Introduction
Ring automatic protection switching (G.8032) is introduced in both SAS-E and SAS-M from R3.0 R1 onwards. SAS-X supports it starting 3.0R2. G.8032 is used to prevent loops in a ring network by blocking one of the links, this is an alternative to STP/RSTP and the recovery switching is much faster then the traditional STP/RSTP, (i.e within a few hundred milliseconds). G.8032 can only be enabled on access ports (dot1q and qinq) or access uplink ports using qinq encapsulations.
Description:-
Given below are some of the general terms which are used in G.8032:-
Ring Protection Link (RPL) – Link designated by mechanism that is blocked during Idle state to prevent loop on Bridged ring.
RPL Owner – Node connected to RPL that blocks traffic on RPL during Idle state and unblocks during Protected state.
Ring APS (R-APS) Messages – Protocol messages defined in Y.1731 and G.8032. These are exchanged between the RPL owner and other nodes similar to BPDU in STP.
Link Monitoring – Links of ring are monitored using standard ETH CC OAM messages (CFM).
Signal Fail (SF) – Signal Fail is declared when CCM messages are not received from the peer MEP hence a signal fail condition is detected .
No Request (NR) – No Request is declared when there are no outstanding conditions (e.g., SF, etc.) on the node ie like R-APS (NR).
G.8032 states:-
Ring Nodes may be in one of the two states
Idle
Protection
Idle:- Normal operation no link/node faults detected on the link. Physical topology has all nodes connected in a ring and the Logical topology has all nodes connected without a loop. Each link is monitored by its two adjacent nodes using ETH CC OAM messages.
Given below is an example of the idle state as you can see in the diagram, SAS-E has blocked one of the nodes which belongs to the RPL owner.
Protection state:-
Link/node failure is detected by the nodes adjacent to the failure. The nodes adjacent to the failure block the failed link and report this failure to the ring using R-APS Signal Failure (SF) message. When R-APS (SF) message is received by the RPL owner, it unblocks the blocked port and performs FDB flushing.
Given below is the topology where we see that the RPL owner has unblocked the previously blocked link.
Link Recovery:-
When the failed link recovers, the traffic is kept blocked on the nodes adjacent to the recovered link. The nodes adjacent to the recovered link transmit R-APS No Request (NR) message indicating they have no local request present. When the RPL Owner receives R-APS (NR) message it Starts WTR timer also known as Time to Revert. Once Revert timer expires, RPL Owner blocks RPL and transmits R-APS (NR, RB) message. RB is a 1 bit flag set by the RPL owner when one of the ports in RPL is blocked this is always sent with R-APS (NR) message. Nodes receiving the message – perform a FDB Flush and unblock their previously blocked ports. Ring is now returned to Idle state. These are explained in the diagram below.
G.8032 Modes:-
G.8032 operates in two modes Revertive and Non Revertive.
In revertive mode the RPL link will be the link that is blocked and all the other links will be operable after the revert time. This is the default mode.
In non revertive mode the last failed link will be blocked and the RPL need not be configured in any 7210’s.
Revertive mode offers more predictability as the operator can control which link needs to be blocked.
Configuring G.8032
Given below is the topology which will be used for the configurations. Here we have 3 SASE which are configured in a ring.
Y.1731 needs to be configured on all the SAS-E devices given below is the configuration. All the devices are in the same domain, with two different associations configured for each SASEs.
Configuration on SASE1 :-
*A:G.SAS-E1>config>eth-cfm# info
----------------------------------------------
domain 1 format none level 1
association 1 format icc-based name "samratdutta12"
bridge-identifier 2
exit
ccm-interval 1
remote-mepid 2
exit
association 3 format icc-based name "samratdutta14"
bridge-identifier 2
exit
ccm-interval 1
remote-mepid 3
exit
exit
----------------------------------------------
*A:G.SAS-E1>config>eth-cfm#
Configuration for SASE2 is as follows:-
*A:SAS-E2>config>eth-cfm# info
----------------------------------------------
domain 1 format none level 1
association 1 format icc-based name "samratdutta12"
bridge-identifier 2
exit
ccm-interval 1
remote-mepid 1
exit
association 2 format icc-based name "samratdutta16"
bridge-identifier 2
exit
ccm-interval 1
remote-mepid 6
exit
exit
----------------------------------------------
Configuration for SASE3 is as follows:-
A:G.SASE-3>config>eth-cfm# info
----------------------------------------------
domain 1 format none level 1
association 2 format icc-based name "samratdutta16"
bridge-identifier 2
exit
ccm-interval 1
remote-mepid 10
exit
association 3 format icc-based name "samratdutta14"
bridge-identifier 2
exit
ccm-interval 1
remote-mepid 12
exit
exit
----------------------------------------------
Please Note:- By default the CCM ’s are sent every 10 seconds, the least CCM interval that can be configured is 100 ms.
Next we need to configure an Eth-ring for all the SAS-E devices.
Configuration on SASE1:-
*A:SASE-1>config>eth-ring# info
----------------------------------------------
revert-time 100
rpl-node owner
path a 1/1/11 raps-tag 105.100
rpl-end
eth-cfm
mep 1 domain 1 association 1
ccm-enable
control-mep
no shutdown
exit
exit
no shutdown
exit
path b 1/1/12 raps-tag 105.100
eth-cfm
mep 12 domain 1 association 3
ccm-enable
control-mep
no shutdown
exit
exit
no shutdown
exit
no shutdown
----------------------------------------------
Please Note:- As SASE1 is configured with rpl-node-owner this is an RPL owner.
Path A is configured as rpl-end hence this particular link is an RPL protection link and will be blocked in the idle state.
Configuration on SASE2:-
*A:G.SASE-2>config>eth-ring# info
----------------------------------------------
path a 1/1/11 raps-tag 105.100
eth-cfm
mep 2 domain 1 association 1
ccm-enable
control-mep
no shutdown
exit
exit
no shutdown
exit
path b 1/1/12 raps-tag 105.100
eth-cfm
mep 10 domain 1 association 2
ccm-enable
control-mep
no shutdown
exit
exit
no shutdown
exit
no shutdown
----------------------------------------------
Configuration on SASE3:-
A:G.SASE-3>config>eth-ring# info
----------------------------------------------
path a 1/1/11 raps-tag 105.100
eth-cfm
mep 3 domain 1 association 3
ccm-enable
control-mep
no shutdown
exit
exit
no shutdown
exit
path b 1/1/12 raps-tag 105.100
eth-cfm
mep 6 domain 1 association 2
ccm-enable
control-mep
no shutdown
exit
exit
no shutdown
exit
no shutdown
----------------------------------------------
Please Note:- rpl-end or rpl-owner is not configured on SASE2 and SASE3 since it is not an RPL node.
Then a service needs to be created to bind the Eth-ring.
A:SASE-1>config>service>vpls# info
----------------------------------------------
stp
shutdown
exit
sap 1/1/11 :105.100 eth-ring 2 create
stp
shutdown
exit
statistics
egress
exit
ingress
counter-mode packet
exit
exit
exit
sap 1/1/12 :105.100 eth-ring 2 create
stp
shutdown
exit
statistics
egress
exit
ingress
counter-mode packet
exit
exit
exit
no shutdown
----------------------------------------------
Please Note:- This service is not intended to send the customer traffic.
Finally we need to create service for the data traffic.
A:SASE-1>config>service>vpls# info
----------------------------------------------
stp
no shutdown
exit
sap 1/1/11 :110.* eth-ring 2 create
statistics
egress
exit
ingress
counter-mode packet
exit
exit
exit
sap 1/1/12 :110.* eth-ring 2 create
statistics
egress
exit
ingress
counter-mode packet
exit
exit
exit
no shutdown
----------------------------------------------
Same services needs to be created for the data traffic on the other nodes also.
Verification:-
*A:SASE-1# show eth-ring 2
===============================================================================
Ethernet Ring 2 Information
===============================================================================
Description : (Not Specified)
Node ID : 00:25:ba:00:53:e1
Guard Time : 5 deciseconds RPL Node : rplOwner
Max Revert Time : 100 seconds Time to Revert : N/A
CCM Hold Down Time : 0 centiseconds CCM Hold Up Time : 20 deciseconds
APS Tx PDU : Request State: 0x0
Sub-Code : 0x0
Status : 0xC0 ( RB DNF )
Node ID : 00:25:ba:00:53:e1
Defect Status :
-------------------------------------------------------------------------------
Ethernet Ring Path Summary
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
a 1/1/11 105.100 Up/Up rplEnd blocked
b 1/1/12 105.100 Up/Up normal unblocked
As we see in the above output SASE1 is the RPL node owner and the RPL link will be blocked.
Output on SASE2:-
A:G.SASE-2# show eth-ring 2
===============================================================================
Ethernet Ring 2 Information
===============================================================================
Description : (Not Specified)
Node ID : 00:25:ba:00:45:71
Guard Time : 5 deciseconds RPL Node : rplNone
Max Revert Time : 0 seconds Time to Revert : N/A
CCM Hold Down Time : 0 centiseconds CCM Hold Up Time : 20 deciseconds
APS Tx PDU : N/A
Defect Status :
-------------------------------------------------------------------------------
Ethernet Ring Path Summary
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
a 1/1/11 105.100 Up/Up normal unblocked
b 1/1/12 105.100 Up/Up normal unblocked
===============================================================================
Output on SASE3:-
A:SASE-3# show eth-ring 2
===============================================================================
Ethernet Ring 2 Information
===============================================================================
Description : (Not Specified)
Node ID : 00:25:ba:00:3a:9d
Guard Time : 5 deciseconds RPL Node : rplNone
Max Revert Time : 0 seconds Time to Revert : N/A
CCM Hold Down Time : 0 centiseconds CCM Hold Up Time : 20 deciseconds
APS Tx PDU : N/A
Defect Status :
-------------------------------------------------------------------------------
Ethernet Ring Path Summary
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
a 1/1/11 105.100 Up/Up normal unblocked
b 1/1/12 105.100 Up/Up normal unblocked
===============================================================================
Please Note:- As we can see in the above outputs the ports on SASE2 and E3 are unblocked as it is not the rpl-node.
When the link between SASE2 and SASE3 breaks the following messages are displayed on the console:-
"Eth-Ring 2 path 0 changed fwd state to unblocked"
"Topology change for service 10 (customer 1) due to SAP 1/1/12 :110.* major state
change"
Verification:-
*A:SASE-1# show eth-ring 2
========================================================================
Ethernet Ring 2 Information
========================================================================
Description : (Not Specified)
Node ID : 00:25:ba:00:53:e1
Guard Time : 5 deciseconds RPL Node : rplOwner
Max Revert Time : 100 seconds Time to Revert : N/A
CCM Hold Down Time : 0 centiseconds CCM Hold Up Time : 20 deciseconds
APS Tx PDU : N/A
Defect Status :
-------------------------------------------------------------------------------
Ethernet Ring Path Summary
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
a 1/1/11 105.100 Up/Up rplEnd unblocked
b 1/1/12 105.100 Up/Up normal unblocked
=============================================================
As we can see above the previously blocked port have been unblocked.
Output on SASE2:-
*A:SAS-E2# show eth-ring 2
===============================================================================
Ethernet Ring 2 Information
=============================================================
Description : (Not Specified)
Node ID : 00:25:ba:00:45:71
Guard Time : 5 deciseconds RPL Node : rplNone
Max Revert Time : 0 seconds Time to Revert : N/A
CCM Hold Down Time : 0 centiseconds CCM Hold Up Time : 20 deciseconds
APS Tx PDU : Request State: 0xB
Sub-Code : 0x0
Status : 0x20 ( BPR )
Node ID : 00:25:ba:00:45:71
Defect Status :
-------------------------------------------------------------------------------
Ethernet Ring Path Summary
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
a 1/1/11 105.100 Up/Up normal unblocked
b 1/1/12 105.100 Up/Down normal blocked
==============================================================
As the link between SASE2 and SASE3 is broken hence the port between SASE2 and E3 is blocked.
Output on SASE3:-
===================================================================
Ethernet Ring 2 Information
===================================================================
Description : (Not Specified)
Node ID : 00:25:ba:00:3a:9d
Guard Time : 5 deciseconds RPL Node : rplNone
Max Revert Time : 0 seconds Time to Revert : N/A
CCM Hold Down Time : 0 centiseconds CCM Hold Up Time : 20 deciseconds
APS Tx PDU : Request State: 0xB
Sub-Code : 0x0
Status : 0x20 ( BPR )
Node ID : 00:25:ba:00:3a:9d
Defect Status :
-------------------------------------------------------------------------------
Ethernet Ring Path Summary
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
a 1/1/11 105.100 Up/Up normal unblocked
b 1/1/12 105.100 Up/Down normal blocked
===================================================================
When the links are restored:-
After the links between SASE2 and SASE3 is restored the the RPL owner (SASE1) will only block the RPL link when the revert timer has expired.
As we can see below the rpl link is still blocked as the revert timer has not expired.
Verification:-
A:SASE-1# show eth-ring 2
=====================================================================
Ethernet Ring 2 Information
=====================================================================
Description : (Not Specified)
Node ID : 00:25:ba:00:53:e1
Guard Time : 5 deciseconds RPL Node : rplOwner
Max Revert Time : 100 seconds Time to Revert : 88 seconds
CCM Hold Down Time : 0 centiseconds CCM Hold Up Time : 20 deciseconds
APS Tx PDU : N/A
Defect Status :
-------------------------------------------------------------------------------
Ethernet Ring Path Summary
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
a 1/1/11 105.100 Up/Up rplEnd unblocked
b 1/1/12 105.100 Up/Up normal unblocked
=====================================================================
After the revert timer expires the following messages is displayed on the console:-
"Eth-Ring 2 path 0 changed fwd state to blocked"
And the rpl link is blocked.
A:SASE-1# show eth-ring 2
====================================================================
Ethernet Ring 2 Information
====================================================================
Description : (Not Specified)
Node ID : 00:25:ba:00:53:e1
Guard Time : 5 deciseconds RPL Node : rplOwner
Max Revert Time : 100 seconds Time to Revert : N/A
CCM Hold Down Time : 0 centiseconds CCM Hold Up Time : 20 deciseconds
APS Tx PDU : Request State: 0x0
Sub-Code : 0x0
Status : 0x80 ( RB )
Node ID : 00:25:ba:00:53:e1
Defect Status :
-------------------------------------------------------------------------------
Ethernet Ring Path Summary
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
a 1/1/11 105.100 Up/Up rplEnd blocked
b 1/1/12 105.100 Up/Up normal unblocked
=====================================================================
G.8032 in non revertive mode:-
When G.8032 operates in non-revertive mode no revert timer or rpl-end needs to be configured and the last failed link is always blocked.
Configuration:-
A:G.8032-1>config>eth-ring# info
----------------------------------------------
no revert-time
path a 1/1/11 raps-tag 105.100
eth-cfm
mep 1 domain 1 association 1
ccm-enable
control-mep
no shutdown
exit
exit
no shutdown
exit
path b 1/1/12 raps-tag 105.100
eth-cfm
mep 12 domain 1 association 3
ccm-enable
control-mep
no shutdown
exit
exit
no shutdown
exit
no shutdown
Hi Sammy,
ReplyDeleteThanks for sharing the details.
Do you have some more details about the definitions of the eth-cfm building blocks of SAS-X equipments
cheers
Pankaj