Alcatel-Lucent 9500 MXC User Manual page 183

3DB 23063 ADAA - Rev 004 July 2007
• DAC GE includes an RSTP switch function in the form of RWPR
provides fast-switched, enhanced RSTP operation.
• Unlike normal RSTP action, which involves a progressive exchange of
messages between all nodes beginning with those immediately adjacent to
the failure point, the RWPR uses a unique fast-link-detection (FLD)
mechanism to rapidly and reliably detect a failure on one of the transport
channels, and to then communicate immediately with participating RWPR
ring nodes when a ring re-configuration is required. Depending on the
network topology re-convergence can be within 50 ms.
Ring-wrapping is not used, rather Ethernet traffic is carried on point-to-point
circuits on the ring. See Point-to-Point Traffic Overlay on a Ring on page 3-83.
RSTP service restoration or 're-convergence' times are typically 1 to 5 seconds.
By comparison, the earlier Spanning Tree Protocol (STP) exhibited a
convergence time of about 50 seconds.
RWPR supports re-convergence times of less than a second, typically 50 msecs
for a five-node ring and less than 100 msecs for a ten node ring.
Ethernet Ring Solutions
9500 MXC Nodes support Fast and Gigabit Ethernet rings:
• 9500 MXC Node with the DAC ES supports Ethernet rings to 100 Mbps.
• A single DAC ES is configured to provide two transport channels, one to the
east RAC, the other to the west, from an external RSTP switch.
• E1/DS1 traffic may also be configured in the ring, which may be
point-to-point (not protected) or ring-wrap protected.
• A single 9500 MXC Node with a DAC GE supports Gig-Ethernet rings to 150
Mbps. One DAC GE is configured to provide two transport channels, one to the
east RAC, the other to the west. No external RSTP switch is required.
• Two INUs may be co-located at each site to support a 300 Mbps ring. The 300
Mbps throughput may be configured on single 300 Mbps links, or as two
co-path, link-aggregated 150 Mbps links.
• Four INUs may be co-located to support a 600 Mbps ring using two co-path,
link-aggregated 300 Mbps links, or four co-path, link-aggregated 150 Mbps
links.
Figure 3-55 shows a 9500 MXC ring configured for RSTP protection of Ethernet
traffic using an external RSTP switch, and ring-wrap protection of NxE1 traffic.
• Point-to-point circuits are configured for Ethernet traffic, and via the DAC ES
are ported to an external RSTP switch, which manages the ring protection. Note
that the 2 Mbps circuits designated to carry the Ethernet traffic (1 - 16) are
reused on each radio link to provide superior ring-traffic efficiency, compared
to ring-wrap protection of Ethernet traffic.
9500 MXC User Manual
TM
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Vol. II-3-89