S Layer 2 Managed Switch User Manual
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4.6.4 802.1P priority
When 802.1p priority is effective, we can configure different priority Tag (0-7) corresponding to transmission grade (Low, High,
Higher, Highest). If port receives untagged frame, it will assign default priority Tag that configured by this port to this frame
for later process.
Notice: 802.1p priority is only effective under 802.1Q Tag VLAN mode.
4.6.5 802.1p priority remap table
It is a table that original priority Tag remapped to new priority Tag. You can set different mapping relationship between
original priority Tag (0-7) to new priority Tag (0-7). Switch maps frames with different original priority Tag to new priority tag.
Notice:
1.
This mapping table is effective when 802.1p priority remap mode is configured enable.
2.
This mapping table is not effective to data frame that configured default port priority.
4.7 STP
S
supports IEEE802.1D standard STP protocol. STP runs on bridges and switch layer. It follows second level protocol
that compatible with IEEE802.1d. This protocol provides network dynamic redundant switch mechanism. Thus you can deploy
backup line in your network design if STP was used. It will ensure backup line to be closed when main line working normally.
When there is a malfunction occurs in main line, it will active backup line automatically and switch data stream to backup line
to ensure the device working normally.
From this, we can ensure to prevent network loopback when there are redundant paths exist in the network. Network
loopback deadly damages network. Redundant chain as network backup line is very important.
4.7.1 STP realization
STP’s basic theory is transferring a special protocol message (this message is called “configuration message” in IEEE802.1D)
through switches to define network topology. Configuration message contains enough messages to ensure switch completing
calculation of spanning tree.
Content of BPDU shows below:
Below are explanations to each item:
Root switch’s ID: A value that combined with root switch priority and MAC address, this value represents current root switch’s
ID.
Shortest path expense to root:
path expense value of sending switch with BPDU to root switch.
