After invading the world of business, Ethernet addresses the longer distances starting with the metropolitan area. The Metro Ethernet was born of this extension. This solution is supported in different settings but especially by the Forum MEF (Metro Ethernet Forum). [Read more…] about What is Metro Ethernet Networks?
The Ethernet switch or Ethernet FDSE (Full Duplex Switched Ethernet), was born in the early 1990s before the advent of switched Ethernet, shared Ethernet networks were cut into shared subnets autonomous, interconnected by bridges. Therefore, the traffic was multiplied by the number of subnets. [Read more…] about Full Duplex Switched Ethernet (Ethernet FDSE)
Ethernet networks at 10 Mbit/s were the first to be introduced in the market. They still represent a significant proportion, although standards to 100 Mbit/s tend to supplant them. This section reviews the various products of the Ethernet shared working at a speed of 10 Mbit/s. [Read more…] about Ethernet networks at 10 Mbit/s
Random Access, which is to issue a completely random time, relies on the Aloha method. The latter takes its name from an experiment performed on a network connecting the various islands of the Hawaiian Archipelago early 1970. In this method, when a coupler has information to transmit, it sends it without worry about other users. If there is a collision, that is to say superposition of two signals or more users, the signals become indecipherable and are lost. They are subsequently transmitted, as shown in Figure, in which the couplers 1, 2 and 3 collide. The coupler 1 transmits its field first because he shot the smallest timer. Then, the module 2 emits, and its signals collide with the coupler 1. Both derive a random time of retransmission. The coupler 3 is listening while the couplers 1 and 2 are silent, so that the frame of the coupler 3 passes successfully. Technical aloha is the origin of all the random access methods. [Read more…] about Random Access Methods in Computer Networks
Shared Ethernet Networks implementing technical standard access to physical media by the IEEE 802.3 working group under the name MAC access (Medium Access Control). MAC uses a general technique called random access. [Read more…] about What is Shared Ethernet Networks?
The next field contains the reference made to the VCI / VPI (Virtual Channel Identifier / Virtual Path Identifier). The role of virtual paths is to provide semi-permanent connections. [Read more…] about Virtual and virtual path Circuit
As explained above, the cell is formed of exactly 53 bytes, comprising 5 bytes of header and 48 bytes of data. [Read more…] about ATM Cell Structure
SONET/SDH standard was carry telephone speech, and it took many adaptations for the transport of frames and type of IP packets, ATM, or others. The successor of SONET/SDH has been launched in early 2002 and standardized by ITU-T as the OTN (Optical Transport Network). Its role is to channel packages on routes to 2,5, 10 and 40 Gbit/s. The corresponding recommendation G.709 carries the number. [Read more…] about What is OTN (Optical Transport Network) ?
SDH recommendation was standardized by ITU-T (G.707 and G.708): [Read more…] about What is Synchronous Digital Hierarchy (SDH)?
SONET (Synchronous Optical Network) is a physical level standard, proposal by Bellcore (Bell Communications Research) in the mid-80s for transmission through an optical fiber. SONET is a technique of transport between two nodes, which defines the interface adopted for the NNI (Network Node Interface). Standardized by the ANSI and recommended worldwide by the CCITT, SONET can be thought of as a physical network for a global communication system in the same way that a twisted pair LAN can see as the communication system of a corporate network. It is a potentially global network, built on fiber optic cable, with standardized data transmission speeds and recognized worldwide. SONET eliminates limits between telephone companies worldwide.
[Read more…] about What is Synchronous Optical Networking (SONET)? – Definition
To achieve simultaneous multiplexing multiple telephone lyrics on the same circuit, Americans have adopted a standard for multiplexing 24 channels of 64 kbit/s on a support at 1544 Kbit / s. This channel is called DS-1. Europeans have responded to this technique by the E-1 channel multiplexing 30 voice channels on a support 2048 Mbit/s. From this basic multiplexing, a hierarchy has been defined, it is a multiple of the base channel, as in the case of Europe, or a little more complex, as in the US case, because an area of supervision rate-dependent. [Read more…] about What is Plesiochronous media?
The physical layer represents the first level of the hierarchy of the reference model. This level is responsible for transporting the bits on physical media varied. To access a support, use an access interface. [Read more…] about What are the physical layer interfaces?
The Optical Switches are used to connect optical links between them. At incoming optical fibers correspond outgoing optical fibers. If the switch uses an electrical part, the switch is said opto electronics and not only optical. These switches are based on the interconnection of switching elements, that is to say, switches which have two input gates and two output ports as shown in Figure. Connected in series, these elementary switches allow making great switches. The design of these devices, however, poses many problems. [Read more…] about What is Optical Switches?
The idea at the basis of the wavelength routing network consists of maximum reuse the same wavelengths. The figure illustrates a node of a routing network wherein wavelengths of the same wavelength are used repeatedly. [Read more…] about What is Wavelength Routing Networks?
The user generates IP packets, it is necessary to transport these IP packets to the ADSL modem. For this, we use an Ethernet frame, a PPP frame, a USB frame, or a superposition of these frames as a PPP frame encapsulated in an Ethernet frame or a PPP frame encapsulated in a USB frame. [Read more…] about What are the ADSL Protocols?
The metal lines have been used for decades for the transport of the telephone speech with a bandwidth of 3200 Hz. They are used today for transport, at the same time as the telephone, broadband data packets. The xDSL environment is devoted to terrestrial broadband connections, we give here in an introduction. [Read more…] about What is xDSL(Digital subscriber line)?
Another solution to obtain a broadband distribution network is to use the wiring of cable operators, when it exists. This wiring has long been made of CATV (cable TV), whose bandwidth exceeds 800MHz easily. Today, this infrastructure is slightly modified by the introduction of systems HFC (Hybrid Fiber/Coax), combining a fiber portion between the head end and the beginning of the service by the CATV. This topology is illustrated in Figure. [Read more…] about Cable networks (CATV)
When the frames transmitted on the PON are Ethernet, EPON talking. The features of this network are identical to those of the other PON: distribution throughout the network, where only the station specified in the Ethernet frame can retrieve the information conveyed. The standardization of EPON technology is performed by the IEEE 802.3ah group. This group has several objectives, including that of introducing Ethernet in the local loop under the name of EFM (Ethernet in the First Mile). The objective was to replace the ATM technology, very expensive to implement on a multipoint technology, the Ethernet technology. [Read more…] about Ethernet Passive Optical Network (EPON)
On the Passive Optical Network (PON), it is possible to transit ATM cells according to the technique developed by the working group FSAN (Full Service Access Network). This solution was then standardized in G.983 recommendation ITU-T. Both ends of the optical shaft are called OLT (Optical Line Termination) and ONU (optical network unit). For reasons of energy loss, it is not possible to exceed fifty branches on the trunk. The figure illustrates the architecture of a passive optical network. [Read more…] about Passive Optical Network
In a mesh network, the routing of packets is part of a complex algorithm, by the distribution of decisions, which are both space and time. A node should know the status of all the other nodes before deciding where to send a packet, which is impossible to achieve. [Read more…] about What is Routing? Type of Routing.
The function of the network layer is to provide an end-to-end communication capability to the transport layer, which lies above it as shown in Figure. The OSI reference model specifies that the transport layer need not know the method by which the network layer performs communications. [Read more…] about What is the Network Layer? – Definition
The Ethernet frame is designed to transport packets in enterprise networks by an original method for broadcasting on a local network. This solution gave birth shared Ethernet, in which the broadcast frame is transmitted and where only the station that recognizes the right to copy the information. To this solution dissemination has added Ethernet switching. [Read more…] about What is Ethernet Frame?
The LAP-F protocol (Link Access Protocol-Frame) was born with frame relay, designed to improve the performance of networks from the X.25 recommendation UITT. The latter has proved too heavy and therefore unable to increase rates, it took in search for a simplification. [Read more…] about LAP-F protocol
The frame level (layer 2) is to render a service to the next level just. This service is a transport node to node packet. Specifically, its role is to transport a package of three or message fragment layer of layer 4 from one node to another node. For this, the frame level asks his turn at just below, the physical level, a service of conveying the bits of the frame from one node to another node. This section provides the features necessary to achieve all these actions. [Read more…] about Frame-level Architecture
How to encode the digital signal is an important function of coupler communication. This main function is to adapt the signals transmission channel. In the case of local networks, the transmission rate is tens or hundreds of megabits per second. Therefore, the choice of representation Physical data is important. To perform the synchronization bit, that is to say, to ensure that each bit is read at the right time, you need a minimum of transitions are made to extract the clock signal. [Read more…] about The Digitization of Signals
Modulation has defined as the process of combining an input signal m (t) and a frequency carrier FC to produce an S (t) signal whose bandwidth is (usually) centred around FC. In the case of digital data, the justification of the modulation must be clear: it is necessary when there is only the possibility of analogue transmission, to convert the digital data into analogues. However, when the data is analogue, the justification is not so apparent. After all, voice signals are transmitted through telephone lines using their original spectrum (this is called baseband transmission). There are two main reasons: [Read more…] about What is Modulation? Different Types of Modulation Techniques
ISO (International Standardization Organization) standard has its own architecture as the OSI (Open Systems Interconnection). The architecture ISO is the first to be defined, and so relatively parallel to the Internet. The distinction between the two is that the ISO formally defines the different layers architecture, while the Internet architecture is applied to achieve a practical environment. [Read more…] about ISO Architecture
In the 1970s, the Department of Defense, or DOD (Department Of Defense), decided before the proliferation of machines using different, incompatible communication protocols, to define its own architecture. This architecture, called TCP / IP, is the source of the Internet. It is also adopted by many private networks, called intranets. [Read more…] about TCP/IP Architecture
Applications that are conventionally used on terminal equipment put in implement a point-to-point communication, that is to say the part of the communication micro to go look for information to only one other point. Many other applications involve the cooperation of several processes. For example, a search in a distributed database in which information is spread across multiple sites, uses a simultaneous request for information to several centers. To make this request, the application and all associated protocol layers must manage multipoint. This way of communicating is more powerful than that which is to apply a first site, and once the response, a second, and so on. [Read more…] about Multi-point Architectures