830
2.Ethernet Ring (MRPP Ring)
Ring linked Ethernet network topology.
Each ring has two states.
Health state: The whole ring net work physical link is connected.
Break state: one or a few physical link break in ring network
3.nodes
Each switch is named after a node on Ethernet. The node has some types:
Primary node: each ring has a primary node, it is main node to detect and defend.
Transfer node: except for primary node, other nodes are transfer nodes on each
ring.
The node role is determined by user configuration. As shown 1.1, Switch A is
primary node of Ring 1, Switch B. Switch C; Switch D and Switch E are transfer nodes of
Ring 1.
4.Primary port and secondary port
The primary node and transfer node have two ports connecting to Ethernet
separately, one is primary port, and another is secondary port. The role of port is
determined by user configuration.
Primary port and secondary port of primary node
The primary port of primary node is used to send ring health examine packet (hello),
the secondary port is used to receive Hello packet sending from primary node. When the
Ethernet is in health state, the secondary port of primary node blocks other data in logical
and only MRPP packet can pass. When the Ethernet is in break state, the secondary port
of primary node releases block state, and forwards data packets.
there are no difference on function between Primary port and secondary port of
transfer node.
The role of port is determined by user configuration. As shown 1.1, Switch A E1/1 is
primary port, E1/2 is secondary port.
5. Timer
The two timers are used when the primary node sends and receives MRPP protocol
packet: Hello timer and Fail Timer.
Hello timer: define timer of time interval of health examine packet sending by primary
node primary port.
Fail timer: define timer of overtime interval of health examine packet receiving by
primary node primary port. The value of Fail timer must be more than or equal to the 3
times of value of Hello timer.
22.1.2 MRPP Protocol Packet Types
