Network Topology - Lenze SMVector Reference Manual

3.2.6 Network Topology
Given its universal connectivity, an ethernet network may contain varied connection devices including hubs,
switches and routers. Mixing commercial and industrial ethernet networks is possible but care should be
taken to ensure clean data transmission. A large, high performance industrial Ethernet network is best
served by managed switches that permit data control and monitoring capability.
3.2.6.1 Hubs
A hub provides a basic connection between network devices. Each device is connected to one port on
the hub. Any data sent by a device is then sent to all ports (floods) on the hub. The use of hubs is not
recommended for use within control systems due to the increased possibility of collisions. Collisions can
cause delays in data transmission and are best avoided, in severe cases a single node can prevent other
nodes on the same hub (or collision domain) from accessing the network. If using hubs or repeaters you
must ensure that the path variability value and propagation equivalent values are checked. This is beyond
the scope of this manual.
3.2.6.2 Switches
Switches offer a better solution to hubs because after initially learning the addresses of connected devices
the switch will only send data to the port that has the addressed device connected to it. This prevents
excessive traffic. Some managed switches allow the switching of data to be controlled and monitored which
may be of particular importance on large or high performance systems. The word "switch" is sometimes
used interchangeably with the terms scanner, matrix and bridge.
3.2.6.3 Routers
A router is used to communicate between two physical networks (or subnets) and provides some degree of
security by allowing only defined connections between the two networks. A typical use would be connecting
the office and manufacturing networks or connecting a network to an I.S.P (Internet Service Provider). A
router is sometimes known as a gateway as it provides a "gateway" between two networks.
3.2.6.4 Firewalls
A firewall allows separate networks to be connected together similar to a router, however the firewall offers
more security features and control. Typical features include address translation, port filtering, protocol
filtering, URL filtering, port mapping, service attack prevention, monitoring and virus scanning. A firewall is
the preferred method of allowing traffic from a manufacturing network to the business network.
3.2.6.5 VPN (Virtual Private Network)
A VPN is a method of using a non-secure or public network that allows devices to be connected together
as if they were connected on a private network. A typical example would be the connection of two remote
offices such as London and New York. Each office would require a high speed Internet connection and a
Firewall (or VPN device). In order to configure the VPN, encryption keys are exchanged so that both offices
can communicate. The data is then sent across the Internet (or shared network) in an encrypted form,
giving the illusion of a single connected network (speed limitations may apply).
Installation
9 CMVETH01B