Afar AR24027, Руководство оператора

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AR24027 Operator’s Manual
2-8
is the synchronization source. In fact any gateway can be added or dropped without affecting the
cycle timers of the remaining gateways.
You must configure the three left radios as the “hub” for their RF links. Each of these three radios
detects the presence of the respective gateway, which becomes the source of its heartbeat over the
Ethernet. In this way, all three radios run their cycle times synchronized and following timeline A in
the figure.
The middle site in the figure illustrates another way in which the gateways participate in the cycle
synchronization. At this site radio 5 is a “remote” with its cycle synchronized to radio 2 across the
RF link. Radio 5 therefore becomes the source of the heartbeat at this site. It sends heartbeat packets
over the Ethernet, which synchronize the cycle timer of gateway 5. As shown in the figure you must
connect gateway 5 and 6 SYNC ports together and configure their tdd sync-mode to
auto . In this
mode the gateways propagate the heartbeat between the Ethernet WAN port and the SYNC port.
Gateway 5, which receives heartbeat packets from the radio, drives the SYNC port. Gateway 6
synchronizes its cycle timer to the SYNC port and sends heartbeat packets to radio 6. In this fashion
the two co-located radios at this site have their cycle times synchronized, following timeline B. At
this same site you could have more pairs of gateways and radios. You would connect the SYNC lines
of all the gateways together and configure their tdd sync-mode to auto.
At the sites where there is a single radio and gateway you should set the gateway tdd sync-mode to
off . Since there are no co-located radios this setting turns off the generation of heartbeat packets
which are unnecessary.
2.4 Ethernet Bridging
2.4.1 Self-learning bridging
The radio operates the Ethernet port in a self-learning bridge mode. It configures the port in
promiscuous mode, i.e., it examines all the Ethernet packets that are flowing in the local LAN. Since
these Ethernet packets contain a
source and destination address, the radio quickly learns the
addresses of all the local stations connected to the LAN (all the source addresses of packets flowing
in the LAN are local).
As a radio receives packets over RF it also learns the addresses of stations that can be reached across
that RF link. For a hub radio in a PmP topology, the radio keeps track of which addresses are
associated with each remote.
With this information on hand, each radio examines the destination address of every Ethernet packet
in the local LAN and makes one of the following decisions:
1. If the destination address is for a local station, discard the packet.
2. If the destination address is associated with a remote radio, queue that packet to be forwarded to
that remote radio. Note that for a PmP topology, the hub radio keeps multiple output queues, one
per remote radio.
3. If the station address is unknown or is a broadcast send the packet to all the remote radios.
Each device has capacity to store 500 entries in its Ethernet table. Entries are erased after a certain
amount of time to allow for stations to be moved between LANs and not show up in two distinct