Re: [TICTOC] PTP Enterprise Profile draft

[John Fletcher <[e-mail]>]

Some comments on draft-ietf-tictoc-PTPenterpriseprofile-02

General
In many places the terms "Slave Clock" and "Master Clock" are used.  A clock is not a slave or master.  Slave and Master are two of the several possible states that a Port may be in.
You do not specify that Announce messages shall be sent multicast in all modes.

Title and Abstract:
"Precise Time Protocol" should be "Precision Time Protocol"

Abstract:
"The profile uses ... and allows ..."

Introduction:
Re. BMCA - More correct to which Port shall be the active sending time source.  Master not Grandmaster.

Technical Terms:
Acceptable Master List - should be "Acceptable Master Table"
Best Master Clock Algorithm - "... properties each Master Capable Clock sends in its Announce Message" - Announce messages are only sent by Ports in Master state; they are not sent by other Master-capable Ports.
Ordinary Clock - The definition is different from that in 1588-2008.  The key point is that it has only one port.  It may be slave-only.
Rogue Master - should be "A PTP clock operating with a Port in Master state even though the port should not be in Master state according to the Best Master Clock Algorithm"
Slave Only Clock - should be "An Ordinary Clock whose Port cannot enter the Master state"
Unicast Discovery - You are mixing up "Unicast message negotiation" (1588-2008 clause 16.1) with "Unicast discovery" (1588-2008 clause 17.5)

Network Topology
"... treated as separate PTP systems" should be "... treated as separate PTP communication paths".  See 1588-2008 clause 6.7.1.5

Default Message Rates
"Announce Timeout" should be "Announce Receipt Timeout".
Given that Announce Interval is fixed, the Announce Receipt Timeout should be uniform throughout a domain.  See 1588-2008 clause 7.7.3.1

Requirements for Slave Clocks (ports in Slave state)
Remember that the BMCA is for each port to decide what state it should be in (Master, Slave, Passive etc.).  It is not about a Slave deciding which Master to synchronize to.  Application of BMCA when using Alternate Master Table is already specified in 1588-2008 clause 17.6.2

Management Messages
Why forbid multicast messages?  Some Management Messages are intended for all Ports.

Forbidden PTP Options
Why forbid Alternate Timescales?  Transmission of "local wall clock time", for example, may be a useful feature in the Enterprise environment.



Regards,
John Fletcher



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