ISA 301 Lecture 3 - Transport and Application Layer Services

Terminal Network

(aka Telnet) is an application layer program that enables a user to remotely login and use the resources of a remote computer. -requires authentication -designed for use in time-sharing environments In-depth explanation: To be successful, the remote computer must authenticate the user. Telnet was designed for use in time-sharing environments. Network administrators also use Telnet to monitor, configure, and maintain remote devices.

IPv6 packets have three potential components:

-A required header -An optional extension header -The message or payload With IPv6, congestion controlled and non-congestion controlled traffic can be identified. IPv4 did not have this built-in capability. IPv6 allows the network administrator to fine-tune the delivery of data packets so that what is important gets through first.

Well-known port

A well-known port on the Internet is as an address number, specifically a port address, which is standardized or bound to a particular well-known service. The advantage to the user is that he or she does not need to specify such a port address when accessing a well-known service.

Question 4 True or False: TCP and UDP use "port numbers," included in every TCP and UDP header, to identify specific processes and services running on the receiver's host device.

Answer: TRUE

Review Question 2 TCP takes a three-step approach to establishing a reliable communication. First, from the transport layer of the sending device a request packet is transmitted to the receiving device's transport layer asking if a session can be established. Second, if available, the receiving device sends a packet back to the sending device indicating that it is available for communication. What is the third step? A) the session disconnects upon being established B) the sending device begins to send its data to the receiving device C) the packet disappears upon connection D) the packet transports to the session

B) the sending device begins to send its data to the receiving device

Well-known service

Like a well-known port, a well-known service on the Internet is a standardized Internet program that is associated with a well-known port address.

Simple Mail Transfer Protocol (SMTP)

a popular network protocol for providing e-mail services. -makes use of two components: a user agent and a mail transfer agent.

What are the two types of IPv6 addressing techniques that can embed IPv4 addresses defined by IETF (Internet Engineering Task Force)

compatible and mapped -Compatible and mapped addresses travel through networks of the opposing sorts. Both will be required as we transition from IPv4 to IPv6.

Tunneling

-Automatic -Configured is recommended when two IPv6 devices want to communicate and yet must pass through an IPv4 network. For automatic tunneling, the receiving device already uses a compatible IPv6 address, so no reconfiguration is required.

What are the two key transport layer protocols

-Transmission Control Protocol (TCP) -User Datagram Protocol (UDP) They operate in very different ways.

Looking at the top two TCP/IP layers, in context:

-it is notable that the application layer provides the enterprise network user an interface for connecting to and interacting with the network. -When two hosts in a TCP/IP network communicate, it is critical, as with any communication, that they be able to identify each other. In this communication, the transport layer manages the transmission of data between sender and receiver.

What is the three step approach that TCP uses to establish a reliable communication?

1. From the transport layer of the sending device, a request packet is transmitted to the receiving device's transport layer asking if a session can be established. 2. If available, the receiving device sends a packet back to the sending device indicating that it is available for communication. 3. The sending device begins to send its data to the receiving device. A checksum value that is used by the receiver to determine whether a transmission error has occurred. TCP uses the sliding windows method of flow control.

IPv4 Address Notation

32-bit, or 4 byte value A notable feature of an IPv4 address is that it is limited to a 32-bit, or 4 byte, value. The binary equivalent of an IPv4 address is often expressed in a dotted-decimal format, for example, 192.37.113.12.

Loopback address

A device uses the loopback address to test itself to determine whether it has been properly configured for communication, without going out into the network. In effect, the device uses the loopback address to make sure that its software layers have been correctly set up to allow for communications.

Review Question 3 Which two technologies were NOT included in IPv4? A) encryption and authentication B) addressing and regenerating C) specifying and punctuating D) resolving and reconciling

A) encryption and authentication

Learning Objectives

After studying this chapter, you should be able to: • Differentiate between transport and application layer services. • Describe the key elements of transport services. • Differentiate between connection-oriented and connectionless communications. • Describe the key elements of application layer services. • Define a well-known port. • Define a well-known service. • Identify ways of transitioning from IPv4 to IPv6. • Describe IPv6 addressing types and packet format.

Transport Layer

As with network layer services, the transport layer, which sits above the network layer and below the application layer, also uses protocols.

What does connectionless/unreliable mean

Connectionless means that the sender does not have to first establish a link to the receiver before beginning to transmit data. Unreliable does not mean worse or unacceptable. With UDP, unreliable simply means that the sender does not guarantee to the receiver that all of the transmitted data packets will arrive.

What three main components did Mockapetris' suggest?

First, a hierarchical name space that divided the host system database into components called "domains." Second, domain name servers would provide information about host and subdomains within a domain. And finally third, that resolvers would generate requests for information from configured domain name servers. The original DNS name space assigned seven top-level domains:

Port numbers

IP addresses are necessary for a sender and receiver to be able to communicate with each other. TCP and UDP use "port numbers," included in every TCP and UDP header, to identify specific processes and services running on the receiver's host device.

IPv6 Address Notation

IPv6 uses 128 bits, or 16 bytes. Here is an example of what could be an IPv6 address: DA3F:38C7:1934:EC8B:5671:0000:A690:21FD In the IPv6 addressing scheme, each 128-bit address string uniquely identifies one single networked device on the worldwide Internet. With IPv6 there is much greater flexibility in assigning of network and host portions within the 128-bit string. Another difference that IPv6 makes in its addressing scheme is that only three address types are allowed: unicast, multicast, and anycast

SMTP: user agent (UA)

On the client end, the user agent (UA) prepares the message and puts it into a form that can be transmitted across a TCP/IP network.

When can UDP be a better choice than TCP

Speed. Depending on the data being transmitted, UDP can be the better choice than TCP. Because UDP does not require the sender and receiver to establish a connection before sending data, time is saved, increasing efficiency. Figure 7.2 demonstrates a UDP transmission. -The use of UDP has evolved over time. Although still mostly associated with small data files that require few packets, today UDP also is used for streaming audio and video.

Difference between TCP and UDP

TCP has much more overhead than its counterpart, UDP. For a message for which it is especially important that all the data packets arrive without loss and in the proper sequence, TCP is the delivery method of choice. For noncritical data or for data that can fit within a single packet, UDP is the more appropriate protocol.

Ethical Perspective of the exchange of technical information/sharing

The issue of sharing has become a major ethical issue. Web-based applications, primarily using peer-to-peer sharing protocols, enable a user to exchange and share files with other local computers. Many of these "shared" files are music, video, or other types of artistic- or entertainment-based materials. Many users who "share" these works do not reimburse the artist or owner for use of the work.

Chapter Summary part 1

The two key transport layer protocols are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP). Port-numbers are assigned by the Internet Assigned Numbers Authority (IANA). Each TCP/IP based system will have a "Services" file that holds a list or inventory of the most common well-known port numbers and the well-known services these port numbers are assigned to. TCP has much more overhead than its counterpart, UDP. TCP provides for packet acknowledgment, error detection and control, and flow control. Generally, the use of TCP as a delivery service is appropriate when larger data streams that cannot fit into a single packet need to be transmitted across the network. TCP takes a three-step approach to establishing a reliable communication.

Internet Corporation for Assigned Names and Numbers (ICANN)

These port-numbers are assigned by the Internet Corporation for Assigned Names and Numbers (IANA).

User Diagram Protocol (UDP)

Unlike TCP, User Datagram Protocol (UDP) is a connectionless, unreliable delivery service.

Chapter summary part 2

Unlike TCP, User Datagram Protocol (UDP) is a connectionless, unreliable delivery service. The application layer sits at the top of the TCP/IP layer stack, directly above the transport layer. The application layer provides the user an interface and a connection to the network. Many application layer protocols follow the client/server approach. In the client/server model, a local host machine runs an application layer program called a client. The client application requests a resource from a remote host that is running a server-based application layer program. Common application layer services include, but are not limited to, Telnet, FTP, SMTP, SNMP, HTTP, and DNS. Gradually replacing IPv4 is the new and improved Internet, IPv6 (Internet Protocol version 6), also known as IPng (Internetworking Protocol, next generation).

Anycast address

Unlike a multicast address, the anycast address is for a group of devices that are of the same type prefix. The anycast address is new to IPv6.

There are a number of protocols associated with the Application layer, as illustrated in Figure 7.5

When users connect to the Internet, they enter a Domain Name System (DNS) server or URL (Uniform Resource Locator) into their Web browser or other application to resolve the name of the system provided into an IP address. -Most of us find entering a user-friendly DNS/URL name, such as www.pearson.com, easier to work with than a numeric IP address. -The Internet's Domain Name System is often compared to a hierarchical directory tree as illustrated in Figure 7.6.

Unicast adress

defines one specific networked, or host, device. No two devices can use the same unicast address, with two exceptions: the unspecified address and the loopback address.

What is another popular application layer program?

file transfer protocol (FTP)

Transmission Control Protocol (TCP)

is a connection-oriented protocol; it is also called a reliable stream transport layer service. The term connection oriented applies because the sender cannot send until the receiver is contacted and agrees to a communication.

Simple Network Management Protocol (SNMP)

provides a basic set of tools for managing a TCP/IP network. -uses UDP, so it is connectionless -Manager and agent -MIP Extended explanation: Many networked devices, including routers, switches, and hubs, can serve as agents, reporting back to the manager device regarding the status of the network. Each agent has a Management Information Base (MIB) that it builds as it collects network statistics. Based on the data received, a management station can cause an action to take place at an agent or it can change an agent's configuration setting.

Socket

the combination of an IP address and a port-number -Sockets are notated by the IP address anchored at the end with a colon and the port number, for example, 157.34.80.102:53. In this instance, the well-known port number 53 is associated with a Domain Name Service (DNS).

SMTP: mail transfer agent (MTA)

transfers the mail across the network or over the Internet.

Management Information Base (MIB)

used primarily to access information on the World Wide Web (WWW). -enables data (text, hypertext, video, graphic, audio, or other medium) to be transferred from a server device to client, meaning a Web server to a client browser. -There are a number of protocols associated with the Application layer, as illustrated in Figure 7.5

File Transfer Protocol (FTP)

used to copy files from one host to another. - Depending on the connection, user authentication might be required. -Figure 7.3 provides examples of data required from a typical FTP client.

Multicast address

used when a message needs to be sent to a group of devices that may or may not be on the same "type prefix."

Explain transition from IPv4 to IPv6 -name the three approaches to assist in the transition to the new internet

•A decade of transition •Guidelines -Dual stack -Tunneling -Header translation The full transition from IPv4 to IPv6 will not happen over one or two years, and will more likely be a decade in the doing. The IPv6 design team has put together a set of guidelines to assist in the transition to the new Internet. Their recommendations take three approaches: dual stack, tunneling, and header translation.

Why is IPv4 being retired and how does IPv6 differ?: IPv4 limitations

•Data: text, numbers, video, audio, graphics, voice •Two-level and hierarchical addressing scheme •Classes: A, B, C, D, E •Multimedia types of data •Encryption and authentication •Wireless revolution •Workarounds IPv4 can be used to carry multimedia types of data, such as video and audio, but not very well. When the Internet was initially designed, primarily as a tool for researchers, the types of data were fairly simple: textual and numerical. Today, we require the IPv4 infrastructure to transmit much more complex types of data, including video, audio, graphics, and voice. IPv4 can do this, but not as efficiently as is desired or required in today's world of instant mass communications. The very popularity of IPv4 has also resulted in the rapid deletion of an essential element needed of any entity that wants an Internet presence, namely an IP address. What is stalling this multi-billion dollar wireless revolution in its tracks, however, is the lack of IPv4 addressing. Wireless devices and the wireless LANs they run on must have IP addressing availability in order to fulfill their promise. Without an IP address, there is no connectivity. Workarounds using techniques such as Network Address Translation (NAT), subnetting, and supernetting have helped extend IP addresses, but such techniques can only take IPv4 so far. Many believe this limit has been reached. In response, the Internet engineering community began in the early 1990s to develop a solution. That solution is IPv6.

The Domain Name System, or DNS

•Peter Mockapetris •To allow ordinary users of the Internet a way of accessing remote resources without the need for knowing the numeric IP address of the resource •Name servers was initially put forward in 1983 by Peter Mockapetris as two IETF (Internet Engineering Task Force) documents. A key intent was to put in place a means for allowing ordinary users of the Internet a way of accessing remote resources without the need for knowing the numeric IP address of the resource. DNS allows users to instead supply character based "user-friendly" names, such as www.pearson.com. These user-friendly names would then be resolved or equated, to the true IP address of the resource.

IPv6 and the New Internet

•Retiring IPv4 •All good things must come to an end •Ipng The Internet has had an evolutionary plan in place. IPv4 has been around since the late 1960s and has lasted due to its design, reliability and flexibility. But, "all good things must come to an end." Gradually replacing IPv4 is the new and improved Internet, IPv6 (Internet Protocol version 6), also known as IPng (Internetworking Protocol, next generation).

Application Layer Services

•Sits at the top of the TCP/IP layer stack •Provides the user an interface and a connection to the network •Follow client/server approach Many protocols are defined at the application layer of the TCP/IP model. The application layer sits at the top of the TCP/IP layer stack, directly above the transport layer. The application layer provides the user an interface and a connection to the network. Many application layer protocols follow the client/server approach.

IPv6 Addressing Types:

•Unicast address •Unspecified address •Loopback address •Multicast address •Anycast address