Re: [802.21] [DNA] Prefix information for link identification in DNA
Hi Yoshihiro,
I definitely don't mean to contradict what I wrote yesterday. I still think of
the PoA as a link endpoint.
Your comment rightly brings up the necessity of providing a clear definition of
"link" since link and PoA are tightly inter-related.
With a generic definition of PoA as a link endpoint, defining "L2 PoA", "L3
PoA", and "MIH PoA" implies corresponding definitions of "L2 link", "L3 link",
and "MIH link".
I assume from now on that a layer-agnostic notion of link is accepted and that
"link" is not strictly a Layer-2 notion. The group can debate if this is a valid
assumption. If not (i.e., the group prefers to assign a strong L2 flavor to
"link"), we can find a better term (e.g., "connection", or "relationship") and
base on the new term both the generic and the specific definitions of PoA. In
this latter case, "link" would be synonymous of "L2 connection" (or "L2
relationship", or whatever other term the group may identify).
I can think of the following generic definition for a layer-agnostic link:
"Communication relationship for the exchange of messages between adjacent peer
protocol entities."
Where:
"Peer protocol entities" always belong to the same protocol layer (e.g., L2, L3,
MIH).
"Adjacent" emphasizes that there is no other interposed peer entity between the
ones that terminate the link (e.g., there cannot be another L3 entity between
the endpoints of an L3 link; if such entity is present, there are two and not
one L3 links). This does not prevent a link from having more than two endpoints:
in a multicast link, for example, all endpoints are adjacent to each other and
none of them is necessary to enable connectivity between others.
The layer-specific definitions easily follow:
L2 link: "Communication relationship for the exchange of L2 messages between
adjacent L2 entities."
L3 link: "Communication relationship for the exchange of L3 messages between
adjacent L3 entities."
MIH link: "Communication relationship for the exchange of MIH messages between
adjacent MIH entities."
Having the notions of "L2 link", "L3 link", and "MIH link" in place, the PoA
definitions I previously proposed can easily be mapped as follows:
L2 PoA: network-side endpoint of L2 link involving the UE
L3 PoA: network-side endpoint of L3 link involving the UE
MIH PoA: network-side endpoint of MIH link involving the UE
As for identifying the endpoint entity as part of a network node:
The L2 PoA is an L2 interface on the network node, identified by an L2 address.
The L3 PoA is an L3 interface on the network node, identified by an L3 address
(on a router, the same physical interface can co-locate L2 and L3 interfaces).
The MIH PoA is an MIH interface on the network node, i.e., an interface (either
L2 or L3) with which the MIH function of the network node is registered for any
of the MIH services. When referring to both transport and MIH capabilities of
the interface, we may have an "L2 MIH PoA" or an "L3 MIH PoA".
The main purpose of the endpoint vs. node distinction in the PoA definition is
to avoid ambiguities when the same network node can terminate multiple links and
present for each of them different capabilities and behaviors (i.e., MIH
capability can be activated on one interface and not on another, or the node can
be a hybrid L2/L3 box with both L2 ports and L3 ports). Defining the PoA with
respect to a specific link (or connection) brings the focus of the PoA
definition on the functionality that the corresponding UE can obtain from that
point in the network, without requiring any unnecessary assumptions on the
overall nature of the network node that includes it.
While I am sure that the wording for the definitions I am proposing can be
dramatically improved, I am convinced of the absolute necessity to single out
the respective entities and provide clear definitions for each of them.
Thanks,
Andrea
Yoshihiro Ohba wrote:
>
> Andrea,
>
> The PoA definition below is going to the direction that the notion of
> PoA is less associated with the notion of "link", as opposed to what
> you made in your previous general statement which I have fully agreed.
> Or you may be introducing a new definition of "link" as "a specific
> type of communication relationship", which seems to be too ambiguous.
>
> Yoshihiro Ohba
>
> On Fri, Sep 30, 2005 at 11:25:04AM -0400, Andrea Francini wrote:
> > Trying to finalize one part of the ongoing discussion: the PoA definition.
> >
> > I have the impression that some people consider the capability of supporting MIH
> > as part of the definition of PoA, while other people don't, giving it only a
> > network connectivity value.
> >
> > What about the following:
> >
> > 1. General definition of PoA:
> >
> > a. "PoA is the first point in the network that acts as the UE counterpart for a
> > specific type of communication relationship (e.g., L2, L3, MIH)."
> >
> >
> > 2. Accordingly, the following three specific definitions could be added:
> >
> > b. "L2 PoA is the network-side endpoint of the L2 link by which the UE connects
> > to the network."
> >
> > c. "L3 PoA is the closest network counterpart for the UE that requires an L3
> > address to be identified in UE-generated messages."
> >
> > d. "MIH PoA is the closest network counterpart of the UE for MIH exchanges."
> >
> >
> > Thanks,
> >
> > Andrea
> >
> >
> > "Stefano M. Faccin" wrote:
> > >
> > > Peretz, nobody denies that. The issue here is that what you have been saying doe not allow for deployments that do not use any MIH services at L2. Even if you may not believe these deployments will happen, there are vendors and operators that do believe that their networks will only use MIH services at L3, at least for the initial deployments. Thjerefore our model and definitions must allow for this. In this model, there is no MIH @ L2, and the PoA is in the subnet where the UE gets its IP address.
> > > Stefano
> > >
> > > ________________________________
> > >
> > > From: ext Peretz Feder [mailto:pfeder@LUCENT.COM]
> > > Sent: Fri 9/30/2005 10:06 AM
> > > To: STDS-802-21@listserv.ieee.org
> > > Subject: Re: [802.21] [DNA] Prefix information for link identification in DNA
> > >
> > > "I do not understand how any one would conclude that the MIH services are only between UE and the AP/BS."
> > >
> > > The discussion is PoA and not services. The 1st PoA could be L2 for IS and CS. With no PoA at L2, the poor UE will have no MIH services until IP is established. The performance will be very different, not to mention a UE with a bridging only attributes, such as 802.16 terminal with only Ethernet CS (no IP CS).
> > >
> > > Nobody is saying MIH services are strictly between UE and BS. Performance will be better when PoA L2 MIH is established.
> > >
> > > Peretz
> > >
> > > On 9/30/2005 10:50 AM, Srinivas.Sreemanthula@nokia.com wrote:
> > >
> > > The MIIS is provisioned between MIH in UE to a network counter part any
> > > where in the network. This network node can either act as a proxy info
> > > server or an info server. We also identified MIIS requires L3 and hence
> > > the WG went through the exercise of identifying all the UL requirements
> > > and establish coordination with IETF. However, in that discussion, there
> > > was no reference to whether the AP/BS was MIH or non-MIH capable.
> > >
> > > Even if we leave out the info services from the discussion, I do not
> > > understand how any one would conclude that the MIH services are only
> > > between UE and the AP/BS.
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: ext Peretz Feder [mailto:pfeder@lucent.com]
> > > Sent: Friday, September 30, 2005 9:39 AM
> > > To: Sreemanthula Srinivas (Nokia-NRC/Dallas)
> > > Cc: STDS-802-21@listserv.ieee.org
> > > Subject: Re: [802.21] [DNA] Prefix information for link
> > > identification in DNA
> > >
> > > Are you indicating attaching to a non MIH enabled AP/BS and
> > > receiving MIH IS over R4 from a remote MIH info server?
> > >
> > >
> > > On 9/30/2005 10:27 AM, Srinivas.Sreemanthula@nokia.com wrote:
> > >
> > >
> > >
> > > Did we miss the whole discussion of MIH information services?
> > >
> > >
> > > ________________________________
> > >
> > > From: ext Peretz Feder [mailto:pfeder@LUCENT.COM]
> > > Sent: Friday, September 30, 2005 9:16 AM
> > > To: STDS-802-21@LISTSERV.IEEE.ORG
> > > Subject: Re: [802.21] [DNA] Prefix information for link
> > >
> > >
> > > identification
> > >
> > >
> > > in DNA
> > >
> > >
> > > "you have first to be very clear about what you're attaching"
> > >
> > > I would think that in 802.21, we first attach the UE's
> > >
> > >
> > > MIH to a BS/AP
> > >
> > >
> > > that supports MIH capability.
> > >
> > > On 9/30/2005 8:55 AM, Stefano M. Faccin wrote:
> > >
> > >
> > > Mike, well said!
> > > Stefano
> > >
> > > ________________________________
> > >
> > > From: ext Mike Moreton [mailto:mm2006@MAILSNARE.NET]
> > > Sent: Fri 9/30/2005 3:09 AM
> > > To: STDS-802-21@listserv.ieee.org
> > > Subject: Re: [802.21] [DNA] Prefix information for link
> > > identification in DNA
> > >
> > >
> > >
> > > To extend (I think!) Stefano's point, before
> > >
> > >
> > > determining what the PoA
> > >
> > >
> > > is, you have first to be very clear about what you're
> > >
> > >
> > > attaching. Just
> > >
> > >
> > > saying "the terminal" makes no sense, because different layers in the
> > > terminal's protocol stack attach to different places in the network.
> > >
> > > For example, the PHY layer attaches to the AP,
> > >
> > >
> > > but the TCP layer
> > >
> > >
> > > attaches to the destination host.
> > >
> > > Mike.
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Stefano M. Faccin
> > > [mailto:stefano.faccin@NOKIA.COM]
> > > Sent: Friday, September 30, 2005 1:08 AM
> > > To: STDS-802-21@listserv.ieee.org
> > > Subject: Re: [802.21] [DNA] Prefix
> > >
> > >
> > > information for link
> > >
> > >
> > > identification in DNA
> > >
> > >
> > > Yoshihiro,
> > > I'm not sure why should restrict the
> > >
> > >
> > > term PoA to have only a
> > >
> > >
> > > L2 meaning as you suggest below. I
> > >
> > >
> > > think we should
> > >
> > >
> > > distinguish clearly between L2 PoA and L3 PoA.
> > > For me, the L3
> > > PoA is where the terminal gets IP conenctivity.
> > > E.g. for GPRS
> > > the L3 PoA is the IP link on which the
> > >
> > >
> > > GGSN is located. In
> > >
> > >
> > > L2, PoA is the point where the access-specific
> > > L2 connection
> > > terminates (e.g. an AP in 802.11).
> > > Stefano
> > >
> > >
> > >
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> > >
> > >
> > >
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> >