@make[report]
@majorheading[Amdahl]
@section[General]
Amdahl supply a wide range of X.25 equipment which can be put together to
provide extremely large networks.  The equipment is based on a multi-micro
processor architecture and although no store sizes are quoted it is stated
that the largest switch can handle 2000 simultaneous calls, expandable to
6000 calls.
@section[Hardware Description]
The main Amdahl switch, called the 4410 Network Processor is based on a
multi microprocessor design using Computer Automation microprocessors.
Each X.25 line (or pair of low speed lines) is controlled by an I/O Module
containing a CA micro and 64K bytes of local memory.  The I/O Module handles
all of both Level 1 and 2.  The I/O Modules are connected to a Data Movement
Processor.  The PLP has private memory for its code and access to 128K bytes
of public memory for buffers etc.  This entire unit is called an X.25
processor (XPRO) and the larges switch configuration contains three.  
There is a further Node Administrator, a CA mini, to control the parts 
and to handle all the details of call setup and cleardown.  
It is an unusual configuration as there is only
a small amount of global memory, with most of the memory (up to in excess of
7M bytes) being held in the line modules.
@section[Software Description]
All the software is written in assembler.  It is claimed to be modular and
cannot be amended by the 'user'.
@section[Configuration Options]
The smallest switch consists of a single XPRO and Node Administrator and can
be expanded up to 40 lines.  The addition of a second XPRO adds a further 40
links and the third XPRO takes it up to the maximum configuration of 120 lines.
@section[Line Speeds/Interface Options]
The following line speeds are supported for both internal and external
clocking: @begin[verbatim]
       2.4k, 4.8k, 9.6k, 19.2k, 48k, 64k. @end[verbatim]
V24 is used for speeds up to, and including, 19.2k, V35 is used for 48k and 
64k, it was suggested that the way to handle higher speeds was to use a number
of 64 kb/s lines using an Amdahl 2210 multiplexor.
@section[Throughput]
A single XPRO can handle 450 packets/sec (all packets through the Node), a
fully configured Node can handle 1350 packets/sec.  There is also an
aggregate data limit of 300 Kb/s full duplex, rising to 900 Kb/s for the
fully configured node.
@section[Costs]
?
@section[X.25 Facilities]
Fast Select, Packet and Window negotiation, PVCs and Reverse Charging are
supported.  Call Statistics are not currently supported in a PSS compatible 
form.  There are no plans to support Call Redirection.  The maximum packet
size supported is 256.
@section[Multinode Networks]
Amdahl switches are currently used in large multinode networks (AT & T have
50).  A modified form of X.25 is used between the nodes and although the
protocol is not in the public domain, Amdahl would be prepared to release it
to the Academic Community.  Adaptive routing is supported.
@section[Addressing]
A single address is normally used per link, but 'Access Groups' may 
be used to achieve the desired flexibility.  An Access Group is normally
used to create a 'hunt group' effect, in other words it specifies a single
address, or range of addresses (created by an 'n' digit match) followed by
a list of lines corresponding to that address (or range).  Normally the
number of lines would be greater than one but by restricting it to one
line and having a number of access groups all pointing to that line, the
effect of multiple ranges and single addresses is created for a particular
link.

Full load sharing is not supported, if multiple links correspond to an
address or range then a 'round robin' system is used to allocate calls to
the links.
@section[Network Management]
Each node in a network has up to three asynchronous ports for control
purposes.  The first port is used to issue commands to the processor, the
second for monitoring the performance and printing alarms, the third for
the output of billing records.  The functions of any of the ports may be 
combined with those of another so that only one port is mandatory.
In order to perform Network Management of a Network, these ports are connected
into reverse PADs (with an Amdahl PAD, a PVC would then be used) and the PADs
connected to a remote management machine.  Software currently exists for using
an Amdahl mainframe running U.TS as the management machine.  It can be seen
therefore that "simple" X.29 is used as the protocol and full details exist
to allow the Community to use its own host machines as desired.
@section[Statistics]
Statisitcs are collected as required by the spec, however, it is not
currently possible to store them on a disc on the switch.  There is a 
development in hand to attach a 40 Mbyte Winchester (with floppy access)
to a 4410, to be called a 'Z-Disc', which will then allow the collection of
statistics.
@section[Operator Control]
The details noted in the section on network Management apply to control
although the functions can be split as noted above.  It is not possible to
have both local control and remote control simultaneously.  The various
aspects of control as specified are possible on a live system with the
exception of the ability to clear a call to a specified address.  (But
Terry says YES.)
@section[Date-Time Stamp]
Messages are date and time stamped.  If a node crashes, and it is a single
node system, then the current date and time is lost although the date and
time may be changed on a running system.  On a multiple node system, the
date and time is automatically recovered.
@section[PSS Compatibility]
Amdahl do not guarantee compatibility with PSS.  They claim to 'conform to
the spirit' of the CCITT recommendations.  In reality, they claim that they
would amend their software if we discovered differences on our existing
machines.
@section[Performance - Packet Transmissions]
@begin[verbatim]
                Call Requests   80ms
                Data Packets   <10ms
                Clear Request   80ms
@end[verbatim]
Although the Call Request time is rather long, it is handled independantly
of the main swirtching function.
@section[Availability and Reliability]
The switches have been designed with the aim of high availibility.  There
are, for example, three power supplies on each node, if one fails it can
be replaced without stopping the system.  W. H. Smith has 4 (can't
remember when it had failed)  An I/O Module can also be
replaced on a live system.  If an entire XPRO goes down, then it can be
repaired without a reload of the entire node.  Obviously if a Node
Administrator, or its associated bus, fails then the entire node fails.
@section[Operation]
System has been designed to run unattended and meets the spec.
@section[Reconfiguration]
When a system is first installed, Amdahl will have set up an initial
configuration.  It is then possible to change any of the configuration details,
or set up new lines, using the build in Management Software.
@section[Known Problems]
[begin[verbatim]
     No call statistics.
     No guarantee of conformance to PSS.
     No full load sharing.
     No storage of call stats (currently).
     No list/clear of calls to a specific DTE address.
@end[verbatim]
@section[X.25 (1984)]
Amdahl are aware of both the X.25 (1984) specification and the ISO DP8878
document.  There is not a timescale currently for the implementation of the
standards.  They are prepared to discuss the implementation of DP8878 when
an order is placed by the Community.
@section[Academic Community Special Requirements]
They would be prepared to discuss the implementation of specials for the
Community, although they would prefer not to integrate such software into
a 4410.  The prefered vehicle would be the hardware used in the latest
Amdahl PADs.
@section[Product History]
The 4410 has been available since 1980/81 although there has been several
hardware upgrades since that time.  The total sales in the UK has been of
12 units, the customers including W.H. Smith and ICL.  The sales worldwide
have been about 100 units and include one PTT (South Africa).
@section[Maintenance Arrangements]
The maintenance costs are 10% of capital for 'complex' items (those with
discs) and 8% for the rest.  The cover would normally be 9-5 Monday to
Friday excluding public holidays.  The current call out period varies from
2 hours to 6 hours (soon to be reduced to 4 hours) and varies depending
on the locality and is subject to negotiation with the Product Support
and Services division.  There is an established escalation procedure
starting after the engineer has been on site for one hour.
@section[Company Information]
Amdahl is a large US owned company (with Fujitsu holding 46%).  All software
and hardware development is done in the USA (headquarters now in Dallas).
There are 10 people in technical support in the UK.
@section[Confidentiality]
None.
@section[Contact Name]
@flushleft[T. W. Arnold
Amdahl House
112/116 Cricklade Road
Swindon
Wiltshire SN2 6AG
Telephone No 0783 45476]
@section[Summary]
There are a number pf points where Amdahl faial to meet the JNT spec.
In particular the Network Management facilities are surprisingly sparse.

The claims for availability and reliability are more credible than the
competitors, particularly GEC but as the costs of the switches is greater
than the short listed competitors, Amdahl do not represent very good value
for mony for the Community.