More inline.
-----Original Message-----
From: Charlie Perkins [mailto:charles.perk...@earthlink.net]
Sent: Monday, January 22, 2018 2:27 PM
To: Bertz, Lyle T [CTO] <lyle.t.be...@sprint.com>
Cc: dmm@ietf.org
Subject: Re: [DMM] Parent versus child mobility context
Hello Lyle,
More follow-up inline. We're getting closer.
On 1/22/2018 11:27 AM, Bertz, Lyle T [CTO] wrote:
Hello Lyle and all,
I think I agree with most of what you say below. I'm concerned with how to
organize the information in the model. So, for that purpose, please verify
whether my following understandings are correct.
- The mobility context resides on a DPN.
- The mobility context provides necessary information (e.g., QoS) for a single
mobile node.
- The DPN uses it to manage data-plane traffic for that mobile node.
This may be too broad of a view. What about a mobile node with
multiple mobility sessions? In such a case it may be managing one or
more (but not necessarily all of) the mobile node's mobility
sessions
Yes. This is why I did not put "all" between "manage" and "data-plane".
LB > Ok. We should probably be more explicit though for the casual observer if
this language is used in the specification.
In my earlier email on this subject, I was using Mobility Context as describing something
more associated with a mobile node, than with a particular flow. If you want it to mean
"bearer", then we ought to call it a Bearer.
Maybe it would be easier to understand if we had something called a "Mobile-Node Context", and in
that context we had a set of Bearer Contexts (or, just Bearers). Each bearer would inherit from the Mobile
Node context simply by being part of it. The Mobile Node context (serving as "parent") would
determine max bandwidth, IP address, etc. Back in the old days, we also defined security aspects and some
other factors, as part of what FPC would call the "mobility context".
We have several concepts that have hierarchy, e.g. Service Level (sr-id or APN
- apn-oi if I recall), device level, Mobility Session, bearers, flow based
filters (effectively living within a bearer).
There isn't anything about Service Level in the first part of the document, and I did not
find anything about Service-ID that referenced mobility context. Mobility Context does
not define Service Level. Similarly for APN. The string "-oi" does not occur
in the document.
Device level is a mystery to me.
Now, this isn't to say that your comment is irrelevant. But, at minimum, the
relevance is not spelled out in the current document.
LB> Ack. They are not mentioned these in the documents; I was merely providing
examples.
We also have the 5G concepts as well.
We have, in fact, an infinitude of mutually contradictory 5G concepts.
I might suggest that they look at Mobile IP, which was designed exactly
to provide high-speed, low-latency, application-independent mobility
management. But, I digress.
LB> I am in agreement here but I believe that as Release 15 is finalized in
3GPP we will see clarity. My question would be if other next generation standards
/ technologies follow so that we have a tractable problem space but I too, digress.
The one thing that is obvious is that the idea of hierarchy applies whether
it is pacers/shapers, bearers or filters that apply some charging / gating /
marking. A light touch of lifecycle (fate sharing) amongst the hierarchy,
data does not need to be repeated within the hierarchy and building the data
structure by requiring a parent id if it was a child (implying the parent must
exist!) was the best we could do without necessarily making decisions that may
appear to preclude a specific set of mobile network technologies.
We certainly agree on the existence of hierarchy pervading our problem
space. And on the need to consider fate-sharing for between mobile-node
authorizations and allocated bearers. But my suggested approach of
having the Bearers delineated under an inclusive Mobility Context
provides for that in a natural way. Perhaps the word "bearer" shows too
much bias towards 3GPP, in which case we could simply use "mobility
session" or "flow".
LB> Ack. I think I would object to the use of Bearer. Flow(s) may be too
granular. Maybe a verbal delineation between a Flows-Context (implying 1 or more)
and some other concept such as Session-Context (old terminology) or
Mobility-Context. imo though it may be more beneficial to state it as a context
type and imply some hierarchy?
============ end of my follow-up for this email ===================
Regards,
Charlie P.
If you really want to maintain Parent Context and Child Context as independent
structure elements, then we need to make a new indexed set for them.
We just used a pointer from a Context to a Parent Context. If the value was
non-empty it was a child and the parent Id must point to a valid Context.
Regards,
Charlie P.
On 1/22/2018 5:30 AM, Bertz, Lyle T [CTO] wrote:
++ mailing list
I agree with you Marco.
Keeping the parent/child relation is crucial. Although we often cite
dedicated vs. default bearers (LTE) we need to also ack that we use
hierarchical concepts throughout mobility and forwarding management protocols,
e.g. meters, session and sub-session (includes accounting), etc.
Lifecycle association here (fate sharing of the children with the parent) is an
important concept. Many of the mobility systems assume gateways (LMAs and
MAGs) have knowledge of the relationships between sessions and sub-session and
will often kill the session in order to reduce signaling overhead. They also
assume when installing a session / sub-session that any violation of hierarchy
rules, e.g. setting a child's max bit rate above a parent's, would be properly
enforced, i.e. it is an error or the child's value is ignored.
For FPC we also use it to avoid sending redundant data (does one need
to send the mobile's IP address for any sort of sub-session work if it
is tied to a parent that already has it?)
-----Original Message-----
From: Marco Liebsch [mailto:marco.lieb...@neclab.eu]
Sent: Monday, January 22, 2018 5:49 AM
To: Charlie Perkins <charles.perk...@earthlink.net>; Bertz, Lyle T
[CTO] <lyle.t.be...@sprint.com>
Cc: Satoru Matsushima <satoru.matsush...@gmail.com>; Sri Gundavelli
(sgundave) <sgund...@cisco.com>; Moses, Danny <danny.mo...@intel.com>;
Weaver, Farni [CTO] <farni.wea...@sprint.com>; Matsushima Satoru
<satoru.matsush...@g.softbank.co.jp>
Subject: RE: Parent versus child mobility context
That has been introduced to reflect e.g. dedicated bearers which come on top of
default bearers hence have some level of dependency. If context associated with
a default bearer gets closed, dependent context will follow. To me it makes
sense. Others?
marco
-----Original Message-----
From: Charlie Perkins [mailto:charles.perk...@earthlink.net]
Sent: Montag, 22. Januar 2018 06:29
To: Bertz, Lyle T [CTO]
Cc: Marco Liebsch; Satoru Matsushima; Sri Gundavelli (sgundave);
Moses, Danny; Weaver, Farni [CTO]; Matsushima Satoru
Subject: Parent versus child mobility context
Hello folks,
I have looked at this several times, and I would like to propose simplifying it
to simply be a mobility context. I don't see that the extra complication is
worth it, especially right now. If, in the future, we need it for something,
we could put it back in.
Thanks for your consideration of this request.
Regards,
Charlie P.
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