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CCNA- OSI Transport Layer
Chapter 4
76
Computer Networking
Undergraduate 1
09/05/2012

Additional Computer Networking Flashcards


 

 


 

Cards

Term
What are the 4 primary responsibilites of the Transport Layer?
Definition
  1. Tracking communication between applications on source/destination hosts.
  2. Segmenting and managing data.
  3. Reassembling the segments.
  4. Identifying the different applications.
Term

What does the Transport Layer header provide?

 

Definition

It identifies the segment of data and provides for identification of the Transport Layer Protocol to use.

 

Term

Describe the process of segmentation and reassembly?

 

Definition

The process divides application data into blocks of data that are an appropriate size, then reassembles the data before sending it to the destination application or service.

 

Term

How does the Transport Layer accomplish conversation multiplexing?

 

Definition

Each of these applications or services is assigned an address known as a port so that the Transport layer can determine with which application or service the data is identified.

 

Term

What are the four additional duties the Transport Layer can provide?

 

Definition

Connection-oriented conversations

  •  Reliable delivery
  •  Ordered data reconstruction
  •  Flow control

 

Term

What are the four processes that the Transport Layer uses to control conversations?

 

Definition

 Establishing a Session

  •  Reliable Delivery
  •  Same Order Delivery
  •  Flow Control

 

Term

What does reliability mean to a network?

 

Definition

Ensuring that each piece of data that the source sends arrives at the destination.

 

Term

What are the three basic operations of reliability at the transport layer?

 

Definition

 tracking transmitted data

  •  acknowledging received data
  •  retransmitting any unacknowledged data

 

Term

What trade-off is necessary to ensure reliability?

 

Definition

The value of reliability and the burden it places on the network.

 

Term

How is a best-effort protocol different than a reliable protocol?

 

Definition

There is no acknowledgement that the data is received at the destination.

 

Term

What is another term used to describe a best-effort protocol?

 

Definition

Unreliable

 

Term

List some examples of applications that require reliable transmission.

 

Definition

Databases, web pages, and e-mail

 

Term

Give an example of an application that can use unreliable transmission.

 

Definition

Streaming video

 

Term

What are the two most common protocols at the Transport Layer?

 

Definition

Transmission Control Protocol (TCP) and 

User Datagram Protocol (UDP)

 

Term

What is the advantage of using UDP?

 

Definition

Speed

 

Term

What are the pieces of UDP information called?

 

Definition

Datagram

 

Term

What are some applications that use UDP?

 

Definition

Applications that use UDP include:

Domain Name System (DNS)

Video Streaming

Voice over IP (VoIP)

 

Term

What are the 3 additional functions that TCP offers?

 

Definition

Same order delivery, reliable delivery, and flow control.

 

Term

How much overhead is required to offer the 3 functions of TCP?

 

Definition

20 bytes

 

Term

What are the pieces of TCP information called?

 

Definition

Segments

 

Term

What are some applications that use TCP?

 

Definition

Applications that use TCP are:

Web Browsers

E-mail 

File Transfers

 

Term

What are the unique identifiers that define the conversations called?

 

Definition

Port numbers

 

Term

In the originating message what is the source port?

 

Definition

The number for this communication associated with the originating application on the local host.

 

Term

In the originating message what is the destination port?

 

Definition

The number for this communication associated with the destination application on the remote host.

 

Term

How do server processes have port numbers assigned?

 

Definition

Statically

 

Term

How do clients have port numbers assigned?

 

Definition

Dynamically

 

Term

What is another term sometimes used instead of port number?

 

Definition

Socket number

 

Term

For this course, what does a socket pair describe?

 

Definition

The source and destination IP addresses and port numbers, is also unique and identifies the conversation between the two hosts.

 

Term

What organization is responsible for assigning port numbers?

 

Definition

IANA Internet Assigned Numbers Authority

 

Term

What is the range of Well Known Ports?

 

What are well known ports?

 

Definition

0 to 1023


 

The ports reserved for services and applications.

 

Term

What is the range of Registered Ports?


 

What are registered ports?

 

Definition
Term

What is the range for Dynamic or Private Ports?

 

What are dynamic or private ports?

 

Definition

49152 to 65535


 

Also known as Ephemeral Ports, these are usually assigned dynamically to client applications when initiating a connection. It is not very common for a client to connect to a service using a Dynamic or Private Port (although some peer-to-peer file sharing programs do).


 

Term

Is it possible for a port number to be used by both TCP and UDP?

 

Definition

yes

 

Term

What is the utility that can be used to view open connections?

 

Definition

Netstat

 

Term

What are the two reasons data is divided into pieces before it is sent?

 

Definition

This ensures that data is transmitted within the limits of the media, and that data from different applications can be multiplexed on to the media.

 

Term

 

What is provided in a UDP header?



 

Definition

 

Port Numbers

 

Term

What is provided in a TCP header?

 

 

Definition

Port, sequence, acknowledgement, and flow control numbers

 

Term

In which protocol do segments arrive in an unspecified order?

 

Definition

UDP

 

Term

What makes TCP a reliable protocol?

 

Definition

Connection-oriented sessions

 

Term

What do acknowledgements do?

 

Definition

Let the sender know you received the data

 

Term

What happens if the acknowledgment does not arrive in the predetermined time?

 

Definition

It retransmits that data to the destination.

 

Term

What is the additional overhead created in the hosts by using TCP?

 

Definition

The necessity to keep track of which segments are awaiting acknowledgement and by the retransmission process.

 

Term

Which device initiates the communication process?

 

Definition

Client

 

Term

 

What can never happen in two server conversations?

 

Definition

 

Two services assigned to the same port number within the same Transport layer services.

 

Term

What are the three steps in TCP connection establishment?

 

Definition

  1. Client sends server a SYN request to synchronize sequence numbers. (Currently 0)
  2. Server confirms by returning an ACK flag (the sequence number plus one).
  3. Client sends ACK flag, connectiom is established.

 

Term

 

What are the six control bit fields possible and what do they mean?

 

Definition

 

URG - Urgent pointer field significant

ACK - Acknowledgement field significant

PSH - Push function

RST - Reset the connection

SYN - Synchronize sequence numbers

FIN- No more data from sender

 

Term

What is the Initial Sequence Number (ISN)?

 

Definition

The initial value for the sequence number is randomly chosen and is used to begin tracking the flow of data from the client to the server for this session

 

Term

What is sent back to the client in step 2?

Definition

the server sends a segment back to the client with the ACK flag set indicating that the Acknowledgment number is significant

 

Term

What is the value of the acknowledgment number field?

Definition

Equal to the client initial sequence number plus 1

Term

Explain what is meant by 2 one-way sessions exist in TCP?

Definition

One from the client to the server, and the other from the server to the client

Term

What is the final step in the three-way hand shake?

Definition

The client responds with both the sequence and acknowledgement bit set and no data.

Term

What are 3 ways in which security can be added?

Definition

  •  Denying the establishment of TCP sessions
  •  Only allowing sessions to be established for specific services
  •  Only allowing traffic as a part of already established session

 

Term

What must be sent to close a TCP session?

Definition

FIN finish control flag

Term

What are the 4 exchanges needed to close a TCP conversation?

Definition

1. 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 an ACK to acknowledge the FIN from the server.

Term

How does TCP reassemble packets into the original data file?

Definition

Sequence numbers are assigned in the header of each packet to achieve this goal

Term

How are sequence numbers incremented?

Definition

The sequence number is incremented by the number of bytes that have been transmitted.

Term

What does the receiving process do with the TCP segment?

Definition

The receiving TCP process places the data from a segment into a receiving buffer.

Term

Where do the reassemble segments go?

Definition

To the Application Layer

Term

What happens when all the segments do not arrive?

Definition

Any segments that arrive with noncontiguous sequence numbers are held for later processing.

Term

What is the relationship between sequence and acknowledgement numbers work?

Definition

The sequence number indicates the relative number of bytes that have been transmitted in this session including the bytes in the current segment. TCP uses the acknowledgement number in segments sent back to the source to indicate the next byte in this session that the receiver expects to receive

Term

What is the process TCP uses with sequence and acknowledgement numbers called?

Definition

Expectational acknowledgement

Term

What does TCP do to overcome the overhead of waiting for acknowledgements?

Definition

Multiple segments of data can be sent before and acknowledged with a single TCP message in the opposite direction.

Term

What is the name for the amount of data that can be sent before an acknowledgement is received called?

Definition

Window size

Term

How does TCP handle missing segments?

Definition

When TCP at the source host has not received an acknowledgement after a predetermined amount of time, it will go back to the last acknowledgement number that it received and retransmit data from that point forward.

Term

What do hosts implement today to improve the TCP process?

Definition

If both hosts support Selective Acknowledgements, it is possible for the destination to acknowledge bytes in discontinuous segments and the host would only need to retransmit the missing data.

Term

How does flow control assist the reliability of TCP transmissions?

Definition

By adjusting the effective rate of data flow between the two services in the session. When the source is informed that the specified amount of data in the segments is received, it can continue sending more data for this session.

 

 

Term

What does window size specify?

Definition

The amount of data that can be transmitted before an acknowledgement must be received.

Term

How does TCP use window size to improve communication?

Definition

TCP feedback mechanism adjusts the effective rate of data transmission to the maximum flow that the network and destination device can support without loss. TCP attempts to manage the rate of transmission so that all data will be received and retransmissions will be minimized.

Term

What happens to window size when network resources are constrained?

Definition

TCP can reduce the window size to require that received segments be acknowledged more frequently

Term

What happens after periods of transmission with no data losses or constrained resources?

Definition

The receiver will begin to increase the window field.

Term

What do you think occurs with window size on the school network when a major update occurs district wide? (smaller, larger)

Definition

The window size would get smaller

Term

According to the first 2 paragraphs, what is the major advantage of using UDP?

Definition

Lower overhead

Term

What are the key Application layer protocols that use UDP includes?

Definition

Domain Name System (DNS)

Simple Network Management Protocol (SNMP)

Dynamic Host Configuration Protocol (DHCP)

Routing Information Protocol (RIP)

Trivial File Transfer Protocol (TFTP)

Online games

Term

What is UDP also referred to as?

 

Definition

Transaction based

Term

How are TCP and UDP similar?

Definition

They both use port numbers

Term

 

What happens to port numbers in a response from the server?

Definition

The source and destination port numbers in the datagram header are reversed.

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