Saturday, August 20, 2011

IP Telephony Vs Public Switched Telephone Network

Looking back at the public switched telephone network, which until now has roughly an access network including the wiring from the subscriber's home to the local exchanges and the necessary equipment, a transmission system which includes superior power and communication links between them.

As indicated above all the resources to intervene in the development of a telephone conversation cannot be used by another call until the first does not finish.

In IP telephony, fundamental change occurs in the transmission system: Now this task is carried out by a network based on IP protocol, packet switching, including the Internet. As for the access network may be the same as in the previous case, physically speaking (local loop), but in terms of services is evident that the advantage is geared towards the ability to exchange data, sending images, graphs and videos, as he is talking to someone.

The necessary elements so that they can make voice calls through an IP network depends largely on which terminal is used at both ends of the conversation.

These can be IP or IP terminals. Among the first is the IP phone, a multimedia computer, an IP fax, among the latter is a conventional telephone, a conventional fax, the former are able to deliver to its output the telephone conversation in IP packet format, as well as being part own IP network, the latter not lie, so you need an intermediate device to do this before connecting to the IP network transport.

It should be noted that in the event that one or both ends of the telephone communication are IP terminal, it is important to know how they are connected to the Internet. If you permanently, we can establish communication at any time. If a non-permanent, for example, through an Internet service provider (ISP) via conventional modem (dial-up access), communication is only possible at the time the dial-up user is connected Internet.

Voip Bandwidth Consumption

Bandwidth Consumption in Voip: Achieving high quality carry voice over IP telephone in real time is not an easy task to achieve because such work requires management capabilities that allow network traffic control, real time protocols (TCP/IP are not) and bandwidths "engaged" during the time it takes the completion of the call.

However, day to day limitations on the services of IP-based voice, are being overcome by two factors: improvements in compression algorithms (which allow the optimal use of bandwidth) and the sophistication and development of existing routing protocols (capable of taking into account the delay for each of the possible paths that can take the package to determine the best route you can take, provide reserves bandwidth while tough talk and give preference to packet processing within the router, so that those of high priority are processed first).

VoIP Gateways: Addressing, Routing, RSVP, ATM

Voip Addressing: Taking again the example of an intranet with IP addressing, we could see that the voice interfaces appear as additional IP hosts, as extensions of existing numbering scheme or as new IP addresses.

The translation of the dialed digits to the host IP PBX are made by means of the numbering plan. The destination phone number or any part of this is linked to the destination IP address. When the number is received from the PBX router compared with those who have already been linked with an IP address and are listed in the routing table, if any match the call will be routed to the IP host to which this related, after the connection is established, a link to the intranet is transparent to the subscriber.

Voip Routing: One of the strengths of IP is the sophistication and development of their routing protocols. A modern routing protocol like EIGRP, is able to take into account the delay for each of the possible paths that can take the package and determine the best route you can follow. Advanced features such as the use of routing policies and use of access list (access lists), makes it possible to create highly secure routing schemes for voice traffic.

RSVP: Can be used by VoIP gateways, so as to ensure that traffic will go through the net for the best and shortest way, this may include segments of networks such as ATM or switched LANs. Some of the most important developments are IP routing, development of so-called tag switching and IP switching other techniques.

The sample tag into widespread switching IP routing, policies and capabilities of RSVP over ATM and other transport high. Another benefit of the tag switching is the traffic handling capacity, which is necessary for efficient use of network resources. The traffic management (traffic engineering) can be used to shift the burden of this in different sectors of the network based on different predictions depending on time of day.

Voice over IP - VoIP Compression and Signaling

Voice Compression: The compression algorithms used in gateways analyze a block of PCM samples delivered by the voice encoder (voice codec). These blocks have a variable length depending on the encoder, for example the basic size of a block of G.729 algorithm is 10 ms, while the basic size of a block of G.723.1 algorithm is 30ms.

The chain analog voice is digitalized in PCM frame, and so delivered the same compression algorithm at intervals of 10 ms.

VoIP signaling: Has 3 distinct areas: signaling the PBX to the router, signaling between the router and router to the PBX signaling. For example for a corporate intranet, this appears as the backbone to the PBX, which will give the signal to intranet users. Therefore the PBX forwards the digits to the router in the same way that the digits had been forwarded to a central telephone switch.

When the remote router receives the call requesting Q.931, this sends a signal to the PBX. After the PBX sends an acknowledgment, the router sends the dialed digits to the PBX, and process a call acknowledgment to the source router.

In a network architecture is not connection-oriented (like IP), responsibility for establishing communication and signaling is the end stations (end stations). To successfully provide voice services through a IP re, it is necessary to make improvements in signaling.

For example, an H.323 agent is added to the router to provide support for the transport of audio and signaling networks. The Q.931 protocol is used for the establishment and disconnection of the call between terminals agents or h.323. RTCP (RTP Control Protocol) is used to establish channels of audio. A reliable protocol connection oriented, TCP is used between end stations to carry the signaling channels.

RTP transport protocol in real time, which is supported on UDP, is used for the transport of audio stream in real time. RTP uses UDP as a transport mechanism because it has less delay than TCP, and because voice traffic today, whether they are data or signaling, tolerate lower levels of loss and lack the ease of transmission.

Wednesday, July 6, 2011

Mobile VOIP Technology For Smart Phones

Use of VoIP technology on your mobile phones is nothing new. This has been going on since it was actually discovered. Now use of Voip in smart phones has gained so much popularity like never before. So if you want to remain updated with this latest trend in mobile and communications technology, then be with me and I will tell you what is the future of VOIP technology for phones and how this actually came into existence. Keep reading my detailed post about Mobile Voip on hubpages: Mobile VoIP - The New Evolution in Phones

Thursday, June 2, 2011

Low Cost VPN or Virtual Private Networks

Until not long ago, the different branches of a company could have, each, a LAN to the branch that operates in isolation from the others. Each of these local networks had their own naming scheme, its own email system, and even using protocols that differ from those used in other branches. That is, in every place there was an entirely local settings, which should not necessarily be compatible with any or all other configurations of the other areas within the same company.

As the computer was being built for businesses, the need arose to communicate the different local networks to share internal company resources. To meet this objective, there was the need of a physical medium for communication and this medium were the telephone lines, with the advantages of very high availability ensuring privacy.

In addition to communication between different branches, it became necessary to provide access to mobile users in the enterprise. Through Remote Access Services (RAS), such user can connect to the corporate network and use the resources available within it.

The major drawback of using telephone lines is their high cost, since they usually charge a monthly fee plus a usage fee, which takes into account the duration of calls and the distance to where they are made. If the company has branches within the same country but in different area codes, and also has branches in other countries, telephone costs can become prohibitive. Additionally, if mobile users must connect to the corporate network and not within the area of the company, must make long distance calls, which increased costs.

The Virtual Private Networks (VPNs) are an alternative to WAN via telephone lines and the RAS service, lowering costs and providing the same services using authentication, encryption and the use of tunnels for connections.

Planning to buy VOIP, compare providers here

Friday, March 18, 2011

What is a hard drive?

A hard disk is a storage device which is one of the most integral parts of a computer. Hard disk is a part of computer which contains the encoded information and stores various programs and files. This system operates digital storage in discs which are rapidly rotating magnetic surfaces. In a computer, the disk drive is one of the essential parts and is the primary file storage. The hard drive is so named in order to differentiate it from the diskette or floppy disk which has a lower storage capacity that hard disk. The hard disk drive is able to store a large amount of data in form of gigabytes while traditional floppy disks stored only 1.4 megabytes (now obsolete with the advent of the popular USB flash drive or memory with large storage capacity, durability, and reduced size). According to tech gurus and experts, the future of storage devices are high capacity USB Flash drives.

The hard disk is a series of discs or plates that are located within an outer cover. These covers, which are usually 2 or 4, although there may be up to 7, are made of aluminum or glass and whirling all the time, driven by a motor. The plates are read by the read/write head, which is a set of arms that are aligned vertically so that they can not move independently, but all at once. Each plate is read by two arms that have at their tips a read/write device and they read each side of the plate. Usually there are 8 heads for 4 covers. The heads never touch the plate, because it could cause much damage considering how fast they spin.

The discs consist of tracks, which are the circumference of each face, like a vinyl record. The heads move from the outer track, called track 0, to the inner track. The tracks are lined up in every disc. The set of vertically aligned tracks on each cylinder plate is called. The tracks are divided into sectors that do not have a fixed size. Normally, sectors are 512 bytes (the smallest units of memory).

The performance of a hard disk is measured by different factors. One is the access time, which is the time when the device starts to send data after receiving the order. The access time is the sum of seek time, latency, and time taken for reading and writing. The search time is that it takes the head to reach the target track. Latency is the time to wait for the disk to rotate until the desired sector passes through. Finally, the read/write time is the delay in locating the data controller, read and send new information to the computer. Another important factor is the hard disk transfer rate is the rate at which information is transferred to the computer after it reaches the desired track and sector.