GE T1000, Техническое руководство

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Chapter 4
– Functions
GE Reason Switches
108 REASON SWITCHES-TM-EN-3
A peer-to-peer (P2P) delay mechanism calculates the path delay and forwarding
process delay of each component in the network. PTP also allows to be used in an
end-to-end (E2E) delay mechanism, which is similar to the mechanism used in NTP
protocols. In this mechanism, it will be considered all delay between master and
sla
ve as one value, the “path delay” value.
Reason Switches can operate in P2P and E2E modes. Besides, for power system applications, E2E mechanism does not have the
accuracy desired. IEC 61850-90-4 Technical Report recommends using P2P delay mechanism.
12.3 PTP in GE Reason Switches
Reason switches allow to be used in many PTP-aware environments. There are three
main possibilities when using Reason Switches in PTP networks:

Transparent Clock operation;

Boundary Clock operation;

Hybrid Clock operation.
GE Reason Switches has capability to operate both on P2P and E2E delay
mechanisms, which are defined as P2pTransp and E2eTransp device types when the
clock is a TC or p2p and e2e if strictly the port is configured, in BC mode.
If there is the requirement to use BC at the network, Reason Switches may be a
master in a given PTP subdomain. Delay mechanism for the incoming messages from
the Grand Master in the network can be either P2P or E2E delay mechanism.
Reason Switches can operate simultaneously in BC and TC mode, being synchronized
by a Grand Master in a given network and then synchronizing its own PTP
subdomain. Thus, it can operate in HC mode, mixing both modes explained before.
Each Reason Switch can operate as up to 4 ordinary clocks. Thus, the maximum number of instances allowed is 4, defined 0, 1,
2 and 3.
When a clock instance is created, it is able to define which ports will be a part of this
instance freely at the Port List checkboxes.
As explained in the previous sections, PTP protocol allows to be used in layer 2 and 3
protocols. Reason switches have capability to operate in Ethernet frames directly
(layer 2) or UDP transport mechanism (layer 3). This is chosen in the Protocol field at
the configuration window.
Reason Switches allow defining VLAN ID and Priority at the incoming and outgoing
PTP frames. If PTP GMC sends messages with VLAN tag and priority information at
the packet, then it can be configured to be maintained and forwarded by the switch
in a given instance.
Finally, the parameters to be used internally by the switch when computing and
marking the delay at the forwarding PTP frames can also be configured, for thin