5. Fundamentals of TCP/ IP Transport and Applications

Which Functions does only TCP support?

-Error Recovery (Reliability) -Flow Control using windowing -Connection establishment and termination -Ordered data transfer and data segmentation

What are the parts of the URI?

-Test before :// identifies the protocol -Text between // and / identifies the server by name -Text after / identifies the web page

What is Connectionless protocol?

A protocol that does not require an exchange of messages and that does not require a pre-established correlation between two endpoints.

What is connection-oriented protocol?

A protocol that requires an exchange of messages before data transfer begins, or that has a required pre-established correlation between two endpoints

What is the key difference between TCP and UDP?

TCP provides a wide variety of services to applications, whereas UDP does not.

Draw diagram of 3 key fields used to identify the next header.

Before a receiving host can even examine the TCP or UDP header, and find the destination port field, it must first process the outer headers in the message. If the incoming message is an Ethernet frame, that encapsulates an IPv4 packet, the headers look like the details in Figure 5-15. The receiving host needs to look at multiple fields, one per header, to identify the next header or field in the received message. For instance, host A uses an Ethernet NIC to connect to the network, so the received message is an Ethernet frame. As first shown back in Figure 2-16 in Chapter 2, "Fundamentals of Ethernet LANs," the Ethernet Type field identifies the type of header that follows the Ethernet header— in this case, with a value of hex 0800, an IPv4 header. The IPv4 header has a similar field called the IP Protocol field. The IPv4 Protocol field has a standard list of values that identify the next header, with decimal 6 used for TCP and decimal 17 used for UDP. In this case, the value of 6 identifies the TCP header that follows the IPv4 header. Once the receiving host realizes a TCP header exists, it can process the destination port field to determine which local application process should receive the data.

UDP Port 68?

DHCP Client

UDP port 67?

DHCP Server

TCP/UDP port 53?

DNS

TCP port 21?

FTP Control

TCP port 20?

FTP Data

TCP Port 80?

HTTP

What is commonly used instead of URI?

In common speech, many people use the terms web address or the similar related term Universal Resource Locator (URL) instead of URI, but URI is indeed the correct formal term.

Which function do both UDP and TCP support?

Multiplexing Using Ports

What concept does Multiplexing rely?

Multiplexing relies on a concept called a socket. A socket consists of three things: An IP address A transport protocol A port number

TCP Port 110?

POP3

Which layer 4 protocol provides retransmission?

TCP provides retransmission (error recovery) and helps to avoid congestion (flow control), whereas UDP does not. As a result, many application protocols choose to use TCP.

TCP port 25?

SMTP

UDP Port 161?

SNMP

TCP port 22?

SSH

TCP port 443?

SSL

UDP Port 514?

Syslog

What is the purpose of TCP / UDP multiplexing?

TCP and UDP multiplexing tells the receiving computer to which application to give the received data. Each TCP and UDP segment uses a different Destination port number so the computer knows which application to give the data to. The server can tell which packets are sent from which of the 100 clients by looking at the source port of received TCP segments. The server can send data to the correct web client (browser) by sending data to that same port number listed as a destination port.

What is TCP Connection Establishment?

TCP connection establishment occurs before any of the other TCP features can begin their work. Connection establishment refers to the process of initializing Sequence and Acknowledgment fields and agreeing on the port numbers used.

How does TCP Implement Flow control?

TCP implements flow control by using a window concept that is applied to the amount of data that can be outstanding and awaiting acknowledgment at any one point in time. The window concept lets the receiving host tell the sender how much data it can receive right now, giving the receiving host a way to make the sending host slow down or speed up. The receiver can slide the window size up and down— called a sliding window or dynamic window— to change how much data the sending host can send.

How does TCP accomplish Reliability?

TCP numbers data bytes using the Sequence and Acknowledgment fields in the TCP header. TCP achieves reliability in both directions, using the Sequence Number field of one direction combined with the Acknowledgment field in the opposite direction.

How does TCP Accomplish all the functions it supports?

TCP, as defined in Request For Comments (RFC) 793, accomplishes the functions listed in Table 5-2 through mechanisms at the endpoint computers. TCP relies on IP for end-to-end delivery of the data, including routing issues. Regardless of whether two computers are on the same Ethernet, or are separated by the entire Internet, TCP performs its functions the same way.

TCP port 23?

Telnet

What is the message created by TCP called?

The message created by TCP that begins with the TCP header, followed by any application data, is called a TCP segment. Alternatively, the more generic term Layer 4 PDU, or L4PDU, can also be used.

What are the most important functions of OSI Transport Layer 4?

The most important functions this OSI layer are error recovery and flow conftrol.

What is the 3-way handshake?

This three-way connection establishment flow (also called a three-way handshake) must complete before data transfer can begin. The connection exists between the two sockets, although the TCP header has no single socket field. Of the three parts of a socket, the IP addresses are implied based on the source and destination IP addresses in the IP header. TCP is implied because a TCP header is in use, as specified by the protocol field value in the IP header. Therefore, the only parts of the socket that need to be encoded in the TCP header are the port numbers.

Define UDP?

UDP provides a service for applications to exchange messages. Unlike TCP, UDP is connectionless and provides no reliability, no windowing, no reordering of the received data, and no segmentation of large chunks of data into the right size for transmission.

Which Popular Applications do not need Error Recovery?

Voice over IP (VoIP) and video over IP, do not need error recovery, so they use UDP.

What is forward acknowledgment?

convention of acknowledging by listing the next expected byte, rather than the number of the last byte received

Which field of TCP header is used to set bits for SYN and ACK in the 3way handshare?

the Flag field is where the bits are set which either result in SYN or ACK

What is an example of URI?

www.cisco.com