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mywiki:gpon [2016/06/20 11:40] – shaoguohmywiki:gpon [2019/09/15 18:55] (current) – external edit 127.0.0.1
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 ====== GEM Format ====== ====== GEM Format ======
 {{:mywiki:gem.png|}} {{:mywiki:gem.png|}}
 +
 +There are 2 types of GEM Channels:
 +
 +    Downstream-only GEM Channels - These channels are used to transmit downstream broadcast/multicast traffic from OLT to all ONTs. The ONTs identify traffic meant for them based on GEM Port ID.
 +    Bi-directional GEM Channels - These channels are used for upstream and downstream traffic between the OLT and the ONT. The frames are transmitted from the OLT into the GPON interface and are forwarded only on the U interface of the ONT on which that GEM Port has been assigned.
 +
  
 PTI Type PTI Type
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 A traffic bearing object within an ONT that represents a group of logical connections, and is treated as a single entity for the purpose of upstream bandwidth assignment on the PON. In the upstream direction, it is used to bear the service traffic. Each T-CONT corresponds to service traffic of one bandwidth type. Each bandwidth type has its own QoS feature. A traffic bearing object within an ONT that represents a group of logical connections, and is treated as a single entity for the purpose of upstream bandwidth assignment on the PON. In the upstream direction, it is used to bear the service traffic. Each T-CONT corresponds to service traffic of one bandwidth type. Each bandwidth type has its own QoS feature.
      
-ALLOC_ID:+**ALLOC_ID**:
  
 Each T-CONT is identified by the ALLOC_ID uniquely. The ALLOC_ID ranges from 0 to 4095. It is allocated by OLT i.e. a T-CONT, and can only be used by one ONT per PON interface on the OLT. Each T-CONT is identified by the ALLOC_ID uniquely. The ALLOC_ID ranges from 0 to 4095. It is allocated by OLT i.e. a T-CONT, and can only be used by one ONT per PON interface on the OLT.
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 A GPON Encapsulation Method (GEM) port is a virtual port for performing GEM encapsulation for transmitting frames between the OLT and the ONT. Each different traffic-class (TC) per UNI is assigned a different GEM Port. Each T-CONT consists of one or more GEM Ports. Each GEM port bears one kind of service traffic i.e. a T-CONT type. A GPON Encapsulation Method (GEM) port is a virtual port for performing GEM encapsulation for transmitting frames between the OLT and the ONT. Each different traffic-class (TC) per UNI is assigned a different GEM Port. Each T-CONT consists of one or more GEM Ports. Each GEM port bears one kind of service traffic i.e. a T-CONT type.
  
-GEM Port ID:+**GEM Port ID**:
  
 Each GEM Port is identified by a port ID uniquely. The Port ID ranges from 0 to 4095. It is allocated by the OLT, i.e. a GEM port, and can only be used by a single ONT per PON interface on the OLT. Each GEM Port is identified by a port ID uniquely. The Port ID ranges from 0 to 4095. It is allocated by the OLT, i.e. a GEM port, and can only be used by a single ONT per PON interface on the OLT.
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 {{:mywiki:upstream-framing-structure1-1024x496.jpg|}} {{:mywiki:upstream-framing-structure1-1024x496.jpg|}}
 +
 +{{:mywiki:gpon_up_traffic.png|}}
  
 ====== Downstream Frame structure ====== ====== Downstream Frame structure ======
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     S-start，S-stop：start and stop times (16bits fields, in Bytes from beginning of US frame)     S-start，S-stop：start and stop times (16bits fields, in Bytes from beginning of US frame)
     CRC：CRC(cyclic redundancy check) Checksum.     CRC：CRC(cyclic redundancy check) Checksum.
 +    
 +{{:mywiki:pon_down_traffic.png|}}   
 +
 +====== VLANs and GEM Ports ======
  
 +https://sites.google.com/site/amitsciscozone/home/gpon/gpon-vlans-and-gem-ports
  
  
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 | RTD | Round Trip Delay | | RTD | Round Trip Delay |
 | RTT | Round Trip Time | | RTT | Round Trip Time |
 +| SerDes | Serializer/Deserializer pronounced sir-deez |
 | SFU | Single Family Unit | | SFU | Single Family Unit |
 | SBU | Single Business Unit | | SBU | Single Business Unit |
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