Little Phone Cards

Aug 10, 2009 at 15:51 o\clock

Supporting VoIP Solutions with Traffic-Engineered MPLS

by: littlephonecards   Category: VoIP   Keywords: VoIP, VoIP, telephony, IP, telephony, internet, telephony, VoIP, phone, cards, VoIP, calling, cards, phone, cards, calling, cards, international, calls

MPLS is widely recognized as the most modern approach to providing the network functionality required by VoIP and other real-time applications. MPLS combines layer 2 and layer 3 technologies to support a mix of services. From the lower-layer ATM and PSTN technologies, MPLS has borrowed the concepts of simple label lookup-based packet forwarding, a-priori out-ofband forwarding path allocation, and service-time resource commitment. From the layer 3 IGP and Differentiated Services QoS framework, MPLS borrows the concept of advertising network topology and link attributes and providing multiservice forwarding paths to mitigate network complexity and enhance scale.

Traffic Engineered MPLS technologies have been designed from the start to address the complexities and high availability requirements of carrier-grade VoIP and other premium services. Fast re-route, auto-bandwidth provisioning, and virtual path TE tunnels are some of the MPLS capabilities that guarantee the high level of quality and reliability that we expect from telephony services.

MPLS defines label-switched paths, which are simple uni-directional forwarding paths constructed by wrapping ATM, IP, and other transport protocols packets in MPLS frames. MPLS identifies each frame with a label. The ingress label edge router (LER) provisions the labels and distributes them to label switching routers (LSR) using a signaling protocol such as LDP or Resource Reservation Protocol-traffic engineering (RSVP-TE) prior to enabling transport across the path. The label distribution process involves an automated sequence of resource requests and acknowledgements that create a path between two points in the network. When using RSVP-TE, QoS parameters may be specified as a requirement to each LSR. When acknowledged, these QoS parameters represent an agreement to provide that level of QoS, or FEC, to packets forwarded along the path.

Service providers can construct customized LSPs that support specific application requirements. Network managers can design LSPs to minimize the number of hops, meet certain bandwidth requirements, support precise performance requirements, bypass potential points of congestion, direct traffic away from the default path selected by the IGP, or simply force traffic across certain links or nodes in the network.

An important benefit of the label-swapping forwarding algorithm is its ability to take any type of user traffic, associate it with an FEC, and map the FEC to an LSP that has been specifically designed to satisfy the FEC’s requirements. Adding DSCP support to the MPLS network allows the network to populate a single LSP with multiple FECs.

The MPLS-TE approach also enables network administrator to provision MPLS fast reroute (FRR) paths for LSPs and associated backup paths while minimizing physical LSR overlap between primary and backup paths. FRR limits path outage times to milliseconds by pre-negotiating resource borrowing from LSR neighbors and localizing the event signaling that implements the FRR operation.

Deploying technologies based on label-swapping forwarding techniques offers network administrators precise control over traffic flow in their networks. This unprecedented level of control results in a network that operates more efficiently and provides more predictable service.

Source: Juniper Networks, Inc. White Paper

Aug 5, 2009 at 15:53 o\clock

How VoIP Works

by: littlephonecards   Category: VoIP   Keywords: voip, internet, telephony, claling, cards, phone, cards

Voice over Internet Protocol (VoIP) is a technology for communicating using “Internet protocol” instead of traditional analog systems. Some VoIP services need only a regular phone connection, while others allow you to make telephone calls using an Internet connection instead.
 
Some VoIP services may allow you only to call other people using the same service, but others may allow you to call any telephone number - including local, long distance, wireless, and international numbers. 
 
VoIP converts the voice signal from your telephone into a digital signal that can travel over the Internet.

If you are calling a regular telephone number, the signal is then converted back at the other end. Depending on the type of VoIP service, you can make a VoIP call from a computer, a special VoIP phone, or a traditional phone with or without an adapter. In addition, new wireless "hot spots" in public locations such as airports, parks, and cafes allow you to connect to the Internet, and may enable you to use VoIP service wirelessly.
 
If your VoIP service provider assigns you a regular telephone number, then you can receive calls from regular telephones that don’t need special equipment, and most likely you’ll be able to dial just as you always have.