The main benefits of Freeway is that it supplies better scalability and
reliability than the TCP distribution system supplied by Remote Client and
Server. It is also easier to configure. However, this benefit has to be offset
by the cost of hardware setup. Generally, it is only worth installing this
system in larger networks. Freeway servers advertise the existence of Dataworks Enterprise sources and make
their data available to Freeway clients using UDP IP multicast (or by
configuration broadcast). Freeway clients are "aware" of all the instances of a
particular Dataworks Enterprise source within the network and will load balance
their use of these resources. Consequently, the network is considerable more
scaleable than the standard Remote Client/Server network. Additionally, clients
dynamically reconfigure themselves as servers come online or go offline. In essence, Freeway is a "bus" technology. A number of hosts are connected to a
private, dedicated network, typically using an Ethernet switch, either as
Freeway clients or Freeway servers or both. Consequently, each machine in
question has an additional network interface dedicated to the Freeway network.
This network is known as the "backbone" and all Freeway communication happen
using it. The network-level communications are integrated into a module is known as the
"Freeway Broker". For maintenance purposes it is possible to "sniff" the Broker
communications using a separate program called "Sniffer" supplied as part of
the core distribution. The broker is responsible for detecting the presence of
peers, packet sequencing and retransmission, fragmentation and so on. At a higher level is the Freeway module itself. This incorporates by the client
and server code in the same binary. This eases installation and configuration
issues. The Freeway server code consists of a Dataworks Enterprise RTClient that it uses
to send requests upstream, and the interface to the broker code for
communicating to the Freeway network. Freeway servers are responsible for
"advertising" the sources that they are making available to Freeway clients,
which they do by sending "SourceSet" messages when a client connects and
updates when changes are made to their source tables. The Freeway client code consists of a Dataworks Enterprise RTServer for
connection to downstream "devices" and the code required to select and use
Freeway servers as reported by the broker. All Freeway clients maintain lists
of peers using an ordering scheme which is the same for all clients. Freeway
clients load balance between servers using a hashing algorithm. The hash is
invariant for any request on any client machine. Consequently, two Freeway
clients requesting the same information will request this data from the same
Freeway server. So if two Freeway clients are requesting the same 40K
instruments from two Freeway Servers, the total number of requests at each
server will be approximately 20K. Moreover, the update streams for all these
instruments are consolidated, so it does not matter how many clients are
attached to the network. This is how the system achieves scalability. Freeway clients and servers typically also run Remote Servers and Clients
respectively amking the Freeway "service" available externally although there
is no technical reason why the service cannot be accessed directly from the
Freeway network. First Introduced in beta form in Release 2.0.0.147. None. Freeway uses a standard configuration file that is documented. As far as
possible, the Freeway module is "self configuring". When the module starts up,
it connects to the multicast bus and gets most of its configuration information
from the network. However, in order to achieve this some configuration may have
to be made locally. Typically, the only real configuration required is whether the module is to be
run as a Client, a Server or Both. Ocassionally, the IP subnet to use also
needs to be configured. It defaults to 10.0.0.0. This module does not intrinsically provide sources, except for the management
sources used by the Source Monitor for statistics collection. These management
sources are, by default, turned off. For a Freeway client, the management
sources is called: For the server it is: To use these sources, request the instrument "CATALOGUE". This will return a
record containing a list of other records which can be requested and a list of
commands that can be executed by the component. The actual content of this
record depends on the module in question and is subject to change from time to
time. None.Freeway
Freeway is the name of Dataworks Enterprise' multicast
distribution system.
Detail
History
Dependencies
Configuration
Sources
Freeway.[config]@[machine_name]
Freeway.[config]@[machine_name]
Known Problems