E-Series Spanning Tree (Ieee 802.1D) - Cisco ONS 15454 SDH Configuration Manual

E-Series Spanning Tree (IEEE 802.1D)

Figure 23-16
No priority
ONS node maps a frame
with port-based priority using
a Q-tag.
Priority
ONS node uses a Q-tag to
map a frame with priority and
forwards it on.
The ONS node uses a "leaky bucket" algorithm to establish a weighted priority. A weighted priority, as
opposed to a strict priority, gives high-priority packets greater access to bandwidth, but does not totally
preempt low-priority packets. During periods of network congestion, about 70 percent of bandwidth
goes to the high-priority queue and the remaining 30 percent goes to the low-priority queue. A network
that is too congested will drop packets.
IEEE 802.1Q was formerly known as IEEE 802.1P.
Note
E-Series cards in port-mapped mode and G-Series cards do not support priority queing (IEEE 802.1Q).
Note
E-Series Spanning Tree (IEEE 802.1D)
The E-Series operates IEEE 802.1D Spanning Tree Protocol (STP). The E-Series card supports common
STPs on a per-circuit basis up to a total of eight STP instances. It does not support per-VLAN STP. In
single-card mode, STP can be disabled or enabled on a per-circuit basis during circuit creation. Disabling
STP will preserve the number of available STP instances.
Cisco ONS 15454 and Cisco ONS 15454 SDH Ethernet Card Software Feature and Configuration Guide, R8.0
23-20
Priority Queuing Process
Data Flow
Priority
Same
priority
Chapter 23 E-Series and G-Series Ethernet Operation
Priority tag
removed
The receiving ONS node
removes the Q-tag and
forwards the frame.
Priority
The receiving ONS node
receives the frame with a
Q-tag and forwards it.