查了下29244，首先一个PDR关联多个URR或QER是合规的。原文是：“Each PDR shall contain a PDI, i.e. one or more match fields against which incoming packets are matched, and may be associated to the following rules providing the set of instructions to apply to packets matching the PDI:
- zero, one or more QERs, which contains instructions related to the QoS enforcement of the traffic;
- zero, one or more URRs, which contains instructions related to traffic measurement and reporting.”
然后后面有章节专门提到了qer和urr的handing。关于一个pdr关联多个urr，个人认为是合理的，只要任意一个满足，upf都需要上报。比如urr1要求上行流量100M上报，urr2要求总流量达到500M时上报。或者是不同类型的urr上报（如一个urr是做start of traffic上报，一个urr是做droped dl traffic threshold上报。）规范里只是举例说明了一个特例，就是当urr1要求upf当配额耗尽后就丢弃用户面数据包，那么其他的urr应该停止测量。原文是：
“A PDR can be associated with multiple URRs. If one of these URRs requires the UP function to drop the user data packets, e.g. when the Quota has been exhausted, the other URRs associated to the PDR need also to stop their measurements, except for URRs including the Measurement Information with the 'Measurement Before QoS Enforcement' flag set to "1".”
A2：是的。N4口只有pdr和qer里会出现qfi，其中pdr出现的qfi只针对上行流量（即source interface=access），用来告诉upf怎么拆包和检测包（而不是用来插入qfi的），也就是告诉upf，如果有n3口的包过来了，并且gtp-u的qfi=X，那么就关联对应的far进行转发。而QER里的QFI则只针对下行流量（也就是source interface=core或者FAR的destination interface=access）的，用于将下行流量往N3转的时候，（gtp-u头）打上对应的QFI。
原文1【For 5GC, the mapping of DL traffic to QoS flows is achieved by configuring QERs with QFI(s) for the QoS flow marking and associating FARs to the downlink PDRs, with FARs set to forward the packets to the appropriate downstream GTP-U tunnel (N9 or N3).
-对于5GC，DL流量到QoS流的映射是通过为QoS流标记配置带有QFI(s)的QER并将FAR与下行链路PDR相关联来实现的，FAR设置为将数据包转发到适当的下游GTP-U隧道（N9或N3）;】
原文2：【Create QER IE within PFCP Session Establishment Request: - QFI：This IE shall be present if the QoS flow identifier shall be inserted by the UPF.
补充：
其实Q2的答案也和Q1有关。就是根据我的发现，只有下行流量的N4规则的PDR里，才会出现两个QER（一个用来MBR，一个用来QFI打标）。您可以观看下看看。上行流量的N4规则没有看到关联两个PDR的情况。这个是我的发现。供您参考。
还有两段原文，也附上：
For 5GC, the PDI may additionally contain one or more QFI(s) to detect traffic pertaining to specific QoS flow(s).
- 这个是说PDI里的QFI是用来做检测，不是用来打标的。
As a result, uplink packets received on the uplink PDU session but that do not match the SDF filter(s) or Application detection filter and QFI associated to the uplink PDRs are discarded.
- 这个是说，没关联上SDF filter 或app-id或QFI的上行包就会被丢弃。
Update QER IE within PFCP Session Modification Request：
- QFI：This IE shall be present if it needs to be modified.
- 这个是说QFI是可以被修改的（和MBR一样）。通过N4会话修改流程。
