30. Tunnelling
ROX™ v2.2 User Guide
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RuggedBackbone™ RX5000
Secondary
Synopsis: IPv4 address in dotted-decimal notation
Secondary WINS server.
30.3. Layer 2 Tunnelling
RuggedBackbone™ is capable of extending the range of services that communicate solely via Layer 2
protocols (i.e. at the level of Ethernet) by tunneling them over routed IP networks. The Layer 2 Tunnel
Daemon supports the IEC61850 GOOSE protocol as well as a generic mechanism for tunneling by
Ethernet type.
You can configure GOOSE tunnels and generic Layer 2 tunnels and also view tunnel status and
statistics.
30.3.1. IEC61850 GOOSE Fundamentals
IEC61850 is an international standard for substation automation. It is a part of the International
Electrotechnical Commission’s (IEC) Technical Committee 57 (TC57) architecture for electric power
systems. An important feature of IEC61850 is the fast transfer of event data. Transfers of Generic
Substation Events (GSEs) are accomplished through the GOOSE (Generic Object Oriented Substation
Event) protocol.
IEC61850 uses Layer 2 multicast frames to distribute its messages and hence is incapable of operating
outside of a switched Ethernet Network. The GOOSE tunnel feature provides a capability to bridge
GOOSE frames over a WAN.
GOOSE tunnels provide the following features:
• GOOSE traffic is bridged over the WAN via UDP/IP.
• One GOOSE traffic source can be mapped to multiple remote router Ethernet interfaces in mesh
fashion.
• To reduce bandwidth consumption, GOOSE daemons may be located at each of the “legs” and at the
center of a star network. The centrally located daemon will accept GOOSE packets and re-distribute
them.
• Statistics report availability of remote GOOSE daemons, packet counts and Round Trip Time (RTT)
for each remote daemon.
• When Virtual Router Redundancy Protocol (VRRP) is employed, GOOSE transport is improved by
sending redundant GOOSE packets from each VRRP gateway.
• You can enable GOOSE forwarding by configuring a generic Layer 2 tunnel. When configured,
RuggedBackbone™ listens for GOOSE packets on one VLAN and forwards them to another VLAN.
30.3.1.1. GOOSE Tunnel Implementation Details
The GOOSE protocol is supported by the Layer 2 Tunnel Daemon. The daemon listens to configured
Ethernet interfaces and to the network itself (i.e. for tunnel connections from other daemon instances)
on a configurable UDP port.
The Media Access Control (MAC) destination address of frames received from Ethernet is inspected
in order to determine which GOOSE group they are in. The frames are then encapsulated in network
headers and forwarded (with MAC source and destination addresses intact) to the network as GOOSE
packets.
IEC61850 recommends that the MAC destination address should be in the range 01:0c:cd:01:00:00 to
01:0c:cd:01:01:ff.