• A Switch is permitted to maintain a local PTM context for use in fulfilling PTM Requests received on its Downstream Ports. • A Switch which is not acting as a PTM Root must invalidate its local context no more than 10 ms from the last PTM dialog on its Upstream Port. The Switch must then refresh its local PTM context prior to issuing further PTM ResponseD Messages on its Downstream Ports. This requirement for periodic refreshes is optional if it is guaranteed by implementation-specific means that the Switch’s local clock is phase locked with PTM Master Time. • Any Switch implementing a local clock for the purpose of maintaining a local PTM context must report the granularity of this clock as defined in the PTM Capabilities structure (Section 7.9.16 ). 翻译

• 交换机可以维护本地 PTM 上下文，用于满足其下行端口接收的 PTM 请求。
• 不作为 PTM 根的交换机必须在其上行端口上的最后一次 PTM 对话后不超过 10 毫秒无效化其本地上下文。然后，交换机必须在其下行端口上发出进一步的 PTM ResponseD 消息之前刷新其本地 PTM 上下文。如果实现特定的方法保证了交换机的本地时钟与 PTM 主时间相位锁定，则可以选择不定期刷新的要求。
• 为了维护本地 PTM 上下文而实现本地时钟的任何交换机都必须将该时钟的粒度报告为 PTM 能力结构（第 7.9.16 节）中定义的粒度。

相关问题

In addition to the requirements listed above for the PTM Requester and PTM Responder Roles, Switches must follow these requirements: • When the Upstream Port is associated with a Multi-Function Device, only a single Function associated with that Upstream Port is permitted to implement the PTM Extended Capability structure. For Switches, all PTM functionality associated with the Switch must be controlled through that structure. It is not required that the Function implementing the PTM Extended Capability structure be the Switch Upstream Port Function. • The PTM Extended Capability structure for a Switch must indicate support for both the PTM Requester and PTM Responder roles. • The PTM Extended Capability in the Upstream Port controls all Switches in that Upstream Port. • A Switch is permitted to act as a PTM Root, or to issue PTM Requests on its Upstream Port to obtain the PTM Master Time for use in fulfilling PTM Requests received at its Downstream Ports. In the latter case the Switch must account for any internal delays within the Switch. 翻译

除了 PTM 请求者和 PTM 响应者角色的要求之外，交换机必须遵循以下要求：
• 当上行端口与多功能设备相关联时，只允许与该上行端口相关联的单个功能实现 PTM 扩展能力结构。对于交换机，所有与交换机相关的 PTM 功能必须通过该结构进行控制。实现 PTM 扩展能力结构的功能不必是交换机上行端口功能。
• 交换机的 PTM 扩展能力结构必须指示支持 PTM 请求者和 PTM 响应者角色。
• 上行端口中的 PTM 扩展能力控制该上行端口中的所有交换机。
• 交换机可以作为 PTM 根，或者在其上行端口发出 PTM 请求以获取用于满足其下行端口接收的 PTM 请求的 PTM 主时间。在后一种情况下，交换机必须考虑交换机内部延迟。

• Support for the PTM Responder role is indicated by setting the PTM Responder Capable bit in the PTM Capability register. • Switches and Root Complexes are permitted to implement the PTM Responder Role. ◦ A PTM capable Switch, when enabled for PTM by setting the PTM Enable bit in the PTM Control register associated with the Switch Upstream Port, must respond to all PTM Request Messages received at any of its Downstream Ports. ◦ The mechanism by which Root Complexes communicate PTM Master Time to RCiEPs is implementation specific. 翻译

• 支持 PTM Responder 角色需要在 PTM Capability 寄存器中设置 PTM Responder Capable 位。 • Switches 和 Root Complexes 允许实现 PTM Responder 角色。 ◦ PTM capable Switch，在通过设置与 Switch Upstream Port 相关的 PTM Control 寄存器的 PTM Enable 位启用 PTM 后，必须响应其所有 Downstream Ports 收到的所有 PTM Request Messages。 ◦ Root Complexes 将 PTM Master Time 传递给 RCiEPs 的机制是实现特定的。