliable provides extensive error checking sequencing of data slower retransmission 20-80 bytes header length Heavy weight Doesn't support broadcasting HTTP, HTTPs, FTP, SMTP and Telnet.
What are sequence numbers and acknowledgment numbers used for?
to enable ordered reliable data transfer for TCP streams.
