Yellow Calling Card

There are many methods to make a phone call. They include using tariff plans, mobile providers, land lines, Voice over ip, post-paid plan, etc.
Phone phone cards are better any time any day due to the under-listed features they offer you:

Read the rest of this entry »

VoIP is a technology that allows people to make phone calls through the public Internet rather than traditional Public Switched Telephone Network (PSTN). Because VoIP o®ers signi¯cant cost savings with more °exible and advanced features over Plain Old Telephone System (POTS), more and more voice calls are now carried at least partially via VoIP. In fact, consulting ¯rm Frost & Sullivan has predicted that VoIP will account for approximately 75% of world voice services by 2007.

For privacy reasons, people sometimes want their phone conversation to be anonymous and do not want other people know that they have even talked over the phone. The use of VoIP has made it much easier to achieve anonymity in voice communications, especially when VoIP calls are made between computers. This is because VoIP calls between peer computers have no phone numbers associated with them, and they could easily be protected by end to end encryption and routed through low latency anonymizing networks (e.g., Onion Routing [13], Tor [6], Freedom [3], and Tarzan [12]) to achieve anonymity. People intuitively think their computer to computer VoIP calls could remain anonymous if they are encrypted end to end and routed through some low latency anonymizing network. Read the rest of this entry »

The 400 kbps data traffic capability that remains with 40 simultaneous voice calls would definitely be “best effort” traffic as all the priority capabilities of the shared channel would have been used up by the voice traffic.

An analysis of VoIP performance on EV/DO Rev.A is given in an IEEE paper, which indicates that VoIP, over EV/DO Rev.A, can be expected to offer comparable coverage, capacity and voice quality to circuit switched cdma2000 cellular services.

Since an EVRC-A voice codec was used in both the Airvana simulation, and the above referenced analysis, significantly improved voice capacity could be expected with the use of an EVRC-B smart codec which is also optimized for VoIP. Read the rest of this entry »

VoIP networks are vulnerable to many of the same security risks as data networks, including denial of service (DoS) attacks, service theft, tampering, and fraud. Many conventional firewalls cannot combat VoIP attacks because VoIP is implemented at both the signaling and media layers. To secure VoIP solutions, the security device must be able to support VoIP protocols such as SIP, MGCP, and H.323, and to associate state at the signaling layer with packet flows at the media layer. The most secure firewall implementations dynamically open and close ports (often called pinholes) for each specific VoIP call.

This requires the firewall to understand the VoIP signaling protocols used in the network. Otherwise, VoIP calls cannot go through the firewall unless a range of ports are opened – which exposes the network for unauthorized access. Application- Layer Gateways (ALGs), back-to-back user agents that can perform the function of dynamically opening and closing firewalls to maintain security, can often augment security where firewalls fall short. ALGs designed specifically to handle demanding applications such as VoIP can protect against malicious attacks on either VoIP or other systems, and even head off severe system outages due to malfunctioning VoIP devices. Read the rest of this entry »

Before any voice can be sent, a call must be placed. In an ordinary phone system, this process involves dialing the digits of the called number, which are then processed by the telephone company’s system to ring the called number. With VOIP, the user must enter the dialed number, which can take the form of a number dialed on a telephone keypad or the selection of a Universal Resource Indicator (URI), but after that a complex series of packet exchanges must occur, based on a VOIP signaling protocol.

The problem is that computer systems are addressed using their IP address, but the user enters an ordinary telephone number or URI to place the call. Read the rest of this entry »