15-03-2008 802-17 Yan Wang

Proposed amendments of control frames for 802.17c

Yan WangHuawei technologies

15-03-2008 802-17 Yan Wang

New Control Frames

• PIRC frame – Exchange and notify the status messages between the

mate stations on the ring.

• Peer message– The message between the peer stations. What should it

be?

• Reversion notify frame– Notify the defect reversion to the inter-ring station

when multiple links failure protection is used. It is helpful to loop prevention.

15-03-2008 802-17 Yan Wang

Clause 9 Frame Formats

• 9.3 Control frame format– 9.3.2 Control frame fields

– Insert the following value 0C16 information field in Table 9.4, after the 0B16 entry.

0C16 CT_OAM_PIRC_STATUS OAM PIRC status notify frame

15-03-2008 802-17 Yan Wang

Clause 11: Topology discovery and protection

• 11.4 Defined ATT encodings• 11.4.3 Station settings ATT

– Replace Figure 11.18 with the following figure.

– Replace section 11.4.3.1 with the following text.• 11.4.3.1 res: A 3-bit reserved field.

– Insert the following station setting immediately following 11.4.3.1. Renumber as necessary.

• 11.4.3.2 pirc: A (protected inter-ring connection) bit that is set to 1 if the station is a inter-ring connection station, based on the value of myTopoInfo.pircUser. Otherwise, this bit has a default 0 value.

– Change the last paragraph of 11.4.3 as follows.• When received, this information is copied to the pircUser, sasUser, badFcsUser,

conservativeMode, and multichokeUser fields in the topology database.

mucobfsaspircres1

MSB LSB

15-03-2008 802-17 Yan Wang

Clause 12: Operations, administration, and maintenance (OAM)

• 12.1 Overview– Add the following item to the end of the list.

• f) Provide a mechanism to exchange and notify status messages between the mate stations on the ring.

• 12.1.2 OAM functions supported by RPR– Add the following additional OAM frame type supported to the end of the

list.• e) PIRC management—For status exchange and notify between the mate

stations.

• 12.1.7 PIRC management operations– A PIRC frame allows one interconnected station to notify its status and

characteristic to its mate station in the same protection group. The PIRC frame is broadcast over the rings with a service class of subclassA0.

– PIRC frames are received by all stations, processed by the inter-ring stations.

15-03-2008 802-17 Yan Wang

PIRC Frame

12.3 OAM frame formats• Insert the following section, 12.3.5, after 12.3.4.

– 12.3.5 PIRC frame• The PIRC frames are identified by the controlType field

value of CT_OAM_PIRC_STATUS and a controlVersion value of 0. The PIRC frame is only sent by the inter-ring station. The PIRC frame contents include information about the sending station’s status and characteristic. Figure 12.13 illustrates the PIRC frame payload with the controlDataUnit portion of the frame indicated. The header fields (specified in 9.3, but not illustrated here) are additionally constrained as specified in Table 12.5.

15-03-2008 802-17 Yan Wang

PIRC Frame Payload Format

Device ID

Status

Priority

Protection Group ID

controlVersion

controlType

4

1

1

1

1

1

controlDataUnit

Figure 12.13

15-03-2008 802-17 Yan Wang

PIRC Frame Header Field-value Restrictions

Field Sub-Field Value Description

ttl - MAX_Stations Allow PIRC frames to propagate through all stations.

baseControl sc CLASS_A0 Sent as subclassA0.

fe FAULT Not fairness eligible.

da - FF-FF-FF-FF-FF-FF Allow PIRC frames to be received by any station.

Table 12.5

15-03-2008 802-17 Yan Wang

• Protection Group ID– Identify a protection group.

• Status– The status field consists of multiple sub-fields, as illustrated in

the following figure.

– res: Reserved.

– lb: A load balancing bit marks if the station is working in load balancing mode.

– fs: Two forwarding status bits identify the forwarding status.

PIRC Frame Payload

1

fslbres

MSB LSB

15-03-2008 802-17 Yan Wang

Sub-fields of Status

lb fs Description

0 0 0 The inter-ring forwarding function is down. No inter-ring traffic is forwarded by it.

0 0 1 Load balancing is not used. The inter-ring station is an active station. All inter-ring traffic is forwarded by it.

0 1 0 Load balancing is not used. The station is a standby station. No inter-ring traffic is forwarded by it.

0 1 1 Load balancing is not used. Its mate station is down, so all inter-ring traffic is forwarded by it.

1 0 0 The inter-ring forwarding function is down. No inter-ring traffic is forwarded by it.

1 0 1 Load balancing is used. The traffic set 1 is forwarded by it.

1 1 0 Load balancing is used. The traffic set 2 is forwarded by it.

1 1 1 Load balancing is used. Its mate station is down, so all inter-ring traffic is forwarded by it.

• Traffic sets are the sets of different VLANs, methods such as hashing, manual configuration etc. can be use to decide which set a VLAN belongs to.

15-03-2008 802-17 Yan Wang

PIRC Frame Payload

• Priority– The Priority of the inter-ring station. – It is used to decide the role of inter-ring station (active/standby,

traffic set1/traffic set 2). Such as the station with higher priority should be the active one.

– When forwarding status conflict happens, it can also be used to decide which station should change its forwarding status. This can be used in Manual Switch.

• Device ID– The inter-ring station’s device ID. – It can be used for management, and when it happens that two

mate stations’ priorities are same, the device ID can also be used to solve the forwarding status conflict.

15-03-2008 802-17 Yan Wang

State Machine

Normal

Fai l ureProtecti on Peer/ Sel fdown

Peer/ Sel fup

Mate down

Peer/ Sel fdown

Mate up

Start

15-03-2008 802-17 Yan Wang

Forwarding States

• Normal state: – In the active/standby mode, the station forwards all or

none of the inter-ring traffic. In the load balancing mode, the station forwards traffic set 1 or set 2.

• Protection state:– Forwarding all inter-ring traffic because of the mate

failures or multiple links failure protection.

• Failure state: – Inter-ring traffic can’t be forwarded because of self

down or peer down.

15-03-2008 802-17 Yan Wang

PIRC Frames and State Transform

• PIRC frame is sent periodically by the inter-ring station when it is in normal state.

• PIRC frame is sent immediately by the inter-ring station when its forwarding state changes.

• Mate up/down messages are carried by PIRC frame.• When received mate status message is incompatible with

local inter-ring, forwarding status may be changed according to the priorities.

• Hold-off timer is needed to prevent loop when the inter-ring station status changes from non-forwarding to forwarding.

15-03-2008 802-17 Yan Wang

Peer Message

• It shall not be the RPR frame. Should it be standardized in a RPR standard?– When the two peer stations are in one equipment, the

peer messages may be some interior instructions.– When the two peer stations are two independent

equipments and connected by a link, the message format is related with the connecting port.

– Few possibilities that peer stations are from different vendors.

– We can just request the station has the ability to find the failure between peer stations.

15-03-2008 802-17 Yan Wang

Multiple Links Failure Protection

• C2 is selected to forward the inter-ring traffic.

• Two links failure makes R1 can’t communicate with C2, inter-ring traffic from R1 fails.

• Protection is achieved by both inter-ring nodes C1 and C2 forwarding all inter-ring traffic.

C2 R4

R3R1

R2

C1

C2 R4

R3R1

R2

C1

C2 R4

R3R1

R2

C1

15-03-2008 802-17 Yan Wang

Transient Loop Prevention

• When nodes R1 and R2 find the link recovers, they shouldn’t switch to normal status immediately. – They keep in protected status until their timers expire.– Before the timers expire, the correlative interconnected node

C1 shall know the reversion and stop forwarding. R1 and R2 can send reversion notify frame to the interconnected node C1 and C2.

– Timers should be configured appropriately, timers expire after node C1 stops forwarding and topology converges.

C2 R4

R3R1

R2

C1

C2 R4

R3R1

R2

C1

C2 R4

R3R1

R2

C1

15-03-2008 802-17 Yan Wang

Clause 9 Frame Formats

• 9.3 Control frame format– 9.3.2 Control frame fields

– Insert the following value 0D16 information field in Table 9.4, after the 0C16 entry.

0D16 CT_OAM_REVERSION OAM reversion notify frame for PIRC

15-03-2008 802-17 Yan Wang

Clause 12: Operations, administration, and maintenance (OAM)

• 12.1 Overview– Add the following item to the end of the list.

• g) Provide a mechanism to notify the defect reversion to the inter-ring station when multiple links failure protection is used.

• 12.1.2 OAM functions supported by RPR– Add the following additional OAM frame type supported to the end of the

list.• f) Reversion notify—Notify the defect reversion to the inter-ring station when

multiple links failure protection is used.

• 12.1.8 Reversion notify operations– A Reversion notify frame allows one station near the reversion link can

notify the interconnected node to change its forwarding status to avoid transient loop when multiple links failure protection is used. The Reversion notify frame is broadcast over the ring with a service class of subclassA0.

– Reversion notify frames are received by all stations, processed by the inter-ring stations.

15-03-2008 802-17 Yan Wang

Reversion Notify Frame

12.3 OAM frame formats• Insert the following section, 12.3.6, after 12.3.5.

– 12.3.6 Reversion notify frame• The recover notify frames are identified by the controlType field value

of CT_OAM_REVERSION and a controlVersion value of 0. The recover notify frame is sent by the stations which are near the recovered link. Receiving the recover notify frame, the inter-ring station possibly changes its forwarding status according to its current status and configuration.

Reserved

controlVersion

controlType1

1

1

controlDataUnit

15-03-2008 802-17 Yan Wang

Reversion Notify Frame Header Field-value Restrictions

Field Sub-Field Value Description

ttl - MAX_Stations Allow Reversion notify frames to propagate through all stations.

baseControl sc CLASS_A0 Sent as subclassA0.

fe FAULT Not fairness eligible.

da - FF-FF-FF-FF-FF-FF Allow Reversion notify frames to be received by any station.