Question

1. List four alternate terms for "physical address".

2. Name the TCP/IP model layers, and map them to the corresponding OSI model

layers.

3. At which TCP/IP model layer(s) do UDP and TCP reside?

4. List five TCP/IP model application layer protocols.

Answer 1

Physical address

In IT, a physical address refers to either a memory location, identified in the form of a binary number, or a media access control (MAC) address.

In computing, physical address refers to a memory address or the location of a memory cell in the main memory. It is used by both hardware and software for accessing data. Software, however, does not use physical addresses directly; instead, it accesses memory using a virtual address. A hardware component known as the memory management unit (MMU) is responsible for translating a virtual address to a physical address.

In networking, physical address refers to a computer's MAC address, which is a unique identifier associated with a network adapter that is used for identifying a computer in a network.

Related Terms

• vMem.
• Virtual Address (VA)
• Media Access Control Address (MAC Address)
• Memory Address.
• Rooting.
• Multiprocessor.
• C++
• Digital Down Converter (DCC)

There are two models that are widely referenced today: OSI and TCP/IP. The concepts are similar, but the layers themselves differ between the two models.

Network layers

While TCP/IP is the newer model, the Open Systems Interconnection (OSI) model is still referenced a lot to describe network layers. The OSI model was developed by the International Organization for Standardization. There are 7 layers:

1. Physical (e.g. cable, RJ45)
2. Data Link (e.g. MAC, switches)
3. Network (e.g. IP, routers)
4. Transport (e.g. TCP, UDP, port numbers)
5. Session (e.g. Syn/Ack)
6. Presentation (e.g. encryption, ASCII, PNG, MIDI)
7. Application (e.g. SNMP, HTTP, FTP)

The TCP/IP model is a more concise framework, with only 4 layers:

1. Network Access (or Link)
2. Internet
3. Transport (or Host-to-Host)
4. Application (or Process)

The OSI model, let’s start at the top layer and work our way down.

• Layer 7 (Application): Most of what the user actually interacts with is at this layer. Web browsers and other internet-connected applications (like Skype or Outlook) use Layer 7 application protocols.
• Layer 6 (Presentation): This layer converts data to and from the Application layer. In other words, it translates application formatting to network formatting and vice versa. This allows the different layers to understand each other.
• Layer 5 (Session): This layer establishes and terminates connections between devices. It also determines which packets belong to which text and image files.
• Layer 4 (Transport): This layer coordinates data transfer between system and hosts, including error-checking and data recovery.
• Layer 3 (Network): This layer determines how data is sent to the receiving device. It’s responsible for packet forwarding, routing, and addressing.
• Layer 2 (Data Link): Translates binary (or BITs) into signals and allows upper layers to access media.
• Layer 1 (Physical): Actual hardware sits at this layer. It transmits signals over media.

The TCP/IP model, sometimes referred to as a protocol stack, can be considered a condensed version of the OSI model.

• Layer 1 (Network Access): Also called the Link or Network Interface layer. This layer combines the OSI model’s L1 and L2.
• Layer 2 (Internet): This layer is similar to the OSI model’s L3.
• Layer 3 (Transport): Also called the Host-to-Host layer. This layer is similar to the OSI model’s L4.
• Layer 4 (Application): Also called the Process layer, this layer combines the OSI model’s L5, L6, and L7.

The two most important protocols in the Transport Layer are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). TCP provides reliable data delivery service with end-to-end error detection and correction.UDP provides low-overhead, connectionless datagram delivery service. Both protocols deliver data between the Application Layer and the Internet Layer. Applications programmers can choose whichever service is more appropriate for their specific applications.

User Datagram Protocol

The User Datagram Protocol gives application programs direct access to a datagram delivery service, like the delivery service that IP provides. This allows applications to exchange messages over the network with a minimum of protocol overhead.

UDP is an unreliable, connectionless datagram protocol. As noted, “unreliable” merely means that there are no techniques in the protocol for verifying that the data reached the other end of the network correctly. Within your computer, UDP will deliver data correctly. UDP uses 16-bit Source Port and Destination Port numbers in word 1 of the message header to deliver data to the correct applications process.

Transmission Control Protocol

Applications that require the transport protocol to provide reliable data delivery use TCP because it verifies that data is delivered across the network accurately and in the proper sequence. TCP is a reliable, connection-oriented, byte-stream protocol. Let’s look at each of these characteristics in more detail.

TCP provides reliability with a mechanism called Positive Acknowledgment with Re-transmission (PAR). Simply stated, a system using PAR sends the data again unless it hears from the remote system that the data arrived OK. The unit of data exchanged between cooperating TCP modules is called a segment.

Application Layer

The application layer is present at the top of the OSI model. It is the layer through which users interact. It provides services to the user.

Application Layer protocol

1. TELNET:

Telnet stands for the TELecomunications NETwork. It helps in terminal emulation. It allows Telnet client to access the resources of the Telnet server. It is used for managing the files on the internet. It is used for initial set up of devices like switches. The telnet command is a command that uses the Telnet protocol to communicate with a remote device or system. Port number of telnet is 23.

Command:

telnet [\\RemoteServer]
\\RemoteServer   : Specifies the name of the server to which you want to connect

2. FTP:

FTP stands for file transfer protocol. It is the protocol that actually lets us transfer files.It can facilitate this between any two machines using it. But FTP is not just a protocol but it is also a program.FTP promotes sharing of files via remote computers with reliable and efficient data transfer. Port number for FTP is 20 for data and 21 for control.

Command:

ftp machinename

3. TFTP:

The Trivial File Transfer Protocol (TFTP) is the stripped-down, stock version of FTP, but it’s the protocol of choice if you know exactly what you want and where to find it. It’s a technology for transferring files between network devices and is a simplified version of FTP.

Command:

tftp [ options... ] [host [port]] [-c command]

4. NFS:

It stands for network file system.It allows remote hosts to mount file systems over a network and interact with those file systems as though they are mounted locally. This enables system administrators to consolidate resources onto centralized servers on the network.

Command:

service nfs start

5. SMTP:

It stands for Simple Mail Transfer Protocol. It is a part of the TCP/IP protocol. Using a process called “store and forward,” SMTP moves your email on and across networks. It works closely with something called the Mail Transfer Agent (MTA) to send your communication to the right computer and email inbox. Port number for SMTP is 25.

Command:

MAIL FROM:<[email protected]?