@make[report]
@device[x2700]
@flushleft[EDINBURGH REGIONAL COMPUTING CENTRE]
@flushleft[COMMUNICATIONS GROUP]
@majorheading[X.25 Packet Switch Survey]
@heading[1st Stage Report]
@section[General]
A total of twenty four manufacturers have been approached to determine what
X.25 packet switch equipment they sold and to do a brief examination into
whether the equipment would be suitable for use in the Academic Community.

Of particular interest were those manufacturers who could provide equipment
of greater connectivity and capacity than the existing GEC 4190 and those who sell very
small switches.
@section[Products]
The following systems we found to be currently marketed:
@begin[verbatim]
         Amdahl:       BBN:         BT:       Camtec:      DCA:
         Dynatech:     GEC:         IPAC:     Memotec:     Motorola:
         Northern Telecom:          Plessey:  SESA:        STC:
         Telefile:    Telematics:   Thorn-Ericsson.
@end[verbatim]
The following companies were approached but do not offer a distinct switch
at this time:
@begin[verbatim]
         CASE:         Logica:                Timeplex (PADs only):
         Jaguar:       Gandalf (PADs only):   Norsk Data.
@end[verbatim]
In addition to the above list XTEC, currently selling PADs, aim to sell a
switch shortly but no details can be obtained yet.  IAL (part of STC/ICL)
sell a switch but it is made by Telematics.

SESA have been approached more than once but have not sent any details.
@section[Basis of Comparison]
The basis of comparison for the alternative systems has been the JNT X.25 switch 
specification, expanded to include a switch with 10 ports (one at 48 kb/s) and a switch
of 100 ports (8 at 48 kb/s).  The prices which have been obtained are for
one-off systems and the throughput figure has been adjusted where necessary
to use the same meaning as in the JNT specification.
@section[Results]
For each of the available products a summary of the main features.  In
addition to these summaries two tables have been included, the
first shows the approximate cost of each system and the second gives a one
line comment on the product.  A summary has not been prepared for either GEC
or Camtec as it was felt that their products were well known within the
Academic Community.
@section[Confidentiality]
The only confidential details in this report one the specific cost of the
Telematics product which were quoted by ICL.
@section[Short List]
Apart from GEC and Camtec who will be used as a 'benchmark' to gauge the
other products it is recommended that the following are investigated in
more detail:-
@begin[enumerate]
Telematics: as they produce an attractive product in all parts of the
size spectrum.

Amdahl: as an alternative large switch.

Dynatech: as a main line supplier of small switches.

Telefile: as an alternative small to medium switch.
@end[enumerate]
@flushright[B. Gilmore
            Oct. 1985.]

@newpage
@majorheading[Summary]
@flushleft[
Amdahl    :  Cost is rather high.

BBN       :  Addressing problems and separate NOC required.

BT        :  Packet rate is very low.

DCA       :  Restriction on number of virtual calls per link.

Dynatech  :  Proposed for short listing.

IPAC      :  Only 9.6 kb/s lines supported.

Memotec   :  Configuration is too restrictive.

Motorola  :  Cost per line is very expensive

Northern
  Telecom :  Basic cost of a switch is too high.

Plessey   :  Performance doesn't reach the JNT spec.

SESA      :  No information received.

SIEMENS   :  Addressing and throughput problems.

STC       :  Initial cost is too high.

Telefile  :  Proposed for short listing.

Telematics:  Proposed for short listing.

Thorn
 -Ericsson:  Cost is too high.]
@newpage
xxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxx
@newpage
@majorheading[Maximum Line Speeds]
@begin[verbatim]
     Amdahl      64 kb/s

     BBN         64 kb/s

     BT          48 kb/s

     DCA         64 kb/s

     DYNATECH    64 kb/s

     IPAC       9.6 kb/s

     MEMOTEC     64 kb/s

     MOTOROLA    72 kb/s

     NT         128 kb/s   

     PLESSEY     64 kb/s

     SIEMENS     64 kb/s

     STC         64 kb/s

     TELEFILE   153 kb/s +

     TELEMATICS  64 kb/s

     THORN
       ERICSSON  64 kb/s
@end[verbatim]
@newpage
@set[section=0]
@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[Configuration Options]
There is a Network Concentrator, called the 4415, which can support up to
40 links.  The main switch called the 4410 Series, can support more than
100 links and its power can be expanded by the addidition of two extra
Processor Units and an optional accelerator unit.
@section[Line Speeds/Interface Options]
The 4415 supports only V24 at speeds up to 19.2 kb/s, the 4410 supports
V24 and V35 at speeds up to 64 kb/s.
@section[Throughput]
The 4415 has a maximum packet rate of 60 packets/sec, the 4410 has a basic
rate of 450 packets/sec upgradable to 1,350 packets/sec.
@section[Costs]
The 4415 configured with 24 links (the first configurable size above 18
links) costs @T{#}18,000.  However, the 4415 requires a Network Administrator
to control it (at a cost of @T{#}36 K).  One would suffice for all
universities although operationally this would not be practicable.  A 4415 
Network Administrator cannot be used to control or manage a 4410.

The 4410 costs a basic @T{#}80,000.  In addition a 9.6 kb/s interface costs
@T{#}1000 with a 48 kb/s interface costing @T{#}2000. 
@begin[verbatim]         
                 4410:  48 lines  -  @T{#}132,000
                       100 lines  -  @T{#}188,000
@end[verbatim]
@section[Multinode Networks]
The switch is designed to fit in a large multinode network and uses a
modified X.25 to communicate between the switches.
@section[Addressing]
Although a line would normally have a single address, other mechanisms are 
available to achieve the desired flexibility.
@section[Network Management]
Comprehensive.
@section[Operator Control]
Comprehensive facilities are available.
@section[Summary]
The 4415 is too expensive because of the need for seperate network
management.

The 4410 would be a feasible 'top end' switch but the cost is rather on
the high side.
@newpage
@set[section=0]
@majorheading[BBN]
@section[General]
BBN offer a range of X.25 networking products that form either entire
networks or networks with value added services such as electronic mail.
The range of products include switches, pads, Network Operation Centres,
service hosts and network authorisation machines.

The switch equipment is based on a microprocessor designed and built by
BBN.  Connection to public data networks is normally done via a Dynatech
gateway machine.

The largest switch has 1/2 Mbyte of memory and can
support 1000 simultaneous calls.  A MTBF of 8000 hours is stated for
the C30.  A maximum packet size of 1024 is supported.
@section[Configuration Options]
Two different switches are supplied, the C30 and the C300.  The C30 will
support a total of 44 links, of which up to 14 can be inter-network links.
The C300 supports up to 64 links of which 14 can be inter-network links.
The minimum size in both cases is 8 lines, expandable in groups of 8.
@section[Line Speeds/Interface Options]
Line speeds of up to 64 kb/s are supported using V24, V35 and RS449.  Up
to 32 links running at speeds greater than 19.2 kb/s can be supported per
switch.
@section[Throughput]
For inter-site traffic (DTE-DTE) the C30 has a maximum throughput of 200
pkts/sec (400 data pkt), the C300 has a throughput of 450 pkts/sec.
For DTE-trunk traffic the throughput is halved.
@section[Costs]
@begin[verbatim]
            The C30 costs from @T{#}60    -  80K
            The C300 costs from @T{#}80   - 100K
@end[verbatim]
@section[Multinode Networks]
The switches are designed to operate in a multinode network and they use
a private datagram protocol between the switches.
@section[Addressing/Routing]
There are two forms of address, a physical address and a logical address.
The logical address can be used to form link groups or give a particular
DTE a range of addresses over multiple switches BBN have chosen to
use the 5th octet of the X.121 address but to distinguish between 
the two forms.  This would mean conflict with our current addressing strategy.

Routing is achieved by dynamic load balancing on a per packet basis.
@section[Network Management]
Network Management is performed by a Network Operations Centre.
@section[Operator Control]
Operator control is also performed by the NOC and the facilities appear to
be fairly comprehensive.
@section[Conection to PSS]
BBN recommend the Dynatech 'Adress Translator' to couple BBN and Public
Data Networks.
@section[Summary]
The need for a NOC, the restriction in addressing, the low packet throughput
coupled with the problems of attaching to Public Data Networks rule out the
use of this equipment for campus networks.
@newpage
@set[section=0]
@majorheading[B.T.]
@section[General]
BT sell small X.25 switches under the name @b[Packet NetMux]; this is a
Z80 based system with a maximum 40 Kbytes of store.
@section[Configuration Options]
Packet NetMux can be configured with up to 7 X.25 links.
@section[Line Speeds/Interface Options]
Line Speeds of up to 48 kb/s can be supported (at least on a hardware level)
supporting V24 or V35.
@section[Throughput]
The maximum packet rate is 16 packets/sec.  When BT were asked about 48 kb/s
support, the response was that it could attach at this speed but not support
the potential packet rate.
@section[Costs]
Costs vary from @T{#}4,480 for 2 links to @T{#}5,605 for seven links.
@section[Multinode Networks]
Can be done using X.25.
@section[Known Problems]
Apart from the inadequate packet throughput, the following points fail to
meet the JNT spec.
@begin[enumerate]
Packet and Window size are fixed at 2 and 128.

Addressing/Routing is extremely inflexible.

All configuration details, including addressing, timing
and DTE/DCE are fixed and can only be changed by BT.
@end[enumerate]
@section[Summary]
With the above problems Packet NetMux is not suitable for use in the
Academic Community.

@newpage
@set[section=0]
@majorheading[DCA]
@section[General]
DCA provide an X.25 interface to their DCA System 355 Master Network
Processor which is primarily aimed at the terminal switching market.
This equipment may be used as a switch and PAD facilities are also provided.

The X.25 interface is supported on a sepera card and with its own micro
processor that fits into a card slot of a system 355.  There is a major
drawback in that any one card can only support 32 virtual calls.  A maximum
packet size of 2048 bytes is supported but there is no negotiation of packet
or window size allowed.
@section[Configuration Options]
A maximum of 44 X.25 lines can be supported.
@section[Line Speeds/Interface Options]
Two options are available, first a card that drives a single 9.6 kb/s
line and secondly a new pair of cards that drive 2 lines both at speeds up
to 64 kb/s.

A maximum speed of 19.2 kb/s can be supported using V24 and up to 64 kb/s
using V35.
@section[Throughput]
It is claimed each X.25 card can handle the maximum throughput that a
19.2 kb/s link can produce and that there is no limitation on carrying
this across the lines when generated by all the ports.  There is no
evidence that this has ever been tried out.
@section[Costs]
A basic DCA 355 costs @T{#}6,925 (including X.25 Software).  The cost
of each 9.6 kb/s port is then @T{#}1,448 and pair of 64 kb/s ports cost
@T{#}3,935.  Thus:
@begin{verbatim}
                  10 ports - @T{#}22,444
                  18 ports - @T{#}37,968
@end[verbatim]
@section[Miltinode Networks]
System 355s uses an internal protocol when interconnected.  For large
networks, DCA would recommend Telematics but their systems have not been
properly integrated with the Telematics equipment.
@section[Addressing]
Either individual addresses or a 'wild card' system can be used.
@section[Network Management]
There are two packages available using an IBM PC/XT or AT which can
provide alarm logging and a colour graphics package.
@section[Operator Control]
Only a pre-defined terminal, ie. one that is attached to a System 355, can be
used for switch control.
@section[Summary]
The limit of only 32 virtual calls per X.25 card, the lack of packet and window
size negotiation, and the rather high price per port make this equipment too
constrained for use as general packet
switches.
@newpage
@set[section=0]
@majorheading[DYNATECH]
@section[General]
Dynatech sell a range of X.25 equipment including PADs, switches and a
Gateway Address Translator and a Network Control Centre.  The switch is called @b[Multi Switch X.25] and
has been certified for use with most of the public data networks.  It is
based on a Z80 with 248 Kbyts of RAM.
@section[Configuration Options]
The Multi Switch comes in two types, the Model 8 and the Model 12 High
Speed supporting from 4 links to either 8 (Model 8) or 12 (Model 12) links maximum.
@section[Line Speeds/Interface Options]
The Model 8 supports a maximum speed of only 9.6 kb/s, the Model 12
supports speeds of up to 64 kb/s, which may be internally clocked up to
56 kb/s.  V24, V35 and X.21 are available.
@section[Throughput]
A packet throughput of 100 data packets/sec is quoted for the Model 12.
@section[Costs]
The Model 8 costs @T{#}3,665 for 4 lines and @T{#}5,669 for 8 lines.
The Model 12 costs @T{#}17,200 for 4 lines with an additional @T{#}2,297
per 2 lines.

Therefore, for a Model 12:- @centre[10 links -  @T{#}24,091]
@section[Multinode Networks]
The Dynatech can operate as a concentrator type switch using X.25 to
communicate with the other nodes and is capable of load sharing across
multiple lines.
@section[Addressing]
Appears flexible with the ability to use single addresses and/or ranges
of addresses.
@section[Network Management]
Any Dynatech switch can be interrogated by any network terminal (password
protected) to determine basic data such as:- status of links, number of
calls on each link, number of users on the line.

Dynatech also sell a @b['Network Control Centre'] based on an IBM XT
connected to an asynchronous PAD port.  This is all done on a 'passive'
basis, ie. it is polled by the operator/NCC and it does not appear
possible to obtain details of calls made or counts of various packet types.
@section{Operator Control}
The feature mentioned above can be used to control a switch remotely.
Most features in the JNT spec are included with the exception of the
ability to 'clear a call to a selected DTE address'.
@section[Summary]
An interesting switch which could be used as a X.25 concentrator for
a larger switch.  Although the cost per line is rather high, it is
worth investigating this switch in more detail.


@newpage
@set[section=0]
@majorheading[IPAC]
@section[General]
IPAC sell the COMPAC VCX which is an X.25 switch forming a part of a set
of X.25 products including PADs and a Network Management Centre.  The
COMPAC VCX is of French design and manufacture and is based on a Z80
processor with 128 Kbytes of memory.  A total of 80 simultaneous calls
can be supported.
@section[Configuration Options]
Two switches are produced, the CP1 supporting 8 lines and the CP1S
supporting 16 lines.
@section[Line Speeds/Interface Options]
Both switches only support a maximum line speed of 9.6 kb/s.
@section[Throughput]
Maximum packet rates of 80 and 160 packets/sec are quoted for the two types.
@section[Costs]
The cost of the 8 line switch is @T{#}8K and the 16 line switch @T{#}15,300.
@section[Known Problems]
The COMPAC VCX does not meet the JNT spec in a number of key points, they
are:-
@begin[itemize]
Only 9.6 kb/s supported.

No Fast Select.

Can only use LCGN-4.

Severe Addressing constraints.
@end[itemize]
@section[Summary]
The above problems must rule out this switch, IPAC say that there is a new
version on the way - the @b['COMPAC NPX'] but there are no technical details
available yet.

The cost of the NPX will be: 12 ports @T{#}24,400
@newpage
@set[section=0]
@majorheading[MEMOTEC]
@section[General]
Memotec switches, as marketed by Drake Systems are part of a range of X.25
products including PADs and a Network Control Centre.  The range is called
@b[MPAC] and the switches are certified for use on a wide variety of public
data networks.  The equipment is manufactured in Canada.
@section[Configuration Options]
The switch comes in two types, the @b[MPAC 2500] which supports up to 8 lines
and the @b[MPAC SP/8564] which supports 4 high speed lines.
@section[Line Speeds/Interface Options]
The 8 line @b[MPAC 2500] has a maximum speed on all ports of only 9.6 kb/s. 
The @b[SP/8564] has a maximum speed of 64 kb/s and supports V24, X21 and V35 (and RS449?).
@section[Throughput]
Unknown.
@section[Costs]
The 8 low speed 2500 costs @T{#}6,000, the 4 channel SP/8564 costs @T{#}9,197.

Cost per line (4 lines!) is @T{#}2,300
@section[Summary]
It has proved very difficult to obtain adequate information on this
product but the fairly high line cost coupled with the constrained
configurations do not justify further investigation.

Memotec are also offering a new box, the MPAC MP/8000, which is combination of
switch and PAD.  Up to 12 X.25 lines running at 64 kc/s can be supported
at a cost of @T{#}15,093 for 12 lines.  No further information could be
obtained from Memotec.
@newpage
@set[section=0]
@majorheading[MOTOROLA]
@section[General]
Motorola offer a M68000-based X.25 switch called the @b['Intelligent X.25
Processor' (IXP)].  A maximum store size of 384 Kbytes is allowed and it
is stated that up to 1000 virtual calls can be supported.
@section[Configuration Options]
Two types of switches are offered, a standard, and a high performance, both
types can support from 2 to 32 physical links.
@section[Line Speeds/Interface Options]
The 'standard' switch supports only V24 interfaces up to a maximum speed
of 19.2 kb/s.  The high performance switch supports line speeds to 72 kb/s
using V24, V21, RS422 or V35 in a flexible fashion.
@section[Throughput]
800 pkts/sec is claimed for the high performance switch.
@section[Costs]
The basic cost of a high performance switch is @T[#]15,500 configured with
2 ports.  There is then an additional cost of @T[#]2,000 per port board each
of which supports two links.  There is an additional cost of @T[#]100-@T[#]250 for the physical interface.

This gives the following costs:-

@centre[10 ports @T[#]26,800;  18 ports @T{#}33,600]
@section[Multinode Networks]
Motorola switches will work as part of a multinode network using 'simple'
X.25 between the nodes.
@section[Addressing/Routing]
Addressing is handled by conversion to names - it appears flexible but obscure.
@section[Network Management]
There is no disc attached to the system, so there is no collection of
statistics.  However, statistics, including details of calls etc., can be
directed to a network 'console', consequently a micro, or similar, could
be attached to collect, time stamp and present statistics.
@section[Operator Control]
Operator control can be either from the console attached to the switch or
from any network terminal (password protected).  The level of control provided from this
console appears to be fairly comprehensive and meets most of the requirements
in the JNT spec, including the ability to list all calls, with addresses, to
a particular DTE.
@section{Known Problems}
The switch supports a maximum packet size of only 128.
@section[Other Points]
It has proved extremely difficult to get a proper technical manual and
consequently it has not been possible to check a number of points in detail.
@section[Summary]
This is a fairly typical small switch, even though it does go up to 32 links,
with the typical disadvantages of small switches, ie. lack of network
management and proper control of the switch.  When this is coupled with a
high cost per line (@T[#]2,250) it does not appear to be worth pursuing.
@newpage
@set[section=0]
@majorheading[Northern Telecom]
@section[General]
Northern Telecom sell a range of network products including switches, PADs
and a network control system.  The system is used as the basis for DATAPAC
in Canada and DATEX-P in Germany. The switches are based on multi 16 bit
processors.  512 kbytes of common memory is supported, with each processor
having additional private memory, no guide is
given for the maximum number of calls although up to 1200 subscribers can
be connected to a single switch.
@section[Configuration Options]
Northern Telecom sell a concentrator, the SL rapid, which can support up to
208 low speed lines and uses a maximum of 73 kb/s speed line to connect back to a main
switch.

The main switch, called the SL10 can be configured with up to 10 line
modules, or each line module can be replaced with three trunk modules
supporting links to other SL10s.  

Each line module can support up to 120 lines at 9.6 kb/s or 4 high speed
lines (max 64 kb/s).

With 3 trunk links, and 8 links at 64 kb/s, the SL10 could support an
additional 840 9.6 kb/s links.
@subsection[Line Speeds/Interface Options]
The SL10 supports V24 and V35 at speeds up to 64 kb/s.
A trunk link to another SL10 can be run at 128 kb/s.
@section[Throughput]
The SL10 can support up to 1500 packets/sec (quoted at 750 user data
pkts/sec).
@section[Costs]
A minimum SL10 switch system starts at @T{#}150,000.
@section[Multinode Networks]
The SL10 is designed to work in a multi node network and uses an internal
datagram protocol to communicate between the switches.
@section[Addressing]
The SL10 expects to use X75 to communicate with external networks and the addressing does
not appear to be flexible enough to be used in conjunction with the existing
equipment.
@subsection[Network Management & Operator Control]
This is achieved in an extremely powerful manner by the separate Network
Control Centre.
@section[Summary]
The need for a Network Control Centre, combined with possible addressing
problems and with the extremely high basic cost rules out this option.
@newpage
@set[section=0]
@majorheading[PLESSEY]
@section[General]
Plessey provide X.25 products that are used in large Public Data Networks,
eg. PSS, and for computer networks such as the Midland Bank.  The largest
switch, the TP4000 is multi-microprocessor-based with a store size of
64-256 Kbyte.  The smaller, concentrator, switch the Series 2500 is based
on an Intel 8086 with up to 256 Kbytes of memory.
@section[Configuration Options]
The largest switch, the TP4000 supports up to 250 ports (made up out of
36 line processing cards each with 8 lines).

The concentrator switch, the Series 2500 comes in three different sizes
and performances, a 16, 24 and 48 port versions.
@section[Line Speeds/Interface Options]
Both types support line speeds of up to 64 kb/s using V24 or V35.
@section[Throughput]
The TP4000 has a disappointing top packet rate of only 450 packets/sec
(quoted as 225 data packets/sec).  This is on DTE/DTE calls, the
switch is quoted at being able to switch 2000 packet/sec on inter-switch
links.

The Series 2500 had 3 different rates.
@begin[verbatim]         
                    16 ports  -  60 packets/sec
                    24 ports  -  90 packets/sec
                    48 ports  - 180 packets/sec
@end[verbatim]
It can be seen from this that Plessey cannot match the JNT spec, even at
48 ports, for performance.
@section[Costs]
The TP4000 costs from @T{#}100,000 - @T{#}200,000.
@begin[verbatim]    48 ports - @T{#}150,000
@end[verbatim]
The Series 2500 costs:-
@begin[verbatim]
                    16 ports - @T{#}13,000
                    24 ports - @T{#}17,000
                    48 ports - @T{#}30,000
@end[verbatim]
@section[Multinode Networks]
System has been produced to handle massive networks.
@section[Addressing]
Apparently meets the JNT spec with the restriction that a Zone system must
be used between groups of nodes, although not between members of the group.
@section[Network Management]
Extremely powerful but requires to run on a Prime.  Plessey are, however,
going to produce a micro-based Network Operation Centre for use in smaller networks.
@section[Operator Control]
The quality of control is considerably better than that of the GEC switch.
@section[Summary]
The performance of the switches is disappointingly low, the biggest switch not
meeting the JNT spec and this coupled with the extremely high cost rules
this equipment out.
@newpage
@set[section=0]
@majorheading[SIEMENS]
@section[General]
Siemens produce a range of equipment for X.25 packet networking called the
System EDX-P including switches, concentrators, PADs and Network Control Centre.
In the U.K., the system is marketed by Databit Ltd who are owned by Siemens.
Packet sizes of up to 256 bytes are
supported.
@section[Configuration Options]
The concentrator, the ANP2530 - which can act as a switch in its own right
with additional software - supports between 8 and 128 links.  The main switch,
the System EDX-P can support up to 1008 links.
@section[Line Speeds/Interface Options]
The concentrator supports line speeds of up to 19.2 kb/s and network links
at up to 64 kb/s.  The EDX-P supports links at up to 64 kb/s.
@section[Throughput]
The switch is rated at 700/900 pkts/sec.  It handles X.75 more
efficiently than X.25.
@section[Costs]
ANP 2530 costs approximately @T{#}20,000-@T{#}25,000 (a 32 line @T{#}19,200 -
@T{#}25,600).

A 100 line EDX-P costs approximately @T{#}100,000.
@section[Multinode Networks]
The EDX-P has been designed to work in a multinode network and uses a 
variant of X.75 to communicate between the nodes.
@section[Addressing]
Databit have requested information from Siemens over the use of
addressing.
@section[Network Management & Operator Control]
Siemens use a Network Control Centre to down line load the ANP2520, receive
the call statistics etc., and to control the network.  It is possible to integrate
the NCC into a System EDX-P, which then can also control any EDX-Ps in
the network.
@section[Summary]
There remains the question of addressing to be resolved and it appears to
have a disappointingly low throughput.
@newpage
@set[section=0]
@majorheading[STC]
@section[General]
STC offer the DPS 1500 Packet Switching System.  The product line consists
of switches, PADs and a Network Operation and Management Centre.

The switches are formed from two pieces of equipment, the Packet Data
Satellite (PDS) and the Packet Switching Exchange (PSE).  The PDS handles 
the user equipment while the PSE performs switching and routing.  Both
pieces of equipment are based on a high speed bus supporting multi 
micro-processors.  The hardware MTBF for a PDS and PSE are quoted at 4.93 years
and 1.88 years.  A maximum packet size of 1024 bytes is supported.
@section[Configuration Options]
The minimum network consists of a Packet Data Satellite with two Line
Access Modules and a Packet Switch Exchange with two Line Access Modules.
Each Line Access Module (on the PDS) can support up to 16 access lines with
an average aggregate throughput of 32 kb/s full duplex.  Consequently, the
smallest switch pair can handle 32 lines (at 32 kb/s) or 2 lines at 48 kb/s
and 30 lines at 37 kb/s.  One or more of these lines need to be connected
to the PSE.

This small switch configuration can be expanded to 16 LAMs or a maximum of
1000 links.  The maximum numbert of X.25 links for a whole network is
175,000 links.
@section[Line Speeds/Interface Options]
Line speeds of up to 64 kb/s using V24, V11 or V35 are supported.
@section[Throughput]
A Packet Processing Module (PPM) is used in either the PDS or the PSE.  A
PPM will support 150 pkts/sec.  Up to 100 PPMs can be installed in a switch,
giving a total throughput of 6,000 packets/sec.
@section[Costs]
The smallest configuration (30- 32 links) costs @I{#}140,000.
@section[Multinode Networks]
The system has been designed as a large multinode network and uses the
'netgram' - an internal datagram protocol to communicate between switches.
@section[Addressing/Routing]
There appears to be flexibility in the use of X.121 addressing, however,
the main inter-network link is done by X.75 and the DPS1500 may not support
DTE interfaces.

Hunt groups, including support for an address across multiple PDS's are available.
@section[Network Management]
Network Management is performed by a Network Operation and Management Centre
which can be either a stand alone PDP11/24 (or 11/44) or can be integrated
within the PSE.
@section[Operator Control]
Very full operation control from the NOMC has been provided.
@section[Summary]
The DPS1500 appears to be too expensive for further consideration for
individual universities.
@newpage
@set[section=0]
@majorheading[TELEFILE]
@section[General]
Telefile is a small company (owned by a US parent) producing a switch called
TelePAC.  This is a M68000-based switch using the standard VME bus.  The
basic system has 192 Kbytes of store (soon to be expanded to 750 Kbytes).
It is claimed that 100 virtual calls can be supported.  About 100 systems
have been installed world-wide in the last 3 years.  TelePAC units will be able  
to be joined together using a DMA interface.  This interface could also be used to
connect to a user-programmed processor supporting a UNIX-compatible system
for use as a Gateway or other such protocol converter.  TelePAC is certified for
use on most public networks.
@section[Configuration]
One TelePAC can support up to 30 lines, a MegaPAC will be formed by joining
up to 16 TelePACs together using DMA channels.
@section[Line Speeds/Interface Options]
Line speeds of up to 153 kb/s can be supported using V24, V10/11, V35 or
X21.
@section[Throughput]
A throughput of greater than 1162 packets/sec is claimed.
@section[Costs]
10 ports @T{#}11,000;  18 ports @T{#}12,500;  48 ports @T{#}35,500
@section[Multinode Networks]
The switch will work in either the MegaPAC situation or as a
multinode network. Load sharing is performed across multiple links.
X.25 is used between the nodes.
@section[Addressing/Routing]
The method used for routing is different from most others.  All addresses
are turned into 'names' and routing etc is done on the basis of these names.
Single addresses or ranges can be used though as it uses 'wild cards' (eg.
50** to match a range 5000-5099). Complete flexibility on ranges is missing.
@section[Network Management]
The basic switch does not include a disc, although most of the required
information can be routed to a network 'port'.  This area in particular
would need enhancing for the switch to be acceptable.
@section[Operator Control]
The operator control facilities appears to be flexible, with the ability to
use any (password protected) terminal for the control.  Lines can be reconfigured
without requiring a reload of the entire switch.
@section[Summary]
Although TelePAC does not support all of the Network Management features required
in the JNT spec, the cost, power and flexibility of the architecture warrant
a closer look.
@newpage
@set[section=0]
@majorheading[TELEMATICS]
@section[General]
Telematics offer a range of X.25 networking products called the Net 25
Product Family including concentrator switches, primary switches, backbone
switches, PADs and supervisory nodes.  The equipment is based on Motorola
M68000s and the largest node has a store size of 4 Mbytes expandable up to
8 Mbytes.  A maximum of 1500 simultaneous calls can be supported on the largest
node.  The equipment is sold in the UK by Telematics and also by ICL and
other companies including IAL who sell it under their own label.  Telematics
is certified for use on most public data networks.  The maximum packet size
supported is 1024 bytes.

@section[Configuration Options]
The switches are sold in a wide variety of options starting at 16 lines
expandable up to 1024 lines on the largest switch.
@section[Line Speeds/Interface Options]
Up to 64 kb/s is supported, even on the smallest switch, to interface
standards V24, V35 and X21.
@section[Throughput]
Throughput varies from 100 packets/sec (quoted as 50 data packets/sec)
at the lowest end, expandable by adding both a communications accelerator
and up to two additional general purpose processors to give a maximum
throughput of 1600 packet/sec (quoted as 800 data packet/sec).
@section[Costs]
@begin[verbatim]
    10 line  100 packet/sec  @T{#}12K  (when used in conjunction
                                         with a bigger switch)
    18 line  100 packet/sec  @T{#}14K  (when used in conjunction
                                         with a bigger switch)
    18 line  200 packet/sec  @T{#}40K  (smallest stand alone switch)
    
    48 line  800 packet/sec  @T{#}83K

   100 line 1600 packet/sec  @T{#}113K
@end[verbatim]@b[NOTE: These prices are from ICL and are confidential.]
@section[Multi-node Networks]
Designed for use in this environment, Telematics use a non-X.25 protocol
for inter-switch communication.
@section[Addressing]
Flexible control over X121 addressing is allowed, full compliance with 
the JNT spec still has to be established.
@section[Network management]
Appears to be fairly comprehensive.  It is noted that the smallest switch
requires to be linked up with a 'standard' switch for the purpose of
network management.

There is a specific network management machine, based on the same
architecture, but this function can also be integrated into a standard switch.
@section[Operator Control]
Appears to be very flexible, meets and exceeds most of the points in the
JNT spec (the possible exception is the clearing of a particular call).
Any network terminal, password protected, may also be used.  Line configuration, and
even the replacement of channel boards can be performed on a live system. 
@section[Other Points]
An extremely flexible system with the ability to add user programs, eg.
for YB-ISO conversion, has been constructed.  There is also an optional
'protection module' for protecting switches from code added by the user.
@section[Known Problems]
Fast Select is not currently supported, but a release of software which includes
Fast Select, is planned for November 1985.
@section[X.25 (1984)]
This is expected to be ready early in 1986.
@section[Summary]
This series is extremely cost effective, has modules right across the
connection spectrum, has extremely easy upgrade paths for performance
expansion and has the ability for the Community to add user designed software.

As an extremely attractive alternative to GEC it is worth considering in
Stage 2.
@newpage
@set[section=0]
@majorheading[Thorn Ericsson]
@section[General]
Thorn Ericsson offer ERIPAX which is a networking system comprising switch,
PADs and network management stations.  The equipment is based on a flexible
mixture of Motorola 68000s and 6809s supporting a maximum store size of 8
megabytes.
@section[Configuration Options]
Up to 32 'Computer Modules' can be built into a single node.  Each Computer
Module can support between 2 and 8 physical links giving a maximum usable
configuration of over 200 links.
@section[Line Speeds Interface Options]
The ERIPAX supports V24 to 19.2 kb/s and V35 at speeds up to 64 KB/s.  X.21 and
G703 are also supported.
@section[Throughput]
A single 'Computer Module' can support 200 packets/sec (quoted as 100 data
pkts/sec).  Based on this a maximum of 1000 packets/sec (500 data packets
/sec) is claimed for an entire node, although it can be higher if a
particular system is configured carefully.
@section[Costs]
@begin[verbatim]
                   10 ports - #140,000
                  100 ports - #500,000
@end[verbatim]
A new release of hardware is due at the end of the year which will reduce
the cost of the 100 port switch to @T{#}300,000 approximately.
@section[Multinode Networks]
A modified form of X.75 is used between nodes of a network and X.75 is
recommended for use between different networks.
@section[Addressing]
A flexible addressing scheme is available with the ability to have ranges
based on a match of less than 12 digits in an address.  However, only one address or one 
range is allowed on a single link.  Hunt groups are available but they do
@u[not] load share.
@section[Network Management]
Network Management can be implemented on a stand-alone machine or integrated
into a node.
@section[Operator Control]
Operator control must be done by a terminal attached to one of the nodes.
@section[Summary]
The limitations in the addressing structure coupled with the high cost
rule out this equipment.