What Is PRI ?

Primary Rate Interface (PRI) :

ISDN PRI service is used primarily by large organizations with intensive communications needs. An ISDN PRI connection supports 23 64 kbps B-channels and one 64 kbps D-channel (or 23B+D) over a high speed DS1 (or T-1) circuit. The European PRI configuration is slightly different, supporting 30B+D.

BRI is the most common ISDN service for Internet access. A single BRI line can support up to three calls at the same time because it is comprised of three channels (2B+D). Two voice, fax or data "conversations," and one packet switched data "conversation" can take place at the same time. Multiple channels or even multiple BRI lines can be combined into a single faster connection depending on the ISDN equipment you have. Channels can be combined as needed for a specific application (a large multimedia file transfer, for example), then broken down and reassembled into individual channels for different applications (normal voice or data transmissions).

What Is PRI ?

Primary Rate Interface (PRI) :
ISDN PRI service is used primarily by large organizations with intensive communications needs. An ISDN PRI connection supports 23 64 kbps B-channels and one 64 kbps D-channel (or 23B+D) over a high speed DS1 (or T-1) circuit. The European PRI configuration is slightly different, supporting 30B+D.

BRI is the most common ISDN service for Internet access. A single BRI line can support up to three calls at the same time because it is comprised of three channels (2B+D). Two voice, fax or data "conversations," and one packet switched data "conversation" can take place at the same time. Multiple channels or even multiple BRI lines can be combined into a single faster connection depending on the ISDN equipment you have. Channels can be combined as needed for a specific application (a large multimedia file transfer, for example), then broken down and reassembled into individual channels for different applications (normal voice or data transmissions).

What is BRI?

Basic Rate Interface (BRI):

BRI is the ISDN service most people use to connect to the Internet. An ISDN BRI connection supports two 64 kbps B-channels and one 16 kbps D-channel over a standard phone line. BRI is often called "2B+D" referring to its two B-channels and one D-channel. The D-channel on a BRI line can even support low-speed (9.6 kbps) X.25 data, however, this is not a very popular application in the United States.

What is ISDN?

ISDN [I*SD'N] n. 1. Integrated Services Digital Network. 2. A digital telephone service that provides fast, accurate data transmission over existing copper telephone wiring. 3. The way fast way to go online.

The Basics :

ISDN is based on a number of fundamental building blocks. First, there are two
types of ISDN "channels" or communication paths:
B-channel
The Bearer ("B") channel is a 64 kbps channel which can be used for voice, video, data, or multimedia calls. B-channels can be aggregated together for even higher bandwidth applications.
D-channel
The Delta ("D") channel can be either a 16 kbps or 64 kbps channel used primarily for communications (or "signaling") between switching equipment in the ISDN network and the ISDN equipment

What is MPLS VPN ?

MPLS stands for "Multi-Protocol Label Switching" packet-switching VPN technology. After MPLS VPN is used, incoming data packets are assigned a "label" by a "label edge router (LER)". Such labeled packets are forwarded along a "label switch path (LSP)". Along a LSP, each "label switch router (LSR)" forwards a packet based solely on the instructions of the label. At each hop, the LSR strips off the existing label and applies a new label which tells the next hop how to forward the packet. Finally, the LER at the destination system removes the label and delivers the packet to the destined address.
In a MPLS network, LSP is enforced at every hop along the data path such that a secure path is provided across an IP cloud. Specific IP tunnels can be created throughout MPLS network for individual customer, without the need for encryption or end-user applications. LSP paths are designed for their traffic characteristics, as such, they are very similar to ATM path engineering.
LSPs are not restricted to a particular Layer 2 technology but can be flexibly applied to multiple Layer 2 transports such as ATM, Frame Relay or Ethernet. In this way, MPLS enables LSPs to become end-to-end circuits.

What is MPLS-based IP VPN?

It is a IP VPN deploying MPLS technology to mark, classify, and monitor IP packets. At the ingress side of MPLS network, LER examines and determines whether the incoming packets should be labeled. LER classifies incoming IP traffic with MPLS label. The LER converts IP packets into MPLS packets. When the MPLS packets leave the LER, they are examined by LSR for the presence of labels. LSR will then swap labels according to label instructions. At the egress of the network, the LER removes the MPLS header, reconverts MPLS packet into IP packet and forward it to the destined IP network.

What is difference between IP Routing and MPLS VPN Routing ?

In IP routing as an IP packet travels from one router to the next, every router makes it’s own decision on where the packet should go .Each Router reads the IP packet header, and then runs a routing algorithm against the destination address to determine the next hop. Every router then chooses its own next hop for the packet based on the packets header and the routing algorithm. Routers will assign each packet into a set of “Forwarding Equivalence Classes (FECs)” They will then map each FEC to a next hop.

With MPLS every packet only has its IP layer header examined once, when it enters the MPLS network. After the initial FEC assignment a 32 bit fixed length label(called MPLS Label Header or Shim Header) is inserted into the packet that contains the assigned FEC then is sent to the next hop router with the label attached. The label is of local significance only. When MPLS routers, which are called label switch routers(LSRs), are provisioned they will set up a table of label to FEC mappings. Each FEC is assigned a next hop. A label distribution protocol(LDP) is used to exchange label information between label switch routers that have a direct connection to each other. The protocol usually rides on top of the routing protocol in use by the use of extensions that have been developed for MPLS. As the packet goes from hop to hop across the MPLS network the network layer header no longer has to be examined by every router. Instead, the label is used to determine the next hop and which new label to use.
The old label is replaced with the new label, and the packet is forwarded to its next hop. With MPLS forwarding, once a packet is assigned FEC subsequent routers do no further network layer header analysis; the labels drive all forwarding decisions

This method of packet forwarding has many advantages over IP layer forwarding. Since a packet is assigned to a FEC when it enters the network, the edge label switch router can use any information about the packet in determining which FEC to use, even if the information is not contained in the IP header. Packets with the same destination arriving on different ports of the router can be assigned to different FECs. Conventional forwarding, on the other hand, can only consider information that travels with the packet in the packet header. A packet that enters the network at a particular router can be labeled differently than the same packet entering the network at a different router, and as a result forwarding decisions that depend on the ingress router can be easily made. This cannot be done with traditional forwarding, since the identity of a packet's ingress router does not travel with the packet.

What is T1 Line ?

T-carrier is a generic designator for any of several digitally multiplexed telecommunications carrier systems. T1 seems to mean any data circuit that runs at the original 1.544 Mbit/s line rate. T1 carries 24 pulse-code modulated(PCM), time-division multiplexed(TDM) speech signals each encoded in 64 kbit/s streams, leaving 8 kbit/s of framing information which facilitates the synchronization and demultiplexing at the receiver.T1 is used in North America and Japan.

What is Codec?

Codec is a special library or a program that converts normal audio signal in to digitaly encoded one. Codecs vary in the sound quality, the bandwidth required, the computational requirements.

What is E1 line?

In telecommunications, where a single physical wire can be used to carry many simultaneous voice conversations, worldwide standards have been created and deployed. E-carrier system, which is revised and improved version of the earlier American T-carrier technology. Now it is widely used in almost all countries outside USA, Canada and Japan. The line data rate for E1 is 2.048 Mbit/s (full duplex) which is split into 32 time slots, each being allocated 8 bits in turn. It is a ideal for voice traffic because voice is sampled at the same 8khz rate so E1 line can carry 32 simultaneous voice conversions.