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NE40E-M2 V800R010C10SPC500 Feature Description - LAN Access and MAN Access 01

This is NE40E-M2 V800R010C10SPC500 Feature Description - LAN Access and MAN Access
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R-APS PDU Format

R-APS PDU Format

Ethernet Ring Protection Switching (ERPS) protocol packets are called R-APS PDUs. Ring Auto Protection Switching (R-APS) Protocol Data Units (PDUs) are transmitted on ERPS rings to convey ERPS ring information. Figure 12-5 shows the basic R-APS PDU format.

Figure 12-5 Basic R-APS PDU format

Table 12-4 describes the fields in an R-APS PDU.

Table 12-4 R-APS PDU field description

Field Name

Length

Description

MEL

3 bits

Identifies the maintenance entity group (MEG) level of the R-APS PDU.

Version

5 bits

  • 0x00: used in ERPSv1.
  • 0x01: used in ERPSv2.

OpCode

8 bits

Indicates an R-APS PDU. The value of this field is 0x28.

Flags

8 bits

Is reserved. The value of this field is fixed at 0x00.

TLV Offset

8 bits

Indicates that the TLV starts after an offset of 32 bytes. The value of this field is fixed at 0x20.

R-APS Specific Information

32 x 8 bits

Carries R-APS ring information and is the core in an R-APS PDU. This field has different meanings for some of its sub-fields in ERPSv1 and ERPSv2. Figure 12-6 shows the R-APS Specific Information field format in ERPSv1. Figure 12-7 shows the R-APS Specific Information field format in ERPSv2.

TLV

Not limited

Describes information to be loaded. The end TLV value is 0x00.

Figure 12-6 R-APS Specific Information field format in ERPSv1

Figure 12-7 R-APS Specific Information field format in ERPSv2

Table 12-5 describes sub-fields in the R-APS Specific Information field.
Table 12-5 Sub-fields in the R-APS Specific Information field

Sub-Field Name

Length

Description

Request/State

4 bits

Indicates that this R-APS PDU is a request or state PDU. The value can be:

  • 1101: forced switch (FS)

  • 1110: Event

  • 1011: signal failed (SF)

  • 0111: manual switch (MS)

  • 0000: no request (NR)

  • Others: reserved

Reserved 1

4 bits

Reserved 1 is used in ERPSv1 for message reply or protection identifier.

Sub-code is used in ERPSv2 with its value determined by the Request/State field value:
  • If the Request/State field value is 1110, the Sub-code value is 0000, meaning Flush Request.
  • If the Request/State field value is any value other than 1110, the Sub-code value is 0000 and ignored upon reception.

Sub-code

Status

8 bits

Includes the following status information:
  • RPL Blocked (RB) (1 bit): If the value is 1, the RPL owner port is blocked; if the value is 0, the RPL owner port is unblocked. The nodes without the RPL owner port set this sub-field to 0 when sending an R-APS PDU.

  • Do Not Flush (DNF) (1 bit): If the value is 1, an FDB flush should not be triggered by the reception of the R-APS PDU; if the value is 0, an FDB flush may be triggered by the reception of the R-APS PDU.

  • Blocked port reference (BPR) (1 bit): If the value is 0, ring link 0 is blocked; if the value is 1, ring link 1 is blocked.

    BPR is valid only in ERPSv2.

  • Status Reserved (5 bits): This sub-field is reserved for future specification and should be ignored upon reception. This sub-field should be encoded as all 0s in transmission.

Node ID

6 x 8 bits

Identifies the MAC address of a node on the ERPS ring. It is informational and does not affect protection switching on the ERPS ring.

Reserved 2

24 x 8 bits

Reserved for future extension and should be ignored upon reception. Currently, this sub-field should be encoded as all 0s in transmission.

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Updated: 2019-01-02

Document ID: EDOC1100058405

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