Hello all,
Some questions have come up in recent meetings of IEEE 1588 and IEEE 802.1
working groups that are relevant to the TICTOC project
draft-ietf-tictoc-1588v2-yang. I would like to get some feedback from TICTOC to
help determine if a change is needed for draft-ietf-tictoc-1588v2-yang.
1588-2008 has the concept of a "port", and for a 1588 product with two or more
ports, 1588 specifies the transfer of time between these ports. The 1588-2008
specifications for the port are "logical", in that they are independent of any
specific transport or media. For example, the 1588 port can use a layer-2 802
mapping, or the port can use a UDP mapping.
When a 1588-2008 product is managed (such as with YANG), the management client
is likely to ask:
How do I find the "real" port that a 1588 "logical" port is using?
For example, if the UDP mapping is used, I might want to find relevant IP
addresses, and then go down in the data models to find relevant MAC addresses,
802.3 link speeds, and so on.
The current consensus in the 1588 working group is that although this question
is important, since 1588 is transport-independent, the answer cannot be fully
specified in the 1588 data sets (i.e. information model). The actual management
data model (e.g. YANG, MIB, 1588 management protocol) potentially has better
connections to the "real" port, and therefore 1588 defers this topic to each
management data model. In other words, the 1588 standard itself will not fully
answer this question, but the YANG (i.e. draft-ietf-tictoc-1588v2-yang) is
expected to answer the question to the best of its ability.
This question came up in a recent discussion in IEEE 802.1, relative to their
profile of 1588, 802.1AS. Refer to slide 5 of:
http://www.ieee802.org/1/files/public/docs2017/as-gutierrez-yang-0317-v01.pdf
This presentation suggests that the 1588 port (called a "TAS port" in 802.1AS)
should be done as an augment of the RFC7223 interface.
The current consensus in IEEE 802.1 is that their profile 802.1AS will defer to
the 1588 YANG module (draft-ietf-tictoc-1588v2-yang) for this decision. The
YANG module for 802.1AS will augment the 1588 YANG module as described at the
end of section 1 of draft-ietf-tictoc-1588v2-yang.
So... I think we need to select from one of three options for
draft-ietf-tictoc-1588v2-yang:
Option 1: 1588 port augments RFC7223 interface
--
Although this is a reasonable suggestion, it works under the assumption that a
1588 port "is a type of" RFC7223 interface. That implies that the 1588 port has
a place in the interface stack represented by higher-layer-if and
lower-layer-if.
I would argue that a 1588 port "uses" an RFC7223 interface, and the 1588 port
does not belong in the interface stack. 1588 is a higher-layer protocol, and in
that respect, it is more analogous to protocols like TCP and UDP, and not the
protocols listed in iana-if-type.yang.
If we decide to implement this option, we need to do it in the first 1588 YANG
(draft-ietf-tictoc-1588v2-yang). I assume that we cannot change the 1588 port
from non-augment to augment in a future revision of the 1588 YANG.
Option 2: 1588 port contains a reference to an RFC7223 interface
--
1588 requires a configured interface for each 1588 port. By using interface-ref
instead of an interface augment, this establishes the relationship as "uses".
This would be added to draft-ietf-tictoc-1588v2-yang as a new leaf in grouping
port-ds-entry, such as:
leaf interface-reference {
type if:interface-ref;
description
"Reference to the configured interface that is used by
this PTP Port (see RFC 7223).";
}
This enables the management client to find the interface that the 1588 (PTP)
port is using. The management client can also traverse up/down the interface
stack to find additional information.
Option 3: Do nothing in draft-ietf-tictoc-1588v2-yang
--
This is what we have so far.
Presumably a future revision of the 1588 YANG could decide to implement option
2, but not option 1.
Question: Which option should we use for draft-ietf-tictoc-1588v2-yang?
--
I recommend option 2.
Previously I was fine with option 3, but since this is an open question in the
1588 community, it is best to resolve it in the first 1588 YANG module.
At a minimum, we need to decide if we are doing option 1, because that decision
cannot be changed in future 1588 YANG module revisions.
This decision is not related to the 1588 data set specifications (2008 or
future), because current 1588 consensus is that it is entirely within the scope
of the 1588 YANG module.
Thanks everyone,
Rodney Cummings
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