Bits & Bytes: Week 3, I - Transport Layer Flashcards
Gathering data from multiple application processes of sender, enveloping that data with header and sending them as a whole to the intended receiver
Multiplexing
Delivering received segments at receiver side to the correct app layer processes
Demultiplexing
A 16-bit number that’s used to direct traffic to specific services running on a networked computer
a Port
What is the traditional HTTP port on a computer?
Port 80
A program running on a computer whose job is waiting to be asked for data
A server or service
What is the general term for the following:
10.1.1.100:80
A socket number or socket port
ACRONYM:
FTP
File Transfer Protocol
Which port is used to connect to an FTP server?
Port 21
What encapsulates an IP Datagram?
An ethernet frame
What encapsulates a TCP segment?
an IP datagram
What is the equivalent of an IP Datagram or Ethernet frame in the Transport Layer?
a TCP segment
What part of the TCP header contains the port number of the service the data is being sent to? How many bits?
The destination port field; 16 bits
What part of the TCP header is a high numbered port chosen from a special section of ports known as ephemeral ports? How many bits?
The source port field; 16 bits
When a web server replies, it is this part of the TCP header’s job to send the data to the correct program (for example, a browser instead of a wifi printer)
The source port field
This part of the TCP header is a number that keeps track of where in a sequence of TCP segments this segment is supposed to be. How many bits?
the Sequence number; 32 bits
This part of the TCP header is a number that represents the following segment to the current one.. How many bits?
the Acknowledgement number; 32 bits
How many bytes can be sent in an ethernet frame?
1518 bytes
What part of the data offset field of the TCP header communicates the length of the header so the receiving device knows when the data payload begins? How many bits?
the Header Length Field; 4 bits
What are the two parts of a TCP Segment?
The TCP Header and the data section
How many TCP control flags are there in a TCP segment?
There are 6; making up a 6 bit field
TCP protocol is very reliant on ________________ to make sure everything is being received
Acknowledgements
What part of the TCP segment contains the range of a sequence of numbers that might be sent before the receiver needs to return an acknowledgement? How many bits?
The window; 16 bits
What follows the window in a TCP segment?
The checksum
What is the checksum checking?
The checksum checks to make sure all of the data in a segment made it to the destination without data loss or corruption.
What 2 parts of the TCP segment are rarely, if ever, used? How many bits are they each?
the Urgent field and the Options field; 16 bits each
What is the field that immediately precedes the payload of a TCP segment?
The padding field
Which field of the TCP segment ensures that the data payload begins at the expected location?
The padding field
What is in the padding field?
a sequence of zeros
What field is mostly not used except for in very complicated control protocols?
The Urgent Field
How many TCP control flags are there?
6
A value of one (1) in this TCP Control flag area indicates that the segment is considered urgent
URGent
As a protocol, _____ establishes connections used to send long chains of segments of data. ______ and _____ just send individual packets of data.
TCP; IP; Ethernet
A value of one (1) in this TCP Control flag area indicates that the acknowledgement field should be examined
ACKnowledgement
this TCP Control flag area indicates that the transmitting device wants the receiving device to push currently buffered data to the application on the receiving end as soon as possible
PuSH
This TCP control flag area indicates that the data hasn’t been transmitted correctly and the data transfer for this TCP segment (or segments) needs to start over
ReSeT
this TCP Control flag area indicates that the receiving device needs to examine the sequence number field
SYNchronize
this TCP Control flag area indicates that all data has been transmitted and the connection can now be closed
FINish
When a connection is going to be closed, one device sends a FIN flag of which the other device signals receipt with an ACK flag, and then the other device sends its own FIN flag of which the first device signals receipt with an ACK flag. What is this process called?
the Four-way Handshake
When establishing a connection, a device sends a SYN flag to which a receiving device sends ACK/SYN flags in response. The originating device sends an ACK flag. This SYN, SYN/ACK, ACK exchange is known as…
the Three-way Handshake
In computer networking, a ________ is how two devices ensure they are speaking the same protocol and will be able to understand eachother
handshake
Upon receipt of a data segment over a TCP connection, what is always sent as a response?
A segment with an ACK flag
This is the instantiation of an endpoint in a potential TCP connection
a Socket
This is the actualization of something defined elsewhere; the creation of an instance of an abstraction
Instantiation
This TCP socket state means that a TCP socket is ready and waiting for incoming connections
LISTEN
This TCP socket state means that a synchronization request has been sent but the connection hasn’t been established yet
SYN_SENT
This TCP socket state means that a socket previously in a LISTEN state has received a synchronization request and sent a SYN/ACK flag back.
SYN_RECEIVED
This TCP socket state means that a TCP connection is in working order and both sides are free to send each other data
ESTABLISHED
This TCP socket state means that a FIN flag has been sent but a corresponding ACK has not been received yet
FIN_WAIT
This state means that the connection has been closed at the TCP layer but that the application that opened the socket hasn’t release its hold on the socket yet
CLOSE_WAIT
This TCP socket state means that the connection has been fully terminated and no further communication is possible.
CLOSED
LISTEN is a TCP socket state found on the client or server side?
Server side
SYN_RECEIVED is a TCP socket state found on the client or server side?
Server side
ESTABLISHED is a TCP socket state found on the client or server side?
Both client and server sides
FIN_WAIT is a TCP socket state found on the client or server side?
Both client and server sides
CLOSE_WAIT is a TCP socket state found on the client or server side?
Both client and server sides
CLOSED is a TCP socket state found on the client or server side?
Both client and server sides
SYN_SENT is a TCP socket state found on the client or server side?
Client side
This type of protocol establishes a connection and by its standards, ensures that all data has been properly transmitted
Connection-Oriented Protocol
Is TCP a connection-oriented or connectionless protocol?
TCP is a connection- oriented protocol
How does TCP ensure that data that has been resent due to errors at lower levels is able to be assembled in the correct order?
Sequence Numbers
Is UDP a connection-oriented or connectionless protocol?
UDP is a connectionless protocol
This type of transfer protocol simply sends a packet of data without creating a connection with a stream of acknowledgements
Connectionless Protocol
This protocol is more reliable but can require a lot of bandwidth; this protocol is less reliable but can send higher quality data packets because it requires less bandwidth
TCP (connection-oriented); UDP (connectionless)
What is an example of data transfer using UDP?
Streaming video
How many bits are used to represent a port?
16 bits
What is the range of numbers that can be assigned to ports?
0-65535
What port number isn’t used for network traffic but can be used for communication between different programs on the same device?
Port 0
What is the range of numbers used to represent system ports?
1-1023
What is another term for system ports?
Well-known ports
What is the range of numbers used to represent registered ports?
1024-49151
What is the range of numbers used to represent ephemeral ports?
49152-65535
What is another term for ephemeral ports?
Private Ports
This kind of port is considered the official port for most well-known network services.
System, or Well-known, Ports
This kind of port is used for less common network services
Registered Ports
This kind of port is unregistered, generally used for establishing outbound connections, and assigned to the client for just one connection
Ephemeral, or private, ports
This is the primary way to stop unwanted traffic from entering a network
Firewalls
In which TCP/IP model layer is a firewall most often used?
The transportation layer
At the transportation layer, _______ are configured to block traffic to certain ports while allowing traffic to other ports
Firewalls
Firewalls block ranges of IP addresses at the __________ layer,
Network