Re: [802.21] [DNA] Prefix information for link identification in DNA
I really like where you are going with the definitions. I would still
recommend L3 be referred as PoI (Point-of-Interface), since L3 interfaces is
a common definition (i.e. network interface, interface standardization at
L3, etc...).
That gives you a clear set of differentiated naming convention with clear
demarcation of OSI stack governance (L2, PoA; L3, PoI; L6/7, PoS).
Also, I would not use PoA as Point-of-Access. I prefer Point-of-Attachment
since it is where the MAC peer-to-peer relationship is established; the
first point of attachment to the network. Point-of-Access is still too
imprecise. Access has too many layered meanings. Access to the AP/BS? Access
to the network? Access to services on the network?
Thanks,
Phillip Barber
Huawei
----- Original Message -----
From: "Andrea Francini" <francini@LUCENT.COM>
To: "Yoshihiro Ohba" <yohba@tari.toshiba.com>
Cc: <STDS-802-21@listserv.ieee.org>
Sent: Monday, October 03, 2005 5:02 PM
Subject: Re: [802.21] [DNA] Prefix information for link identification in
DNA
> Hi Yoshihiro,
>
> I agree with you that the notion of adjacency I am using also applies, in
> the
> case of UE1, to UE2 and UE3 (and not only to the AR). However, the PoA
> definition also includes a "network-side" qualifier that does not apply to
> UE2
> and UE3 and still allows (if really needed) to distinguish the AR from UE2
> and
> UE3.
>
> I understand you mostly oppose the notions of "L3 PoA" and "L3 link".
> Let's see
> if we can get rid of them with the following:
>
> 1. We define "link" and "PoA" in strict L2 sense.
>
> 2. We avoid any link-like or PoA-like definition for L3.
>
> 3. We define the "MIH Point of Service (PoS)" as a network-side
> counterpart of
> the UE for the exchange of MIH information, and the "MIH pairing" as the
> relationship that exists between MIH-enabled UE and MIH PoS when they
> exchange
> MIH messages/information.
>
> With the above arrangement:
>
> A UE attaches to a network through a link that terminates at a PoA. (No L2
> qualifiers needed for "link" and "PoA".)
>
> The UE exchanges MIH information with MIH PoS's. Generally, the MIH PoS
> resides
> at an interface on a network node with which the MIH function of the node
> is
> registered for MIH services. An MIH PoS may or may not be co-located with
> a PoA
> on the same (L2) interface.
>
> It can happen that an interface on an MIH-capable node (i.e., a node that
> contains an MIH function instance) does not host an MIH PoS because the
> local
> MIH function is not registered with that interface for MIH support.
> However, an
> MIH PoS may still be found in the same network node at a different
> interface.
>
> The UE may use L2 transport for exchanging MIH information with an MIH PoS
> that
> is co-located with a PoA.
>
> The UE must use L3 transport for exchanging MIH information with an MIH
> PoS that
> is not co-located with a PoA.
>
> Thanks,
>
> Andrea
>
>
> Yoshihiro Ohba wrote:
>>
>> Andrea has a good example of an L3 link that consists of 802.11 link
>> and Ethernet link, so let me discuss based on the example.
>>
>> Obviously there can be multiple UEs attached to the same AP something
>> like:
>>
>> 802.11 link Ethernet link
>> UE1--------------------- AP ------------------- AR
>> / /
>> UE2-------------------+ /
>> /
>> UE3------------------+
>>
>> Do you call UE2 and UE3 "L3 PoAs of UE1" just because they are
>> adjacent nodes for UE1 in terms of L3? I have a problem with calling
>> UE2 and UE3 as PoAs because UE1 is not really attaching to UE2 and
>> UE3. In fact, there is no notion of attaching to a particular node in
>> IP (though there is a notion of attaching to a network in DNA WG), so
>> I think it is hard to have an agreement on bringing the notion of PoA
>> to IP layer which is not defined in the IETF.
>>
>> Please see my further comment below.
>>
>> On Mon, Oct 03, 2005 at 12:50:46PM -0400, Andrea Francini wrote:
>> > Hi Mike,
>> >
>> > I really appreciate your comments. I think they are moving this part of
>> > the
>> > discussion (definitions and their necessity) in a good direction.
>> >
>> > As I wrote in earlier messages, I recognize well that the definitions I
>> > proposed
>> > have plenty of room for improvement. Your comment points out that now
>> > also the
>> > notion of adjacency would need to be explicitly spelled out for a
>> > better common
>> > understanding.
>> >
>> > So this time, instead of generating another controversial definition on
>> > top of
>> > the previos ones, I'll take a step back and try to be more clear with
>> > the
>> > problem I would like to see solved.
>> >
>> > We started with the attempt to converge on a good definition of Point
>> > of Access
>> > (PoA).
>> >
>> > Why do we need such a definition?
>> >
>> > 1. We need a name for the point in the network from which the UE
>> > obtains
>> > connectivity.
>> >
>> > 2. We need a name for the first point in the network with which the UE
>> > can
>> > exchange MIH-related information (for any of the three MIH services).
>> >
>> > Can a single definition of PoA address both needs at the same time? I
>> > don't
>> > think so, because a single definition cannot capture all possible
>> > combinations
>> > (in particular, it cannot provide a good distinction between the cases
>> > where MIH
>> > is immediately available at the AP/BS and where it is only available
>> > deeper
>> > inside the network). This is why I thought that it made sense to have a
>> > general
>> > notion of PoA (the first point in the network from which the UE obtains
>> > a
>> > certain service) and then further qualify it with the appropriate
>> > attributes
>> > (L2, L3, and MIH are the ones that I originally considered relevant in
>> > the
>> > 802.21 context; TCP can be another one).
>> >
>> > Still in general terms, being the PoA the first point in the network
>> > that the UE
>> > can use as a peer for message exchanges related to a certain service,
>> > defining
>> > the entity that exists between UE and PoA with respect to that service
>> > is the
>> > next step. I thought that "link" could be a good term, although I
>> > realize more
>> > and more that "link" has a strong L2 connotation that may not be easy
>> > to relax.
>>
>> > Whatever term we use, it must convey the notion that the UE and the PoA
>> > are next
>> > to each other on it, otherwise the PoA is no longer "the first point in
>> > the
>> > network". I used "adjacent" in the definition of link, with the idea
>> > that the
>> > adjancency is not necessarily physical, but only logical within the
>> > same context
>> > in which the service obtained from the PoA is defined.
>> >
>> > Think for example of a network of routers that is built on top of a
>> > network of
>> > ATM switches. I consider two routers adjacent if they are on IP hop
>> > away from
>> > each other, independently of the number of ATM switches that exist in
>> > the
>> > physical path between them. Similarly in 802.21, two L3 entities are
>> > adjacent if
>> > no other L3 entity exists in between, independently of the number of L2
>> > segments
>> > (or "L2 links") that connect them.
>> >
>> > In a situation like the following:
>> >
>> >
>> > 802.11 link Ethernet link
>> > UE --------------------- AP ------------------- AR
>> >
>> >
>> > how can we capture the fact that the Access Router (AR) is the first L3
>> > entity
>> > in the access network path of the UE?
>> >
>> > With the definitions I proposed, the 802.11 and Ethernet links are L2
>> > links, the
>> > AP includes the L2 PoA for the UE, the AR includes the L3 PoA for the
>> > UE, and an
>> > L3 link exists between the UE and the AR (of course only after the UE
>> > has
>> > obtained its IP address).
>> >
>> > If the 802.11 interface on the AP is MIH-capable, the AP also includes
>> > the MIH
>> > PoA for the UE, independently of the MIH capabilities of the AR. If
>> > only the
>> > Ethernet interface on the AR is MIH-capable, the AR includes the MIH
>> > PoA.
>>
>> >
>> > With the definitions I proposed, every entity of the example gets an
>> > unambiguous
>> > name. I don't have any problem with changing the names or the wording
>> > of the
>> > definitions, but I still want to have a name for each of the entities.
>> > Any other
>> > proposal should pass the same test.
>>
>> I think that unambiguous naming is also possible even if we call the
>> immediate L2 link to UE as "link", and the end point of the immediate
>> L2 link as "PoA", for example:
>>
>> If the 802.11 interface on the AP is MIH-capable, we can call the AP
>> the MIH PoA (or MIH AP) for the UE, independently of the MIH
>> capabilities of the
>> AR. If only the Ethernet interface on the AR is MIH-capable, we can
>> call the AR the MIH AR.
>>
>> On the other hand, regardless of which direction we take (i.e.,
>> defining link and PoA for each layer vs. defining link and PoA for L2
>> only), definition of the "immediate L2 link for the UE" still depends
>> on each media, e.g., a PDP context can be the immediate L2 link for
>> GPRS, and an association between a STA and an AP can be the immediate
>> L2 link in 802.11, etc. I think this is more important thing to
>> consider.
>>
>> >
>> > With respect to your specific concerns:
>> >
>> > > I think the link between two adjacent layer 3 entities is actually a
>> > > layer 2 link. To me, the > purpose of any link at layer N is to
>> > > provide a PDU transfer service to layer N+1.
>> >
>> > Do you mean that two layer-3 entities are adjacent only if they are
>> > connected by
>> > a single L2 link, i.e., only if no other L2 node exists between the
>> > respective
>> > L2 interfaces? What term could then be applied to the two L2 interfaces
>> > to
>> > express the fact that no other L2 node exists between them?
>> >
>> > In the IP-over-ATM example, two neighboring routers can be attached to
>> > ATM nodes
>> > that are connected by a single ATM VC or by a chain of ATM VC's. With
>> > my
>> > definition of adjacency, the two routers are adjacent in both cases
>> > (i.e.,
>> > neighboring = L3-adjacent). Would it be the same with your definition?
>> >
>> > I'm not trying to say that they should necessarily be called adjacent,
>> > but to
>> > understand how your definition would apply to the example.
>> >
>> > > If you took your definitions as they are, then the layer 3 link
>> > > coming up would not allow TCP > or UDP to flow - you'd still have to
>> > > wait for IP address assignment - and that sounds wrong to > me.
>> >
>> > I think it should be implicit to have IP addresses in place before an
>> > L3 link
>> > can exist. If the implication is not clear, an explicit statement can
>> > be easily
>> > added.
>>
>> For IP, just having an IP address is not sufficient to claim that
>> there is L3 connectivity between an UE and an IP node on the same IP
>> link. In IPv6 Neighbor Discovery protocol (RFC 2461), at least there
>> must be a neighbor cache entry for the communicating node with
>> "REACHABLE" state to *roughly* claim that the node is reachable
>> (within ten seconds ago).
>>
>> Regards,
>>
>> Yoshihiro Ohba
>>
>> >
>> > Thanks,
>> >
>> > Andrea
>> >
>> >
>> > Mike Moreton wrote:
>> > >
>> > > Andrea,
>> > >
>> > > I really like these definitions - I think they are clear and precise,
>> > > which gives a good basis to argue from.
>> > >
>> > > Which is what I'm going to do!
>> > >
>> > > I think the link between two adjacent layer 3 entities is actually a
>> > > layer 2 link. To me, the purpose of any link at layer N is to
>> > > provide a PDU transfer service to layer N+1.
>> > >
>> > > If you took your definitions as they are, then the layer 3 link
>> > > coming up would not allow TCP or UDP to flow - you'd still have to
>> > > wait for IP address assignment - and that sounds wrong to me.
>> > >
>> > > Mike.
>> > >
>> > > > -----Original Message-----
>> > > > From: Andrea Francini [mailto:francini@LUCENT.COM]
>> > > > Sent: Friday, September 30, 2005 8:41 PM
>> > > > To: STDS-802-21@listserv.ieee.org
>> > > > Subject: 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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