Communication structure & Communication protocols

Communication protocols describe the set of rules to be used in communication exchange; each one having its own syntax, semantics, and synchronization rules. There are currently two main models for communication protocols being used. The Department of Defense (DOD) went in first with the TCP/IP (Transmission Control Protocol and Internet Protocol) suite in 1970 with which the Internet network evolved. Then the International Organization for Standardization (ISO) effort in the networking domain resulted in the OSI model in 1978. 

OSI (Open System Interconnection) model:

  1. Physical Link: Transportation medium (RS-232, USB, Firewire, Ethernet, optical fiber, radio link)
  2. Data Link: Functional and procedural means of data transfer. Physical addressing and arrangement of bits. (LLC, token bus, x-25, CAN-bus)
  3. Network: Transfer of data sequences and managing routes. (NBF, CNLS)
  4. Transport: Providing reliable data transfer to the upper levels. End-to-end data transfer. Success of data transmission, error check. (TP0,TP1,TP2,TP3,TP4)
  5. Session: Controlling the dialog between terminals. Synchronization of exchanges, session opening and closing. (Half duplex, full duplex, etc.)
  6. Presentation: Formatting and encrypting/decrypting data to be sent on the network. (ASCII)
  7. Application: End user access point, interact with software application. (Modbus)

TCP/IP, a more pragmatic approach from the internet:


  1. Link Layer: The lowest layer (closest to the machine), the physical and logical connection between host and nodes. (Ethernet, IEEE 802)
  2. Internet Layer: Regrouping the methods, protocols, and specification of data packets transportation. (IP for Internet Protocol, using IPv4 or IPv6)
  3. Transportation Layer: Providing end-to-end communication; ensuring reliability, flow control, and multiplexing. (TCP or UDP)
  4. Application Layer: The highest layer (closest to the user) protocols, it uses the transportation and internet layer to establish host-to-host connection. (FTP, HTTP, FMTP, etc.).

Communication Protocol

Communication protocols are formal descriptions of digital message formats and rules. They are required to exchange messages in or between computing systems and are required in telecommunications.

Communications protocols cover authentication, error detection and correction, and signaling. They can also describe the syntax, semantics, and synchronization of analog and digital communications. Communications protocols are implemented in hardware and software. There are thousands of communications protocols that are used everywhere in analog and digital communications. Computer networks cannot exist without them.

Communications devices have to agree on many physical aspects of the data to be exchanged before successful transmission can take place. Rules defining transmissions are called protocols.

 There are many properties of a transmission that a protocol can define. Common ones include: packet size, transmission speed, error correction types, handshaking and synchronization techniques, address mapping, acknowledgement processes, flow control, packet sequence controls, routing, address formatting
Popular protocols include: File Transfer Protocol (FTP), TCP/IP, User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), Post Office Protocol (POP3), Internet Message Access Protocol (IMAP), Simple Mail Transfer Protocol (SMTP).
  1. Transmission Control Protocol (TCP)
  2. Internet Protocol (IP)
  3. User Datagram Protocol (UDP)
  4. Post office Protocol (POP)
  5. Simple mail transport Protocol (SMTP)
  6. File Transfer Protocol (FTP)
  7. Hyper Text Transfer Protocol (HTTP)
  8. Hyper Text Transfer Protocol Secure (HTTPS)
  9. Telnet
  10. Gopher
Let's discuss each of them briefly:
  1. Transmission Control Protocol (TCP): TCP is a popular communication protocol which is used for communicating over a network. It divides any message into series of packets that are sent from source to destination and there it gets reassembled at the destination.
  2. Internet Protocol (IP): IP is designed explicitly as addressing protocol. It is mostly used with TCP. The IP addresses in packets help in routing them through different nodes in a network until it reaches the destination system. TCP/IP is the most popular protocol connecting the networks.
  3. User Datagram Protocol (UDP): UDP is a substitute communication protocol to Transmission Control Protocol implemented primarily for creating loss-tolerating and low-latency linking between different applications.
  4. Post office Protocol (POP): POP3 is designed for receiving incoming E-mails.
  5. Simple mail transport Protocol (SMTP): SMTP is designed to send and distribute outgoing E-Mail.
  6. File Transfer Protocol (FTP): FTP allows users to transfer files from one machine to another. Types of files may include program files, multimedia files, text files, and documents, etc.
  7. Hyper Text Transfer Protocol (HTTP): HTTP is designed for transferring a hypertext among two or more systems. HTML tags are used for creating links. These links may be in any form like text or images. HTTP is designed on Client-server principles which allow a client system for establishing a connection with the server machine for making a request. The server acknowledges the request initiated by the client and responds accordingly.
  8. Hyper Text Transfer Protocol Secure (HTTPS): HTTPS is abbreviated as Hyper Text Transfer Protocol Secure is a standard protocol to secure the communication among two computers one using the browser and other fetching data from web server. HTTP is used for transferring data between the client browser (request) and the web server (response) in the hypertext format, same in case of HTTPS except that the transferring of data is done in an encrypted format. So it can be said that https thwart hackers from interpretation or modification of data throughout the transfer of packets.
  9. Telnet: Telnet is a set of rules designed for connecting one system with another. The connecting process here is termed as remote login. The system which requests for connection is the local computer, and the system which accepts the connection is the remote computer.
  10. Gopher: Gopher is a collection of rules implemented for searching, retrieving as well as displaying documents from isolated sites. Gopher also works on the client/server principle.


Comments

Post a Comment

Popular posts from this blog

Revocation of Access Rights

Revocation of Access Rights In a dynamic protection system, we may sometimes need to revoke access rights to objects shared by different users. Various questions about revocation may arise: • Immediate versus delayed . Does revocation occur immediately, or is it delayed? If revocation is delayed, can we find out when it will take place? • Selective versus general . When an access right to an object is revoked, does it affect all the users who have an access right to that object, or can we specify a select group of users whose access rights should be revoked? • Partial versus total . Can a subset of the rights associated with an object be revoked, or must we revoke all access rights for this object? • Temporary versus permanent . Can access be revoked permanently (that is, the revoked access right will never again be available), or can access be revoked and later be obtained again? With an access-list scheme, revocation is easy. The access list is searched for any access ri...
Read more

Stable-Storage

Image
Stable-Storage Implementation in Operating system By definition, information residing in the  Stable-Storage  is never lost. Even, if the disk and CPU have some errors, it will never lose any data. Stable-Storage Implementation : To achieve such storage, we need to replicate the required information on multiple storage devices with independent failure modes. The writing of an update should be coordinate in such a way that it would not delete all the copies of the state and that, when we are recovering from a failure, we can force all the copies to a consistent and correct value, even if another failure occurs during the recovery. In these, we discuss how to meet these needs. The disk write operation results to one of the following outcome: Successful completion – The data will written correctly on disk. Partial Failure – In this case, failure is occurred in the middle of the data transfer, so that only some sectors were written with the new data, and the s...
Read more

concurrency control

It’s the ability to run multiple processes or threads at the same time. This requires careful memory management, that is, any application running on it’s own should not interfere with other applications. It’s easy when it’s all yours but it becomes a lot harder to share with others. Then you need to be able to run 2 pieces of code together and schedule these. So that they all get their fair share of time on the CPU. There are other factors that come into play here, for example, when you receive input through something like a network device or a peripheral device like a mouse or keyboard. You have to stop what you were doing and deal with that input. All modern operating systems allow multiple programs to run at the same time. This is called concurrency. A running program is known as a process. In fact modern operating systems even allow a single program to execute different routines at the same time or to put it another way, they allow a process to execute several threads of ...
Read more