Header Frame Relay

Frame Relay merupakan suatu layanan data paket yang memungkinkan beberapa pengguna menggunakan satu jalur transmisi pada waktu yang bersamaan. Untuk lalu lintas komunikasi yang padat, Frame Relay jauh lebih efisien daripada sirkit sewa (leased line) yang disediakan khusus untuk satu pelanggan (dedicated), yang umumnya hanya terpakai 10% sampai 20% dari kapasitas lebarpita (bandwidth)-nya. Dalam teknik telekomunikasi, penyakelaran paket (packet switching) dikembangkan untuk memenuhi komunikasi data yang sifatnya cepat dan akurat. Sebuah paket dapat digambarkan seperti sebuah amplop atau sampul surat tercatat; mempunyai alamat tujuan, alamat pengirim atau alamat kembali jika kiriman tidak sampai, dan tentu saja isi pesannya atau berita-nya sebagai hal yang pokok. Dalam paket yang berisi data elektronik, masih dilengkapi dengan deteksi kesalahan, ada pula konfirmasi dari si penerima dalam bentuk kode yang dikirim kembali ke pengirim, apakah paket dapat diterima secara utuh. Pada paket data ini ada istilah frame (bingkai) yakni yang menyatakan batas bingkai sebuah paket. Batas frame ditandai dengan flag. Demikianlah sehingga data dibawa sepanjang jalur komunikasi dalam bentuk frame-frame. Struktur dasar sebuah frame adalah seperti terlihat pada



Keterangan:

GFI = General Format Identifier
LCN = Logical Channel Number
LGN = Logical Channel Group Number
PKT TYPE ID = packet type identification
FCS = Frame check sequence
DLCI = data link connection Indentifier
C/R = Command/response field bit
(application specific-not modified by network)
FECN = Forward Explicit Congestion notification
BECN = Backward Explicit Congestion notification
DE = Discard Eligibility Indicator
EA = Address Extension
(allow indication of 3 or 4 byte header)

Penjelasan Gambar: (a) Struktur dasar frame, (b) Field informasi pada X.25
(c) Struktur frame pada Frame Relay, dan (d) Format header pada Frame Relay Gambar 1a, sedang Gambar 1b menyatakan uraian isi information field pada paket X.25. Gambar 1c dan 1d masing masing menyatakan struktur frame dan header (kepala paket) pada Frame Relay. Header merupakan data tambahan pada informasi yang dikirimkan, berisi tanda pengenal pengirim maupun penerima serta tanda-tanda lain yang diperlukan untuk menjamin penyampaian yang benar dari seluruh informasinya (lihat Gambar 1b dan 1d).
Standar internasional untuk akses jaringan dengan penyakelaran paket yang pertama muncul adalah X.25, yang direkomendasikan oleh CCITT (kini ITU-T) pada tahun 1976. Frame Relay yang muncul setelah X.25 ternyata jauh lebih efektif daripada X.25, karena X.25 kerjanya menjadi lambat karena adanya koreksi dan deteksi kesalahan. Frame Relay memiliki sedikit perbedaan; ia mendefinisikan secara berulang header-nya pada bagian awal dari frame seperti terlihat pada Gambar 1d, sehingga dihasilkan header frame normal 2-byte (satu byte atau octet terdiri dari delapan bit). Header Frame Relay dapat juga diperluas menjadi tiga atau empat byte untuk menambah ruang alamat total yang disediakan. Dalam gambar-gambar yang mengilustrasikan jaringan-jaringan Frame Relay, piranti-piranti pengguna ditunjukkan sebagai pengarah-pengarah LAN, karena hal tersebut merupakan aplikasi Frame Relay yang berlaku secara umum. Tentu saja mereka dapat juga merupakan jembatan-jembatan LAN, Host atau front-end processor atau piranti lainnya dengan sebuah antarmuka Frame Relay.
Header Frame Relay terdiri dari deretan angka sepuluh bit, DLCI (Data Link Connection Identifier)-nya merupakan nomor rangkaian virtual Frame Relay yang berkaitan dengan arah tujuan frame tersebut. Dalam hal hubungan antar kerja LAN-WAN, DLCI ini akan menunjukkan port-port yang merupakan LAN pada sisi tujuan yang akan dicapai. Adanya DLCI tersebut memungkinkan data mencapai simpul (node) Frame Relay yang akan dikirimi melalui jaringan dengan menempuh proses tiga langkah yang sederhana yakni:

* Memeriksa integritas dari frame-nya dengan menggunakan FCS (Frame Check Sequence). Jika melalui pemeriksaan ini diketahui adanya suatu kesalahan, frame tersebut akan dibuang.
* Mencari DLCI dalam suatu tabel. Jika DLCI tersebut tidak didefinisikan untuk link (hubungan) yang dimaksud, frame akan dibuang.
* Mengirim ulang (disebut mrelay) frame tersebut menuju tujuannya dengan mengirimnya ke luar, ke port atau trunk (jalur) yang telah dispesifikasikan dalam daftar tabelnya.

Dengan demikian, simpul Frame Relay tidak melakukan banyak langkah pemrosesan sebagaimana halnya dalam protokol-protokol yang mempunyai keistimewaan penuh seperti X.25.

are mars can be lived by us?

Indonesian version

acquaintance with the planet Mars

This planet is the 4th closest planet from the sun. The apparition of the planet is reddish so often referred to as the red planet. This planet has 2 satellites, namely Phobos and Deimos. This planet for 687 days in orbit around the sun. This planet also rotates. When rotation is 25.62 hours. Mars similar to Earth's size, but smaller. Characteristics are almost similar to Earth's!

What's on MARS?

Acquainted with the TCP / IP

Indonesian Version

History

History of TCP / IP commencement of the birth of the ARPANET packet switching network is digital, funded by DARPA (Defense Advanced Research Projects Agency) in 1969. Meanwhile, the ARPANET continued to increase in size so that the protocol used at that time could no longer accommodate the number of nodes is more and more. Therefore, DARPA funded the creation of the more common communication protocols, namely TCP / IP. He was adopted into the standard ARPANET in 1983.

To facilitate the process of conversion, DARPA is also funding a project that implements this protocol into BSD UNIX, so began the marriage of UNIX and TCP / IP .. At first the internet is used to refer to networks that use internet protocol (IP) but with the development of networks, the term is now a generic term used for all classes of networks. Internet is used to refer to communities worldwide computer networks that are interconnected with TCP / IP.


Excellence

The development of TCP / IP is widely accepted and practically become de-facto standard computer network-related traits contained in the protocol itself, which is keunggulun of TCP / IP, namely:

• The development of TCP / IP uses an open protocol standard that is widely available. Everyone can develop software to be able to communicate using this protocol. This makes use of TCP / IP extends very quickly, especially in terms of adoption by a variety of operating systems and network applications.
• Not dependent on the hardware or operating system specific network so TCP / IP suitable for bringing together a wide range of networks, eg Ethernet, token ring, dial-up line, X-25 net and others.
• How the addressing is unique on a global scale, allowing the computer to uniquely identify the other computers in the entire network, even though its network of worldwide Internet network. Every computer connected to a TCP / IP (Internet) will have an address that belongs only to him.
• TCP / IP routing has the facilities and other types of services that enable applied to the internetwork.

Architecture and Network Protocol TCP / IP

In a computer network architecture, there is a layer-layer (layer) which has a specific task and has its own protocol. ISO (International Standards Organization) has issued a standard for computer network architecture known as the Open Systems Interconnection (OSI).

Comparison of Architecture OSI and TCP / IP
Although the numbers vary, but all the functions of the layers of the OSI architecture are covered by the architecture of TCP / IP. The details of the function of each layer architecture of TCP / IP is as follows:

• Physical Layer (physical layer)
Is the lowest layer that defines the physical quantities such as media communications, voltages, currents, etc.. This layer may vary depending on the medium of communication on the network in question. TCP / IP is flexible so it can integrate the integration of various networks with physical media is different.

• Network Access Layer
function similar to the OSI Data Link layer. These layers organize the distribution of data frames on the physical medium is reliable. This layer usually provides services for error detection and correction of data transmitted. Some examples of protocols used at this layer is X.25 public network, Ethernet for networking Etehernet, Package Radio AX.25 networks and so on.

• Internet Layer
defining how the relationship can occur between two parties that are on different networks such as the Network Layer of the OSI. On the Internet network that consists of tens of millions of hosts and hundreds of thousands of local networks, this layer is responsible for ensuring that a packet that is sent to find the goal wherever located. Therefore, this layer has a particularly important role in realizing internetworking covering large areas (worldwide Internet). Some of the important task at this layer are:
1. Addressing, which complement each datagram with the Internet address of the destination. Addresses on this protocol known as Internet Protocol Address (IP Address). Because the addressing (addressing) on ​​the network TCP / IP is at this level (software), then the TCP / IP network independent of the type of media and computer use.
2. Routing, which determines where the datagram will be sent in order to achieve the desired goal. This function is the most important functions of the Internet Protocol (IP). As a protocol that is connectionless, the routing process is fully determined by the network. Sender has no control over it sends packets to reach the goal. Routers on the network TCP / IP is very crucial in the delivery of datagrams from the receivers to a destination.

• Transport Layer
define the ways to perform data transmission between end to end hosted reliably. This layer ensures that the information
received at the receiver side is equal to the information submitted to the sender. To that end, this layer has several important functions, among others:

1. Flow Control. Delivery of data that has been broken down into packets must be so arranged so that the sender not to transmit data at speeds that exceed the ability of recipients to receive the data.

2. Error Detection. Sender and receiver also complement the data with some information that could be used to check the data transmitted is free from error. If you found an error in the received data packet, the receiver will not accept data. Sender will retransmit the data packets that contain errors earlier. However, this can cause significant delay.

In the TCP / IP, the protocol used is the Transmission Control Protocol (TCP) or User Datagram Protocol (UDP). TCP is used for applications that require reliability data, whereas UDP is used for applications that require short packet length and does not demand high reliability. TCP has a function of flow control and error detection and connection-oriented nature. In contrast to the UDP which is connectionless there is no mechanism to check data and flow control, so called unreliable UDP protocol. For some matters relating to the efficiency and simplification, some applications choose to use UDP as the transport protocol. An example is a database application that merely query and response, or other applications that are highly sensitive to delay such as video conferencing. Such applications can tolerate a bit error (image or sound can still be understood), but would be uncomfortable to be seen if there is a significant delay.

• Application Layer
is the last layer in the architecture of TCP / IP that serves to define the applications that run on the network. Therefore, there are many protocols in this layer, in accordance with the number of TCP / IP applications that can be run. Examples are SMTP (Simple Mail Transfer Protocol) for sending e-mail, FTP (File Transfer
Protocol) for file transfer, HTTP (Hyper Text Transfer Protocol) for web applications, NNTP (Network News Transfer Protocol) for the distribution of news group and others. Each application generally uses TCP and IP protocols, so the whole family is named after the protocol with TCP / IP.

Delivery and Acceptance Data Package

Layers and protocols contained in the network architecture of TCP / IP describes the functions in communication between two computers. Each layer receives data from the layers above or below it, then process the data according to the protocol functions they have and forward it to the next layer. When two computers communicate, there is the flow of data between sender and receiver through the layers above. At the sender, the data flow is from top to bottom. Data from the user or an application sent to the Transport Layer in the form of packets with a certain length. The protocol adds a number of bits in each packet as a header that contains information about the sequence of segmentation to maintain data integrity and pariti bits for error detection and correction.
From the Transport layer, which has given the header data is forwarded to the Layer Network / Internet. In this layer occurs by the addition of protocol header that contains the destination address information, the sender address and other information needed to perform routing. Then there was the direction of routing data, ie to the network and the interface where the data will be sent, if more than one interface on the host. In this layer can also occur segmentation data, because the length of the package to be delivered must be adapted to the conditions of communication media on a network that will be traversed.

Final data will arrive at the Physical Layer which sends the data in the form of electrical magnitudes / physical such as voltage, current, radio waves or light, according to media used.

At the receiver, the data processing is similar as above only in the opposite sequence (from bawqah upwards). Received signal at the physical layer to be changed in the data. The protocol will examine the integrity and if not found error t header that is added will be removed.

Furthermore, the data passed to the network layer. In this layer, the destination address of the packet data received will be checked. If the destination address is the address given host, then the network layer header will be removed and the data will be forwarded to the layer above it. But if not, the data will be forwarded to the destination network, in accordance with routing information owned.

At the Transport layer, the truth of the data will be examined again, using the header information sent by the sender. If no error, the data packets received will be rearranged in this order at the time will be sent and forwarded to the application layer at the receiver.

The process is carried out each layer is known as data encapsulation. Encapsulation is transparent in nature. That is, a layer does not need to know how many layers above it and below it. Each one is only doing his job. At the sender, this task is to receive data from the layer above, processing such data in accordance with the protocol functions, adds protocol headers and forwarding to the layer below.

At the receiver, this task is to receive data from the layer below it, according to the data processing functions of the protocol, the protocol headers are removed and continue to layer on top of it.

Internet Protocol

Internet Protocol (IP) functions delivering data packets to the correct address. Therefore, the Internet Protocol plays a very important part of the network TCP / IP. Because all applications are TCP / IP must be based on Internet Protocol in order to run properly.

IP is a protocol at the network layer are:
1. Connectionless, ie, every packet of data sent at one time going through the route independently. IP packet (datagram) is going through a route that is determined by each router through which the datagram. This allows the entire datagram arrives at its destination in a different order for different route anyway.
2. Or unreliability unreliable IP protocol does not guarantee that the datagram must be sent to the destination. He will only do a best effort delivery that is doing their best so that the packets sent to its destination.

A datagram may not arrive safely to its destination because of the following:
• The bit error during transmission of a datagram to a medium
• The router is skipped mendiscard datagram due to congestion and lack of buffer memory space
• The breakdown in route to a destination for a while due to the router is down
The occurrence of chaos routing, so the datagram looping

IP is also designed to be able to pass through various media of communication that has the characteristics and different speeds. On Ethernet networks, the length of a datagram will be greater than the length of the datagram to the public network that uses the telephone network media, or on the wireless network. This difference is solely to achieve a good throughput on each medium. In general, the faster data transfer capabilities in the media, the greater the maximum datagram length is used. As a result of these differences, the IP datagram can be fragmented when switching from medium to high speed low speed (eg from 10 Mbps Ethernet LAN to a leased line using Point-to-Point Protocol with a speed of 64 kbps). At the router / host recipients, the datagram this fragment that were to be put together again before passing to the next router, or to the transport layer on the destination host. This adds processing time on the router and cause delay.

The whole nature described in the above is the result of the protocol efficiency is sacrificed as a consequence of the superiority IP protocol. These advantages combine the capabilities of the various media of communication with different characteristics, with the development of flexible network, able to change the routing automatically if a route fails, and so on. For example, to be able to dynamically change the routing, the routing mechanism chosen is determined by network conditions and network elements (routers). In addition, the routing process should also be made for each datagram, not only at the beginning of a relationship. Let us consider the structure of the header of the IP protocols and their respective functions.

Each protocol has extra bits beyond the information / data it carries. In addition to information, these bits also serve as a tool of control. In terms of efficiency, the greater the number of these extra bits, the smaller the efficiency of communication that run. Conversely the smaller the amount of these extra bits, the higher the efficiency of communication that are running. Here is done the trade-off between reliability and efficiency datagram. For example, the IP datagram in order to find the goal, it needs additional information to be included in this header.

Acquainted with BNC connectors

indonesian version

BNC (bayonet Neill-Concelman) connector is a very common type of RF connector used for terminating coaxial cable

The use of BNC connectors are used for RF signal connections, for analog and Serial Digital Interface video signals, amateur radio antenna connections, aviation electronics (avionics) and various types of electronic test equipment.
BNC connectors are an alternative to the RCA connector when used for composite video on commercial video devices, although many consumer electronics devices with RCA jacks can be used with BNC only commercial video equipment via a simple adapter. BNC connectors are commonly used on 10Base2 thin Ethernet networks, both on cable interconnections and network cards, although most have been replaced with a new, wired Ethernet device does not use coaxial cable. Some ARCnet network using BNC-terminated coax.

Specification

BNC connector on the 50 and 75 ohm versions. Initially all the 50 ohm cable and used with other impedances, the small mismatch is negligible at low frequencies. 75 ohm types can sometimes be recognized by reduced or absent dielectric in the marriage ended. Various versions are designed to mate with one another, [1] although the impedance mismatch in the cable can cause signal reflections. Typically, specified for use on the frequency of each to 4 and 2 GHz.
BNC75 ohm connectors primarily used for video and DS3 Telco central office applications while 50 ohms and RF is used for data. Convention happening at the BBC on BNC connectors are used for video always 50 ohms may be due to a 50 ohm BNC connectors will damage the socket 75 ohms when connected in error. Many VHF receivers used 75 ohm antenna inputs so Often used 75 ohm BNC connectors. Many receivers use VHF 75 ohm antenna inputs so commonly used 75 ohm BNC connectors.



History

Connectors are named after the bayonet mount locking mechanism and two inventors, Paul Neill of Bell Labs (inventor of the N connector) and Amphenol engineer Carl Concelman (inventor of the connector C), and is much smaller than both N and C connectors. Other backronyms which has BNC picked up over the years include: "Child-Neill Concelman", "Baby N connector", "British Naval Connector", "bayonet Nut Connector", "bayonet Naval Connector". The basis for the development of the BNC connector is the work of Octavio M. Salati, a graduate of the Moore School of Electrical Engineering from the University of Pennsylvania (BSEE'36, PhD'63). He filed a patent in 1945 (awarded 1951) when working at Hazeltine Electronics Corporation to be placed on the coaxial cable connector that will minimize wave reflection / loss.

Similar connectors

Thread J version of the BNC connector, known as the TNC connector (for Threaded Neill-Concelman) are also available. Have superior performance with a BNC connector on the wave frequency.

Triaxial BNC Connector

BNC connectors are commonly used in NIM electronics, but now often replaced with 00 miniature Lemo connector that allows for high densities. For high voltages, MHV and SHV connectors are typically used. MHV connectors are easily mistaken for BNC connectors and can be made to the male by forcing them harshly. SHV connectors are developed as a safer alternative to MHV connector and will not intermate usual with BNC connectors.
In the USSR, has been copied as a BNC connector plug SR-50 (Russian: СР-50) and SR-75 (Russian: СР-75). This connector is slightly different dimensions (as a result of recalculating the Imperial Metric system), but generally are able to BNC, sometimes with the force applied.
Twin BNC (also known as twinax) uses the same connector bayonet latching BNC connector shell as usual, but contains two independent contact points (one male and one female), which allows the connection of 78 ohm or 95 ohm shielded differential pair such as RG-108A . [3] They are capable of operating at 100 MHz and 100 volts. Twin BNC connectors will not intermate usual with BNC connectors.
Triaxial (also known as TRIAX) is a BNC connector on the variant that carries both signal and maintain and ground conductors. It's used in sensitive electronic measuring system, especially from Keithley manufacturing. [Citation needed] The initial designed with extra care just a conductor, but it will be a tri-axial connector also includes three towage arrangements to get rid of an accident forced marriage with a BNC connector. Adaptors that there are a number of possible interconnection between the tri-ax and BNC connectors.

Usefulness

BNC connectors are used for signal connections such as:
• analog and serial digital video signal interface
• amateur radio antenna
• aviation electronics (avionics)
• test equipment.

(Wikipedia.org with some changes)