Subject: Re: [rrg] Terminology straw poll

From: [email-masked] (Noel Chiappa)
Date: Fri, 11 Jun 2010 19:13:06 -0400 (EDT)

> From: Dae Young KIM <[email-masked]>

    > So, in MAC, a node can be located without extra use of any other
    > numbers.

{Oh, what the heck, it's late Friday afternoon, I'll bite.}

So where is the Ethernet interface with MAC address "00:50:04:53:09:7F"?
(Since you claim it "can be located without .. use of any other numbers".)

	Noel

---

From: Dae Young KIM <[email-masked]>
Date: Sat, 12 Jun 2010 08:23:48 +0900

No, I'm talking in the MAC layer. Be in the L2 network.

In MAC L2 network, there's only one number type, MAC address pointing
to a MAC node.

There's no such thing as MAC interface in MAC L2 network.

On Sat, Jun 12, 2010 at 8:13 AM, Noel Chiappa <[email-masked]> wrote:
>    > From: Dae Young KIM <[email-masked]>
>
>    > So, in MAC, a node can be located without extra use of any other
>    > numbers.
>
> _______________________________________________
> rrg mailing list
> [email-masked]
> http://www.irtf.org/mailman/listinfo/rrg
>

-- 
DY

---

From: Tony Li <[email-masked]>
Date: Fri, 11 Jun 2010 17:52:36 -0700

> There's no such thing as MAC interface in MAC L2 network.

Does the MAC address 'point'?  It seems like a MAC 'address' is nothing more
than a flat, globally unique namespace.

Certainly if I'm on a L2 network and I change my physical attachment, I can
change my location without changing my MAC address.

Yet I can't do that with my postal address.

If we look to the dictionary, we find:

address |əˈdres; ˈaˌdres|
noun
1 the particulars of the place where someone lives or an organization is
situated : they exchanged addresses and agreed to keep in touch.
• the place itself : our officers went to the address.
• Computing a binary number that identifies a particular location in a data
storage system or computer memory.

So it seems like location is necessarily a fundamental component of the
conventional definition of an 'address'.

I humbly suggest that in fact, the MAC address is not, in actuality, an
address at all and is simply an identifier.  Yes, you can forward on it, but
then you can forward on any global flat namespace if you put your mind to
it.  Full human names, anyone?

Regards,
Anthony Joseph Li (Full human name)
Location: ???

---

From: William Herrin <[email-masked]>
Date: Fri, 11 Jun 2010 21:10:40 -0400

> than a flat, globally unique namespace.

Tony,

A MAC address doesn't "point" or DO anything else. It's just a big integer.

A MAC address is USED by at least three distinct functions:

1. By a switch determining which port or ports to repeat a received packet on.
2. By a NIC determining whether a particular packet should be repeated
from the wire to a host's software stack.
3. By a network stack preparing to transmit a particular packet to its next hop.

What identification function do you see happening here? All I see is
forwarding decisions.

Regards,
Bill Herrin

-- 
William D. Herrin ................ [email-masked]  [email-masked]
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

---

From: Tony Li <[email-masked]>
Date: Fri, 11 Jun 2010 18:26:03 -0700

Hi Bill,

> A MAC address doesn't "point" or DO anything else. It's just a big integer.

Exactly my point.  The properties of the namespace include global
uniqueness, but not location (topological, geographic, or otherwise).
 
> What identification function do you see happening here? All I see is

Again, function 1 does not make the namespace topologically sensitive.  It's
just using a flat identifier space and explicitly learning the location of
the identifier.  This is clear if you consider the situation before the host
generates a packet: before the switch learns of the identifier, it has NO
idea where the host is in the network.  And again, you can do this on ANY
flat namespace.  Doesn't make that namespace an address.

Function 2 is filtering based on an identifier.

Function 3 is simply including a source identifier.  It's only real purpose
is to support the learning function for function 1.

Tony

---

From: William Herrin <[email-masked]>
Date: Fri, 11 Jun 2010 21:45:14 -0400

On Fri, Jun 11, 2010 at 9:26 PM, Tony Li <[email-masked]> wrote:
> idea where the host is in the network.

So it defaults to repeating the packet to all ports where a router
would have chosen to drop the packet.

That's the difference between an identifier and a locator? An
identifier defaults to flood while a locator defaults to drop?

> Function 2 is filtering based on an identifier.

Is it now? Last I heard it, different process subscribe to different
multicast MACs and can even subscribe to different unicast MACs (e.g.
a host OS with guest virtual servers). There's a decision about which
process to repeat the packet to. Just like a router, it defaults to
not repeating the packet if the destination MAC matches none of the
known destinations.

> is to support the learning function for function 1.

Actually, I was talking about the destination MAC that gets tacked on
from the ARP table, not the implicit source announcement (much like a
route announcement) that lets the switch know which port to repeat
subsequent packets to.

But hey, you say poTAYto, I say poTAHto and we all dance a little jig.

Regards,
Bill

---

From: Dae Young KIM <[email-masked]>
Date: Sat, 12 Jun 2010 10:51:15 +0900

> Anthony Joseph Li (Full human name)

You ask DY Kim at the entrance to Corea, and theoretically, if it's a
FQNM, they will locate me for you. You don't have to know my postal
address beforehand. Actually, we have social security number, which
has no locational structure. You give the number at entry, and they
will lead you/packets to me.

I mean, as foreigner, you don't have to bother with the internal
locational structure of the address. It's their job, not yours.

In fact, all this thread by me started with my saying effectively that

   - ILNP Locator identifies a subnet. So, it can also be interpreted as ID.
   - So, again with Locator, we have semantic overloading.
   - LISP ID (EID) is routable within a site. So, it can also be
interpred as (intra-site) Locator.
   - So, ID can also be semantically overloaded.
   - So, semantic overloading may not be the real problem with the IP
address. Something else might have been to blame.

-- 
DY

---

From: Tony Li <[email-masked]>
Date: Fri, 11 Jun 2010 19:00:32 -0700

Hi Bill,

> identifier defaults to flood while a locator defaults to drop?

Actually, the router would have forwarded the packet whether or not the
destination is present (up until the L2 mapping fails, at which point its
stuck).  Again, the IP address that the router uses contains location.

You can see this with other addressing schemes:

170 W. Tasman Dr.
San Jose, CA USA

This contains location information, regardless of the individual
(identifier) that you're trying to reach, and:

+1 408 853 XXXX

A phone number includes political and geographic information and specifies a
particular CO in the PSTN, regardless of the least significant bits.

> not repeating the packet if the destination MAC matches none of the

Virtualization changes nothing except that the logical entities are
physically co-located.

Multicast MAC 'addresses' are also just filtering entities: the network
knows nothing about the location of the listeners and simply floods the
packet in the hope that something cares.

As you know, this is even known as MAC address filtering in the hardware.

I'll be the first grant you that an L3 multicast address isn't so much about
topology as a group of listeners and thus is itself not a true 'locator'.
We fudge it with a lot of software.  ;-)

> route announcement) that lets the switch know which port to repeat

Ah sorry, I misinterpreted.

Even then, that's not a true forwarding function, so much as an identifier
translation function.  The host that generates the ARP has some notion of
(L3) location based on the IP address, but learns nothing of the L2 location
of the next hop even as a part of ARP.

> But hey, you say poTAYto, I say poTAHto and we all dance a little jig.

ToMAYto.  ;-)

Happy Friday,
Tony

---

From: [email-masked]
Date: Sat, 12 Jun 2010 04:24:47 -0400

Please, please, please. We shouldn't screw up (by semantic overloading) new terms.

A locator of a node denotes the node's location and in case that node changes its location it has to get a different locator.

A locator of a subnet (what is this anyway ? isn't it rather an identifier ?) denotes the subnet's location and in case that subnet changes its location
it has to get a different locator.

Heiner