Friday, April 1, 2016

Forwarding Framework on the Device

For OLT device

NOTE:
The difference among the following forwarding tables is the first-level and second-level indexes. For example, the first-level and second-level index in the GPON multicast forwarding table (VLAN+GIP) is VLAN+GIP.

GPON Multicast Forwarding Table (VLAN+GIP) [OLT]

Figure 1 GPON multicast forwarding table (VLAN+GIP) 
 
The OLT supports a distributed 2+1-level duplication architecture:
  • The first-level duplication is implemented on the control board. By using the "VLAN+GIP" index, the control board duplicates multicast data to the service board interested in the multicast program in an as-per-requirement manner, effectively saving the backplane bandwidth.
  • The second-level duplication is implemented on the service board. By using the "VLAN+GIP" index, the service board duplicates multicast data to the GPON port interested in the multicast program in an as-per-requirement manner, effectively saving the downstream bandwidth of the GPON port. Then the service board encapsulates and transmits the multicast data on the GPON port in the mode of multicast GEM port (system-level parameter, configurable, default value 4095).
  • The third-level duplication is implemented on the ONT. By using the "VLAN+GMAC" white list, the ONT filters out unneeded multicast data to avoid bandwidth overflow at the downstream ingress (ONT only supports that in olt-control mode). Then, by using the "VLAN+GMAC" index, the ONT duplicates the multicast data to the ONT ports in an as-per-requirement manner (only supports forwarding by using GMAC in snooping mode).
NOTE:
  1. This forwarding mode applies to ASMSSM and ASM ONLY group filter modes (for details, see "Group Filter Mode").
  2. The ONT that implements the third-level duplication is recommended to use the chip that supports VLAN+GIP forwarding. If the ONT does not use such a chip, program GIP-to-GMAC mapping must be a one-to-one mapping. Without the one-to-one mapping on the same ONT, garbled images will occur.
This topic describes only the forwarding framework in the most common single-copy duplication mechanism. For the hardware forwarding framework in the multi-copy duplication mechanism, see "GPON Multi-Copy Duplication."

GPON Multicast Forwarding Table (VLAN+GIP+SIP) [OLT]

Figure 2 GPON multicast forwarding table (VLAN+GIP+SIP)
The OLT supports a distributed 2+1-level duplication architecture:
  • The first-level duplication is implemented on the control board. By using the "VLAN+GIP+SIP" index, the control board duplicates multicast data to the service board interested in the multicast program in an as-per-requirement manner, effectively saving the backplane bandwidth.
  • The second-level duplication is implemented on the service board. By using the "VLAN+GIP+SIP" index, the service board duplicates multicast data to the GPON port interested in the multicast program in an as-per-requirement manner, effectively saving the downstream bandwidth of the GPON port. Then the service board encapsulates and transmits the multicast data on the GPON port in the mode of multicast GEM port (system-level parameter, configurable, default value 4095).
  • The third-level duplication is implemented on the ONT. By using the "VLAN+GMAC" white list, the ONT filters out unneeded multicast data to avoid bandwidth overflow at the downstream ingress (ONT only supports that in olt-control mode). Then, by using the "VLAN+GMAC" index, the ONT duplicates the multicast data to the ONT ports in an as-per-requirement manner (only supports forwarding by using GMAC in snooping mode).
NOTE:
  1. This forwarding mode applies to the SSM ONLY group filter mode.
  2. Due to hardware limitations, only the difference in the least significant 20 bits can be differentiated between source IP addresses (SIPs). For example, 1.1.1.1 and 2.1.1.1 are the same SIP for the device; 1.1.1.1 and 1.1.1.2 are different SIPs for the device.
  3. The ONT that implements the third-level duplication is recommended to use the chip that supports VLAN+GIP forwarding. If the ONT does not use such a chip, program GIP-to-GMAC mapping must be a one-to-one mapping. Without the one-to-one mapping on the same ONT, garbled images will occur.

Multicast Forwarding Table (VLAN+GMAC) [DSLAM]

Figure 3 DSLAM multicast forwarding table (VLAN+GMAC)
The DSLAM supports a distributed two-level duplication architecture:
  • The first-level duplication is implemented on the control board. By using the "VLAN+GMAC" index, the control board duplicates multicast data to the service board interested in the multicast program in an as-per-requirement manner, effectively saving the backplane bandwidth.
  • The second-level duplication is implemented on the service board. By using the "VLAN+GMAC" index, the service board duplicates multicast data to the multicast user (usually corresponding to the first port) interested in the multicast program in an as-per-requirement manner.
NOTE:
This forwarding mode applies to boards that do not support Layer 3 multicast forwarding chip.

Multicast Forwarding Table (VLAN+GIP) [DSLAM]

Figure 4 DSLAM multicast forwarding table (VLAN+GIP)
The DSLAM supports a distributed two-level duplication architecture:
  • The first-level duplication is implemented on the control board. By using the "VLAN+GIP" index, the control board duplicates multicast data to the service board interested in the multicast program in an as-per-requirement manner, effectively saving the backplane bandwidth.
  • The second-level duplication is implemented on the service board. By using the "VLAN+GIP" index, the service board duplicates multicast data to the multicast user (usually corresponding to the first port) interested in the multicast program in an as-per-requirement manner.
NOTE:
This forwarding mode applies to ASMSSM and ASM ONLY group filter modes.

Multicast Forwarding Table (VLAN+GIP+SIP) [DSLAM]

Figure 5 DSLAM multicast forwarding table (VLAN+GIP+SIP)
The DSLAM supports a distributed two-level duplication architecture:
  • The first-level duplication is implemented on the control board. By using the "VLAN+GIP+SIP" index, the control board duplicates multicast data to the service board interested in the multicast program in an as-per-requirement manner, effectively saving the backplane bandwidth.
  • The second-level duplication is implemented on the service board. By using the "VLAN+GIP+SIP" index, the service board duplicates multicast data to the multicast user (usually corresponding to the first port) interested in the multicast program in an as-per-requirement manner.
NOTE:
  1. This forwarding mode applies to the SSM ONLY group filter mode.
  2. Due to hardware limitations, only the difference in the least significant 20 bits can be differentiated between SIPs. For example, 1.1.1.1 and 2.1.1.1 are the same SIP for the device; 1.1.1.1 and 1.1.1.2 are different SIPs for the device.

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