AT&T Turns to RPR for MAN Multiservices

Resilient Packet Ring (RPR), a small technology with broad implications,
took the spotlight Monday when carrier AT&T said it would
use it to push a cheaper and more scalable version of Ethernet
for any-to-any Local Area Network/Metropolitan Area
Network (LAN/MAN) interconnections.

The company also expects to eventually make it available for Wide Area
Networks
(WAN) as well.

AT&T’s new Ultravailable Managed OptEring Service — currently undergoing a
controlled introduction in New York City — utilizes RPR technology to
offer efficient support for ring topology and fast data
recovery.

Ring topology is often described as an expensive and
difficult-to-install closed loop configuration of networked devices, so
that each device is connected directly to two other devices, one on either
side of it. They are useful for spreading high bandwidth near and far
across a network.


RPR, well on its way to becoming an Institute of Electrical and Electronics
Engineers (IEEE) standard (the IEEE advanced the IEEE 802.17 technical
specification to working group ballot on Nov. 22), is a Layer 2
data-link protocol which provides media access control (MAC) for packets
transported over a ring topology.

AT&T said the new service would allow businesses with multiple locations
in a metropolitan area or campus environment to interconnect the sites as a
private or virtual local area networks, and would give customers highly
available transport of data, packet video and voice over ring topologies.

This, in turn, allows AT&T to provide access to applications such as
storage, data mirroring and hosting in a virtual network environment.
Businesses can also use the service for Internet access by connecting a
business location to an AT&T POP.

AT&T’s support may lend strength to the technology, which critics have
predicted would never attract carrier attention.


The promise of RPR is to bring together
legacy time-division multiplexing (TDM) and packet-data services, and to
use metro fiber rings to transport voice, video and data more efficiently
than the two current approaches — Synchronous Optical Networks (SONET) and
Ethernet — can handle alone.


A ring topology — which Ethernet was not designed to handle — uses sub 50
millisecond protection switching in case of a catastrophic event such as a
fiber cut or link failure. With RPR as part of the protocol stack, Ethernet
can handle ring topologies, allowing RPR to serve as a link that can
combine the resilience and availability of SONET with Ethernet’s simpler
equipment stacks and lower costs.

In addition, RPR promises bandwidth multiplication through “spatial reuse.”
In other words, Ring bandwidth can be reused for different traffic streams
on separate parts of the ring. It also promises additional
bandwidth-utilization efficiency through statistical multiplexing of
traffic, while featuring LAN-like service provisioning.

AT&T plans to make that capability a selling point of the OptEring service,
noting that spatial reuse of bandwidth within a fully meshed fiber
infrastructure will allow businesses greater fiber utilization on fewer
service channels. The company also noted that customers will be able to use
Ethernet and TDM services on the same network infrastructure.

The Ultravailable Managed OptEring service features up to a 99.999 percent
service-level agreement, and supports transport at speeds of 10 Mbps, 100
Mbps and 1 Gbps over fiber rings.


“The suite of AT&T optical Ethernet services responds to the challenges
facing businesses today, including increasing bandwidth demands,
convergence to IP, reducing network complexity and protecting their
existing network investments,” said Eric Shepcara, AT&T vice president for
application integration networking.

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