Subject: Re: [DNA] Last call: Detection of Network Attachment (DNA) in IPv4 (fwd)

From: JinHyeock Choi <[email-masked]>
Date: Wed, 25 May 2005 14:07:55 +0900

Dear Bernard

I'd like to mention a few differences between DNA for IPv4 (DNAv4) 
and DNA for IPv6 (DNAv6). 

1. Abbreviation
For IPv4, DNA stands for "Detection of Network Attachment", whereas 
for IPv6, DNA stands for "Detecting Network Attachment". 

2. DNA Goal
I understand DNAv4 aims to detects movement (or lack of movement) 
between subnets, and obtains (or continue to use) a valid IPv4 configuration. 

DNAv6 aims to detect movement (or lack of movement) between links 
to ascertain the validity of existing IP configuration but does not include 
the actual IP configuration procedure.  

3. Point of Attachment
In DNA mailing list, we define a term "Attachment Point", which represents 
the link-layer connection. 

For example, assume the case of two 802.11 b APs and a router on the same 
ethernet link. Each AP is an Attachment Point and if a host moves from 
one AP to another, it has moved to a different Attachment Point. 
     
It's my impression that the "Attachment Point" from DNA WG and 
"Point of Attachment" from the draft doesn't mean the same thing. 
 
Also I am glad & relieved to see that the draft no longer includes the term 
'link identifier'. Though the draft still uses the term 'link' a few times, 
the meaning is clear from the context. 

Thanks for your kind consideration.   

Best Regards

JinHyeock

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From: Bernard Aboba <[email-masked]>
Date: Tue, 24 May 2005 23:22:49 -0700 (PDT)

Thank you very much for your review.

> for IPv6, DNA stands for "Detecting Network Attachment".

We can change the title.

> the actual IP configuration procedure.

I think DNAv4 also ascertains the validity of an existing IP
configuration.  If it is valid, then the host continues to use it.  But if
it is not valid then the host needs to obtain a new configuration using
mechanisms outside of DNAv4 (e.g. DHCP).  Is this different than DNAv6?

> "Point of Attachment" from the draft doesn't mean the same thing.

In the case above, I think that the AP would also be called a "Point of
Attachment", so they seem very similar.   I can change the document to say
"Attachment Point" instead.

> the meaning is clear from the context.

I did get questions about the meaning of terms such as "link", "Link Up",
"Link Down" etc.  Perhaps I should post all the terminology that is used
so that we can make sure we are consistent between DNAv4 and DNAv6.

---

From: JinHyeock Choi <[email-masked]>
Date: Wed, 25 May 2005 16:02:45 +0900

Bernard 

> > for IPv6, DNA stands for "Detecting Network Attachment".

ok. Thanks for your trouble. 
 
> mechanisms outside of DNAv4 (e.g. DHCP).  Is this different than DNAv6?

The difference I had in mind is whether DNA includes IP configuration or not. 
In DNAv6, Goals draft says:

                             DNA process does not include the actual
   IP configuration procedure.  For example, with respect to DHCP, the
   DNA process may determine that the host needs to get some
   configuration information from a DHCP server.  However, the process
   of actually retrieving the information from a DHCP server falls
   beyond the scope of DNA.

Whereas, I assumed that DNAv4 process includes actual IP configuration 
process because of "2.3.  IPv4 Address Acquisition". If not, I see 
little difference. 
 
> "Attachment Point" instead.

I might be mistaken. In the above example, I thought a router is the 
"Point of Attachment" because of the definition below.  

Point of Attachment
     A location within the network where a host may be connected.  This
     attachment point can be characterized by its address prefix and
                                                             
^^^^^^^^^^^^^^^^^^^^^^^^^^^
     next hop routing information.
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

If not, I see little difference and no need to change term. But it may 
be of help to present an example of "Point of Attachment".
  
> so that we can make sure we are consistent between DNAv4 and DNAv6.

That would be of help. While writing Goals draft for DNAv6, we had much 
trouble from the ambiguity around the term "link". I still worry the issue will 
come back again, so would be glad, if we set this straight.  

Best Regards

JinHyeock

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From: Brett Pentland <[email-masked]>
Date: Wed, 25 May 2005 17:23:18 +1000

>      attachment point can be characterized by its address prefix and

Yes, when I read this definition, I took it to mean the same as the term
"link" (using the definition of link in 2460).  Thus if two 802.11b APs
were connected through an Ethernet hub to a router, then regardless of
which AP a host associates with, it connects to the same "Point of
Attachment".  This is distinct from "Attachment Point" as we've
discussed it on this list (as JinHyeock points out) where each AP would
represent a separate "Attachment Point".

Brett.

---

From: "Soohong Daniel [email-masked]" <[email-masked]>
Date: Wed, 25 May 2005 16:55:33 +0900

>mechanisms outside of DNAv4 (e.g. DHCP).  Is this different than DNAv6?

In my understanding, the origin of DNAv4 is quitely different 
from DNAv6 since it is basically based on DHCPv4 for obtaining 
its own IP address (LLA is used for DNAv4 of course). DNAv4 host 
must initiate its address configuration procedure with DHCPDISCOVER 
message. DNAv6 does may not consider DHCPv6 environment but totally
RS/RA operation. In conclusion, the different DNA Goal seems appropriate.
I am not sure why we need to harmonized between DNAv4 Goal and 
DNAv6 Goal. 

Thanks.

---------------------------------------------
Daniel (Soohong Daniel Park)
Mobile Platform Laboratory, SAMSUNG Electronics.

---

From: Bernard Aboba <[email-masked]>
Date: Wed, 25 May 2005 05:01:22 -0700 (PDT)

> process because of "2.3.  IPv4 Address Acquisition". If not, I see

The DNAv4 draft does determine when the host needs to get some
configuration information from a DHCP server.  The process for that is
governed by the DHCPv4 specification, though the DNAv4 spec does describe
the state that the DHCPv4 client should be in (INIT-REBOOT, etc.).

>      attachment point can be characterized by its address prefix and

Ah.  This definition is perhaps misleading. Is there a definition for
"Attachment Point" that we could substitute for it?

> be of help to present an example of "Point of Attachment".

We will change the text to refer only to "Attachment Point".

> come back again, so would be glad, if we set this straight.

Great.  We will new definitions for "Attachment Point", "Link Up" and
"Link Down" and will then post all the terminology to the list.

---

From: Bernard Aboba <[email-masked]>
Date: Wed, 25 May 2005 05:05:17 -0700 (PDT)

> represent a separate "Attachment Point".

In reviewing the document, I think that the term "Most Likely Point of
Attachment" really means "Most Likely Network", where as when the document
refers to changing the "point of attachment" it really means changing the
"attachment point".

I will try to clean up the document to make it clear what is being
discussed.

---

From: JinHyeock Choi <[email-masked]>
Date: Thu, 26 May 2005 10:28:53 +0900

> the state that the DHCPv4 client should be in (INIT-REBOOT, etc.).

ok. Then I see no difference between DNAv4 & DNA v6 w.r.t. this.  

> We will change the text to refer only to "Attachment Point".

I come to think that we would better use "Point of Attachment" 
because we can't use abbreviation for "Attachment Point" and 
IEEE 802.21 WG is using "PoA" already. 

> refers to changing the "point of attachment" it really means changing the

I agree. I think the term "Most Likely Point of Attachment" 
is confusing.     

Best Regards

JinHyeock

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From: Bernard Aboba <[email-masked]>
Date: Wed, 25 May 2005 22:17:46 -0700 (PDT)

> IEEE 802.21 WG is using "PoA" already.

OK.  I will use "Point of Attachment" instead.