G.8032 for Ethernet Networks
Ethernet Ring Protection
Yaacov Weingarten
Nokia Siemens Networks
Slide 1
CET Technologies/ Yaacov Weingaten / 11-05-08
Nokia Siemens Networks / Industry Environment/ CET
Agenda
• Why Rings?
• Status of G.8032
• Multiple instances – bandwidth efficiency
• Inter-connected rings
• Operator commands
Slide 2
CET Technologies / Yaacov Weingarten / 11-05-08
Nokia Siemens Networks / Industry Environment / WiSDoM
Why Rings?
• Considered the simplest redundant topologies and are
often encountered in Metropolitan Ethernet Networks
(Metro) to minimize optical fiber usage.
• Effective means of aggregating DSLAMs or small Ethernet
switches in multi-tenant or multi-dwelling environments in
Metro access networks
Slide 3
CET Technologies / Yaacov Weingarten / 11-05-08
Nokia Siemens Networks / Industry Environment / WiSDoM
Status of G.8032
• Recommendation was consented within working group in Feb 2008
• Sent for Last Call comments during month of April
– Four companies submitted comments
– Technical comments were addressed during interim meeting, 30 Apr – all resolved to
satisfaction of commenting companies
– Additional resolution (of editorials) within two weeks
• Begun work on next revision of the Recommendation. New revision will address:
– Multiple Instances
– Inter-connected ring topologies and protection
– Operator commands – e.g. Manual switch, Forced switch
Slide 4
CET Technologies / Yaacov Weingarten / 11-05-08
Nokia Siemens Networks / Industry Environment / WiSDoM
Multiple Instances – bandwidth efficiency
• Ability to configure different logical rings that are protected, each with its
own RPL (and RPL Owner).
• Allows greater utilization of all the links in the ring, possibly in different
logical rings
• Each ring is addressed separately in R-APS messages
– Using VID or different MAC address (in SA)
Slide 5
CET Technologies / Yaacov Weingarten / 11-05-08
Nokia Siemens Networks / Industry Environment / WiSDoM
Interconnected Rings – General Objectives
• Only “reasonable” carrier topologies (that would be configured in
actual operator/service provider domains) should be addressed.
– The rules defining the Interconnected ring topologies supported are expressed
in following slides.
• Ring interconnection should not require changes to the single ring
protection mechanism.
– Although there may be a need to add features to the APS protocol, the basic
messages and interactions should not be affected.
• Nodes that are not at the ends of shared links should not need
special provisioning to support shared links in the ring
• When a shared link fails, it is necessary to prevent the formation of
a super loop, as may be the case if both rings protect at the same
time.
Slide 6
CET Technologies / Yaacov Weingarten / 11-05-08
Nokia Siemens Networks / Industry Environment / WiSDoM
Interconnected Rings – General Guidelines
• Shared link may act as the RPL for only one of the rings that
share the link
• A signal failure on a non-shared link (when the ring is in idle
state) should only trigger protection switching within the ring
where the link failed, the other interconnected rings should be
agnostic to this event
Slide 7
CET Technologies / Yaacov Weingarten / 11-05-08
Nokia Siemens Networks / Industry Environment / WiSDoM
Interconnected Rings – Topology rules
General consensus at ITU discussions to set principles of
interconnected ring topologies that will be supported
• Interconnected rings may share more than
one shared link
ERP1
ERP2
• A node that is common to different rings
may be connected by more than one shared
link
• A shared link may be shared by more than
two rings
ERP1
ERP2
ERP3
ERP2
ERP1
ERP3
Slide 8
CET Technologies / Yaacov Weingarten / 11-05-08
Nokia Siemens Networks / Industry Environment / WiSDoM
ERP3
Interconnected Rings – Topology Limitations
• Interconnected rings shall not
form a ring of rings
• Two rings shall not be connected
by two shared nodes if the link
between these nodes is not
shared (when two links exist
between the two shared nodes)
• Two rings shall not be connected
by any two shared links if these
links are not connected to the
same shared node
Slide 9
CET Technologies / Yaacov Weingarten / 11-05-08
ERP1
ERP2
ERP3
ERP4
Shared node
Ring A
Ring B
Shared node
Non shared link
Non shared link
Nokia Siemens Networks / Industry Environment / WiSDoM
Interconnected Rings – Priority-based protection
Nokia Siemens Networks proposes to assign a priority to each RPL,
through configuration
When Shared link fails – only RPL with highest priority protects ring,
thereby preventing formation of super loop
89
ERP1
ERP1
ERP2
ERP2
78
c. If both rings perform protection switching, a “super
loop” is created
a. Adjacent rings in idle state with RPL blocked
89
ERP1
ERP1
ERP2
ERP2
78
b. Signal fault discovered on shared link
Slide 10
CET Technologies / Yaacov Weingarten / 11-05-08
d. if higher priority ring performs protection switching
no loop is created
Nokia Siemens Networks / Industry Environment / WiSDoM
Operator commands – Manual/Forced Switch
• Operator has need to intervene into current flow control of the ring
• Updating node software
• Switching hardware – switch out/in of new nodes or links
• Periodic maintenance
• Support for commands to the ring – Manual Switch or Forced Switch
• Need to establish relative priority between commands and Signal Fault
situations
• Switch mechanism and recovery
• Treat special cases – sequential requests, simultaneous requests
• General consensus reached at last interim meeting
• Forced Switch > higher than Signal Failure > higher than Manual Switch
• Simultaneous requests – Manual Switch cancel out, Forced Switch co-exist
Slide 11
CET Technologies / Yaacov Weingarten / 11-05-08
Nokia Siemens Networks / Industry Environment / WiSDoM
Manual Switch behavior
RPL
A
B
C
D
E
G
F
1
Manual
Switch
2
Idle
3
MS
MS
MS
4
Manual
Switch
state
5
6
7
8
Flush
MS
MS
Flush
Flush
NR
NR
NR
NR
NR RB
Flush
NR RB
Flush
NR RB
NR RB
NR
NR
NR RB
NR RB
Flush
9
Slide 12
MS
Clea
r
NR RB
Idle
MS
Flush
Flush
Flush
Flush
MS
NR RB
CET Technologies / Yaacov Weingarten / 11-05-08
NR RB
NR
NR RB
NR RB
NR RB
Flush
Flush
Flush
Flush
NR RB
NR
NR RB
Nokia Siemens Networks / Industry Environment / WiSDoM
NR RB
NR RB
Slide 13
CET Technologies/ Yaacov Weingaten / 11-05-08
Nokia Siemens Networks / Industry Environment/ CET