Amer Networks SS3GR24i - Manual (Page 29)

SS3GR24i/SS3GR48i Layer3 Stackable Gigabit Switch User’s Guide
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A P2P port is also capable of rapid transition. P2P ports may be
used to connect to other bridges. Under RSTP, all ports operating
P2P Port
The edge port is a configurable designation used for a port that is
directly connected to a segment where a loop cannot be created. An
example would be a port connected directly to a single workstation.
Ports that are designated as edge ports transition to a forwarding
state immediately, without going through the listening and
learning states. An edge port loses its status if it receives a BPDU
packet, immediately becoming a normal spanning tree port.
Edge Port
RSTP is capable of more rapid transition to a forwarding state – it
no longer relies on timer configurations – RSTP compliant bridges
are sensitive to feedback from other RSTP compliant bridge links.
Ports do not need to wait for the topology to stabilize before
transitioning to a forwarding state. In order to allow this rapid
transition, the protocol introduces two new variables: the edge port
and the point-to-point (P2P) port.
Both protocols calculate a stable topology in the same way. Every
segment will have a single path to the root bridge. All bridges
listen for BPDU packets. However, BPDU packets are sent more
frequently – with every Hello packet. BPDU packets are sent even
if a BPDU packet was not received. Therefore, each link between
bridges are sensitive to the status of the link. Ultimately this
difference results in faster detection of failed links, and thus faster
topology adjustment. A drawback of 802.1d is this absence of
immediate feedback from adjacent bridges.
state Discarding . In either case, ports do not forward packets; in
the STP port transition states disabled, blocking or listening or in
the RSTP port state discarding there is no functional difference,
the port is not active in the network topology. The table below
compares how the two protocols differ regarding the port state
transition.