Hi Doug, TC are not supposed to change source IP address of delay requests.
If the TC is a layer2 switch/bridge, it must not modify the source MAC address while forwarding and must never touch the layer3 addresses. If the TC is a layer3 IP router, it must not modify the source IP address while forwarding and must change the source MAC address to the MAC address of its egress port. If the TC is a layer4 device, e.g., a NAT device, it modifies the source IP address of messages as it is its functionality. It may be the case that such functionality is required in the enterprise. My point is that it is far from obvious and the draft needs to elaborate why it's needed. >> This is required by the standards that specify the transport networks. I would appreciate if you point to the relevant standards. The draft states that additional support is required for this deployment scenario: "For this deployment scenario timeTransmitters will need to have configured tables of timeReceivers' IP addresses and associated Clock Identities in order to send Delay Responses to the correct PTP Nodes" These tables would be part of the IEEE1588 spec if this TC behavior was standard. It is not trivial to add support for these tables in HW, if you want to support scale and speed. Best, Ron From: Doug Arnold <[email protected]> Sent: Wednesday, May 22, 2024 12:36 AM To: Ron Cohen <[email protected]>; [email protected] Subject: [EXTERNAL] Re: Enterprise Profile: Support for Non standard TCs Prioritize security for external emails: Confirm sender and content safety before clicking links or opening attachments ________________________________ Hello Ron, Yes. A TC is required to change the source address of a message at least for Ethernet and IP mappings. This is not an IEEE 1588 decision. This is required by the standards that specify the transport networks. Ethernet (IEEE 802.1Q) IPv4 and IPv6. A TC effectively changes the payload of the messages from the point of view of L2 and L3, so it is a new frame and new packet to those layers. I think that IPv4 has an option to alter a message in-route, but the node is supposed to zero out the source address. Regards, Doug ________________________________ From: Ron Cohen <[email protected]<mailto:[email protected]>> Sent: Tuesday, May 7, 2024 12:43 PM To: [email protected]<mailto:[email protected]> <[email protected]<mailto:[email protected]>> Subject: [TICTOC]Enterprise Profile: Support for Non standard TCs Hi, I'm late to the game here. I apologize in advance if this has already been discussed and decided: I can't figure out why the profile needs to support non-standard TCs, or what seems to be a strange combination of a NAT+TC devices: "In PTP Networks that contain Transparent Clocks, timeTransmitters might receive Delay Request messages that no longer contains the IP Addresses of the timeReceivers. This is because Transparent Clocks might replace the IP address of Delay Requests with their own IP address after updating the Correction Fields. For this deployment scenario timeTransmitters will need to have configured tables of timeReceivers' IP addresses and associated Clock Identities in order to send Delay Responses to the correct PTP Nodes." Is a standard TC allowed to change the source IP address of messages? There should be a strong reason to require support for such devices in a standard profile. Best, Ron /* * Ron Cohen * Email: [email protected]<mailto:[email protected]> * Mobile: +972.54.5751506 */
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