Cisco Chapter 9: Transport Layer

Transport Layer Reliability

Two protocols provided: TCP and UDP. TCP supports reliability while UDP doesn't.

What is the complete range of TCP and UDP well-known ports?

0 to 1023

Which flag in the TCP header is used in response to a received FIN in order to terminate connectivity between two network devices?

ACK

Which two characteristics are associated with UDP sessions?

Destination devices receive traffic with minimal delay. Received data is unacknowledged.

What does a client do when it has UDP datagrams to send?

It just sends the datagrams.

Three operations that enable reliability with TCP

Numbering and tracking data segments transmitted to a specific host from a specific application Acknowledging received data Retransmitting any unacknowledged data after a certain period of time

Benefit of UDP

Perfect for applications that don't require reliability. Simple and Fast.

What is the role of the transport layer?

Responsible for establishing a temporary communication session between two applications and delivering data between them. Provides Connection-oriented data stream support, Reliability, Flow control, Multiplexing

Which three application layer protocols use TCP?

SMTP, FTP, HTTP

Which two flags in the TCP header are used in a TCP three-way handshake to establish connectivity between two network devices?

SYN ACK

Conversation Multiplexing

Segments data into small chunks. Label data chunks according to the conversation.

TCP

Supports packet delivery confirmation.

What applications are TCP useful for?

TCP is better for databases, web browsers, email clients, etc.

Transport Layer Responsibilities

Track individual conversations. Segment Data and Reassemble Segments. Identify the Applications.

What happens if the first packet of a TFTP transfer is lost

The TFTP application will retry the request if a reply is not received.

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 is a characteristic of a TCP server process?

There can be many ports open simultaneously on a server, one for each active server application.

What applications are UDP useful for?

UDP is better for live audio or video streaming, VoIP, etc.

What is a characteristic of UDP?

UDP reassembles the received datagrams in the order they were received.

Why does HTTP use TCP as the transport layer protocol?

because HTTP requires reliable delivery

What feature will allow different communication streams to occur at the same time, without having a single data stream using all available bandwidth?

multiplexing

What type of information is included in the transport header

destination and source port numbers

UDP

provides the basic functions for delivering data segments between the appropriate applications, with very little overhead and data checking. Data received is unacknowledged.

What kind of port must be requested from IANA in order to be used with a specific application?

registered port

What information is used by TCP to reassemble and reorder received segments?

sequence numbers

Which factor determines TCP window size?

the amount of data the destination can process at one time

What is a socket?

the combination of a source IP address and port number or a destination IP address and port number

During a TCP session, a destination device sends an acknowledgment number to the source device. What does the acknowledgment number represent?

the next byte that the destination expects to receive

When is UDP preferred to TCP?

when an application can tolerate some loss of data during transmission