The Customer
Mercury Communications Limited
is one of the UK's biggest success stories of the last decade. Mercury
was the first company to offer an alternative service to British
Telecom and now provides a wide range of national and international
services to both residential and business customers. With business
line sales up 20% on last year, and over 100 direct routes to other
countries, Mercury has become the 16th largest international traffic
carrier in the world.
The Challenge
In the UK, Mercury had 44 regional telephone exchanges
(or "switches"). An interactive connection had to be maintained to
each switch in order to configure individual user requirements (customer
datafill), monitor traffic, and collect statistics.
Previously, this switch management was performed from
14 regional centers by Mercury support staff. These centers were connected
to their switches using a variety of hardware systems: terminal servers,
modems, and X.25.
In order to improve the service and reduce the workload,
Mercury decided to rationalize switch management into three centralized
systems: CDMS, SIC and SAC.
- CDMS (Customer Datafill Management System) enables Mercury
users to access and configure remote switches.
- SAC (Switch Access
Computer) controls and logs all interactive switch access, and allows
tracking and correction in the event of error.
- SIC (Statistical
Information Collector) collects, processes and stores all statistical
data output by the switches. Analysis of this data enables Mercury
to monitor the traffic on its switches and provide the best service
to its customers.
Each system required its own dedicated server. Mercury was then faced
with two serial connectivity problems to overcome: how to connect each
system to all 44 switches, and, in the case of CDMS, how to connect
the 200-plus people who logged in and used the system.
The Solution
Mercury chose the Perle RIO product to solve both problems.
RIO is a sophisticated serial I/O solution with support for 512 high-speed
connections, flexible configuration and a data security features unrivalled
in the serial I/O market.
Each switch management system required four serial connections
to each of the 44 switches - a total of 156 connections per server
- with room for expansion as more switches were added to the system.
In each server, Mercury use two RIO Host serial cards and 21
8-port Remote Terminal Adapters (RTAs) to connect to its switches.
Each 8-port RTA connects to two switches, four ports to each. Connection
to the switches is via 64K X.21 leased lines.
RIO's unique fault tolerance enables additional, standby
links to be installed between RTAs. If any link cable fails or is accidentally
disconnected, a connection is maintained via one of the standby fault
tolerant links. This way no switch can become isolated.
A further RIO host serial card installed in the CDMS server
and another seven RTAs provide access for 200-plus users. Five of the
RTAs handle users in the same building - all using Apple Macs. RIO's
modular and flexible nature means that they can locate each RTA within
actual workgroups. And using RTA/P modules, which provide seven serial
ports and one parallel port, means that each workgroup can have its
own parallel printer. The sixth RTA is connected to a pool of modems
for dial-in access by homeworkers, and the seventh RTA is installed
via LDM on another London site.
Benefits
One of the reasons for choosing RIO was its performance.
Mercury's SIC system, in particular, had to be able to cope with a
very high volume of traffic. All 44 switches download half a megabyte
of data each every 15 minutes. That's 22 megabytes suddenly arriving
on the server at the same time. The data takes three to four minutes
to download, but because RIO handles so much of the workload, the host
CPU can collate and store all the data in real-time.
"RIO handles it like a dream," enthused
John Sizeland, Chief Engineer at Mercury's Hardware and Communications
center in London.
"We did our best to break it...in fact we spent a whole weekend
trying to overload the system, but gave up once we had reached twice
our worst case scenario."
The Ethernet and X.25 solutions that Mercury looked at
just couldn't handle this level of traffic. Sizeland described them
as "cumbersome".
This is due to RIO's award-winning use of transputer
technology. The RIO host serial card and each RTA employ a RISC-based Inmos
T225 Transputer. The transputer provides four highspeed RS422 communications
channels (RIO "Links"). Thus, each RIO system runs off an impressive
10Mbit/s serial backbone - as fast as Ethernet but sustainable for
greater distances.
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