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<blockquote>
 GPON: VLANs and GEM Ports
 
 This article discusses traffic flows in GPON. As discussed in GPON
 Fundamentals article, the OLT is the first aggregation point in GPON
 access network. The OLT terminates the GPON Transmission Convergence
 (GTC) layer on the user side and forwards Ethernet frames to Ethernet
 layer on the network side. Figure 1 shows the termination points for
 ONU/ONT scenario.
 
 <a href="https://i.stack.imgur.com/3uQ3b.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3uQ3b.png" alt="enter image description here"></a>
 
 The U reference point represents the customer-facing interface of
 the ONU/ONT. It is possible that the U reference point can be within
 the ONU/ONT device when ONT and RG devices are combined into a single
 device.
 
 The R/S reference point represents the OLT facing ONT interface.
 The S/R reference point represents the Optical Distribution
 Network (ODN) connecting GPON interface on the OLT. The S/R and R/S
 interfaces contain all the protocol elements necessary to allow
 communication between OLT and one or more ONTs over ODN. 
 
 The V reference point represents the network-facing interface of
 the OLT.
 
 Relationship between T-CONT and GEM Ports
 
 Definitions:
 
 T-CONT: A traffic bearing object within an ONU/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 a service traffic of one bandwidth type. Each
 bandwidth type has its own QoS feature.
 
 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
 can only be used by one ONU/ONT per PON interface on the OLT.
 
 GEM Port: A GPON Encapsulation Method (GEM) port is a virtual port for performing GEM encapsulation for transmitting frames between the
 OLT and the ONU/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: 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 can only be used by a single ONU/ONT per PON interface on the
 OLT.
 
 Figure 2 shows the relationship between T-CONT and GEM Ports.
 
 <a href="https://i.stack.imgur.com/tZcfV.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tZcfV.png" alt="enter image description here"></a>
 
 Between the ONT and OLT is the ODN, and Ethernet frames are carried
 over it through the use of GEM Channels. GPON has GEM channels as part
 of its GTC layer. The GEM channels carry variable-length Ethernet
 frames. GEM channels are identified by GEM Port IDs. This identifier
 is assigned by OLT upon creation of a new channel and is only valid
 during the entire life-cycle of the channel. Each GPON interface for a
 given ONT can have several GEM Ports. A GEM Port ID is unique per GPON
 interface and represents a specific traffic or group of flows between
 the OLT and the ONT. 
 
 There are 2 types of GEM Channels:
 
 <ul>
 <li>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.</li>
 <li>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.</li>
 </ul>
 
 GEM Ports are used to differentiate among traffic classes (TCs). A U
 interface may have several GEM Ports associated with it that support
 different TCs. Thus, within a GPON interface, each GEM Port carries
 one or more traffic flows associated with a specific TC.
 
 On U interface, traffic is classified into VLANs with various Ethernet
 priorities based on: Physical Port, VLAN ID, 802.1p bits, &amp;/or DSCP.
 Once the traffic has been assigned a VLAN and COS (802.1p) values,
 these two values are used to select an upstream GEM Port so that QoS
 can be applied to the flows carried by the GEM Port. A GEM Port always
 belongs to a single T-CONT. In downstream direction, the ONT forwards
 the traffic received by GEM Ports to appropriate U interface.
 
 QoS and Traffic Management
 
 As seen from figure 1, the GPON link connects the OLT and ONTs to
 transport Ethernet services. Please note that GPON can also
 encapsulate ATM and TDM (E1, E3) services. The GTC Adaptation sublayer
 maps Ethernet frames into GPON GEM frames. A QoS mechanism is required
 in GEM to support Ethernet QoS (i.e. 802.1p bits). In order to provide
 QoS, two mechanisms are employed:
 
 <ul>
 <li>Classification of traffic into traffic classes</li>
 <li>Forwarding the traffic classes into GEM Ports and T-CONTs configured to emulate Ethernet QoS service</li>
 </ul>
 
 Upstream Traffic Management
 
 Figure 5 shows a sample model of upstream traffic management. It shows
 4 T-CONTs per PON interface where each T-CONT represents a specific
 traffic class (TC). The Classifier receives traffic from U interface
 and maps to queues as per configuration using associated GEM Ports. If
 a second UNI interface is present on the same ONT, it would also
 perform classification and map the traffic to TC(s). As mentioned
 above, a GEM Port must bear one or more T-CONTs. Other upstream
 traffic from other ONTs is mapped to other 4 T-CONTs according to the
 TC. 
 
 At the OLT, each TC is mapped into a separate queue. T-CONTs from
 various ONTs that share the same TC are mapped to the same queue, and
 a scheduler is used among the queues towards the network-facing port
 i.e. V interface.
 
 <a href="https://i.stack.imgur.com/pTF10.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/pTF10.png" alt="enter image description here"></a>
 
 Downstream Traffic Management
 
 Figure 6 shows a sample model of downstream traffic management. In
 downstream direction, T-CONT is not used. Traffic received from the V
 interface at the OLT is assigned to queues according to the TCs. It is
 then transmitted in the downstream direction to the PON interface by
 using a scheduler. At the ONT, the traffic is classified again and
 placed into appropriate queues for each U interface. A scheduler is
 used to transmit frames to the U interface.
 
 <a href="https://i.stack.imgur.com/qcz2t.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qcz2t.png" alt="enter image description here"></a>
</blockquote>

Source and more information:
<a href="https://sites.google.com/site/amitsciscozone/home/gpon/gpon-vlans-and-gem-ports" rel="nofollow noreferrer">https://sites.google.com/site/amitsciscozone/home/gpon/gpon-vlans-and-gem-ports</a>

What I mean with my question is: every ISP gives each client a X speed, like 100 Mbps, 400 Mbps, etc. In DOCSIS technology, they can set the speed limit on the ISP Router, so I have no doubts how they limit client speeds on DOCSIS.. But on FTTH/GPON the architecture is very different, and the ISP router doesn't have any limitation (clients can even use their own router), so the speed limitation is made ISP side... 

<a href="https://i.stack.imgur.com/uYoOT.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/uYoOT.png" alt="enter image description here"></a>

The thing is: how they limit each client speed, if each OLT port handles many clients (normally splitted in 32), and all the network equipments between the OLT and client ONT are passive (splitters)? 
That means the network traffic of at least 32 clients is aggregated in one, before it's handled by 1 OLT port... 

Is it limited ONT side?

Thanks!

How ISP limits subscriber speed on GPON/FTTH (GPON Architecture technical question)

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我的意思是，每个ISP给每个客户一个X速率，比如100 Mbps，400 Mbps等等。在DOCSIS技术中，他们可以对ISP路由器设置速度限制，所以我毫不怀疑他们如何限制DOCSIS上的客户端速度。但在FTTH/GPON上，其体系结构有很大的不同，ISP路由器没有任何限制(客户甚至可以使用自己的路由器)，因此速度限制是ISP方面的。📷问题是:如果每个OLT端口处理多个客户机(通常划分为32)，

问ISP如何在GPON/FTTH (GPON体系结构技术问题)上限制用户速度
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问ISP如何在GPON/FTTH (GPON体系结构技术问题)上限制用户速度EN