Definition of terms re: April 28 PRNewswire/Australia
Digitcom is working with regional and national telephone companies, ISPs, and PSTN resellers in Europe and on the Pacific Rim to establish international long distance networks and to deploy its Internet-based telephony products using the company's "IntraVoice" gateway and voice compression technology.
A point-of-presence (POP) is the location of an access point to the
Internet. A POP necessarily has a unique Internet (IP) address. Your
independent service provider (ISP) or online service provider (OSP) has
a point-of-presence on the Internet. POPs are sometimes used as one
measure of the size and growth of an ISP or OSP.
A POP may actually reside in rented space owned by a telecommunications
carrier such as Sprint. A POP usually includes routers, digital/analog
call aggregators, servers, and frequently frame relay or ATM switches.
ATM (asynchronous transfer mode) is a dedicated-connection switching
technology that organizes digital data into 53-byte cells or packets and
transmits them over a medium using digital signal technology.
Individually, a cell is processed asynchronously relative to other
related cells and is queued before being multiplexed over the line.
Because ATM is designed to be easily implemented by hardware (rather
than software), faster processing speeds are possible. The prespecified
bit rates are either 155.520 Mbps or 622.080 Mpbs. IEEE Spectrum reports
that speeds on ATM networks are expected to reach 10 Gbps. Along with
SONET and several other technologies, ATM is a key component of
broadband ISDN (BISDN).
Frame relay is a technology for transmitting data packets in high-speed
bursts across a digital network encapsulated in a transmission unit
called a frame. Frame relay requires a dedicated connection during the
transmission period. It's not ideally suited for voice or video
transmission, which requires a steady flow of transmissions. However,
under certain circumstances, it is used for voice and video
transmission. Frame relay is used on wide area networks and also in
private network environments with leased lines over T-1 lines.
Frame relay is a fast-packet technology, which means that error-checking
does not occur at any transmission stage. The end points are responsible
for error checking. (However, the incidence of error in digital networks
is extraordinarily small relative to analog networks.)
Fast packet switching uses asynchronous transfer mode (ATM) with either
frame relay or cell relay. Frame relay relays packets at the data-link
layer of the Open Systems Interconnection (OSI) model rather than at
the network layer. A frame can incorporate packets from different
protocols such as Ethernet and X.25. It is variable in size and can be
as large as a thousand bytes or more.
The frame relay standard, an extension of the ISDN standards, is CCITT
I.122. A frame relay connection is known as a virtual connection. A
permanent virtual connection is totally dedicated to one origin and
destination pair and can transmit up to 1.544 Mbps, depending on the
capabilities of the pair. A switched virtual connection is also possible
using the public network and can provide higher bandwidths. |
