Subject: [mif] about draft-hong-mif-analysis-scenario-00

From: marcelo bagnulo braun <[email-masked]>
Date: Sun, 15 Mar 2009 21:15:21 +0100

Hi,

i found this document to be very confusing
I am not sure, but it seems to me to be more an analysis of how a 
particular approach, namely, the connection manager, interacts with the 
different layers, rather than a scenario analysis, whcih si what i was 
expecting (but as i said, i haven't been able to understnad it very 
well, so i may be very well mistaken)

some questions below...

2.1. Relation between network interface and destination address

   The host may change its interface for communication with a
   correspondent node due to movement or change of network environments.
   Before the change of network interface, when the host uses (I1, IP1)
   and sends packets to a correspondent node, the source address and
   destination address of packets is (IP1, IP3) and the used network
   interface is I1.  If the host moves other network N2, and then the
   host uses (I2, IP2) and the used network interface is I2.  Before the
   change of network interface, the destination address (IP3) of the
   correspondent node is mapped to a network interface I1.  However
   after the change of network interface, when an application tries to
   send packets to the correspondent node, it continually tries to use a
   network interface I1 if the relation of destination address IP3 and
   network interface I1 is not properly updated.  If this situation
   happens, even though, the network interface is changed to I2, packets
   are delivered to I1 at the link layer or L2 layer.  The communication
   sessions will be disrupted.

I am not sure i understand the problem here.
Are you considering the case of an ongoing communication e.g. an 
established TCP connection that the node wants to preserve from I1 to I2?
Or are you talking about two different TCP connections, one estbalished 
using I1 and then the host moves and wants to establish a new 
connection, but now using I2?

I am asking cause i think the first problem is a mobility problem and 
out of the scope for MIF (if you want to do that, you should use MIP)
In the second case, i don't see any problems here. I mean, when the new 
TCP connection is estbalished a new socket is used and if I1 is down, 
the host should naturally use I2, so i fail to see the problem

2.2. Considerations for heterogeneous environments with different IP

      version

   If a host moves between networks with a single network interface or
   access technology, the change may be only a network address.  Because
   the host has an access technology of the single network interface, it
   doesn't need to consider other aspects such as the change of access
   technology and IP version.

i am not sure if i follow.... my laptop can connect to a wifi with IPv4 
and with IPv6, so why having a single interface doesn't pose a problem 
with the IP version?

   If a host moves between networks with multiple network interfaces or
   access technologies, other changes may happen.  If a host has
   multiple network interfaces (one is a WLAN interface and the other is
   a CDMA interface) in heterogeneous environments, changes include the
   network address, network interface and access technologies of the
   selected network interface after moving.  Particularly, the main
   issue is the network address.  Currently in Korea, we can use IPv6
   based WLAN service but it is impossible to use IPv6 based CDMA
   service.  The deployment of IPv6 based CDMA service will be done
   sooner or later.  Until the deployment of IPv6 based CDMA service, if
   we want to use IPv6 service with a CDMA network interface, we must
   consider how to use IPv6 service in IPv4 based CDMA network.

I think you should be more explicit about what are the problems you are 
trying to point out. What are the specific problems that a node 
experiences when moving to a network with a different IP version?

3. Scenarios of host with multiple interfaces

are you describing scenarios or approaches to deal with multiple interfaces?

3.1. Multiple interfaces but none layer do not support

The title of this section is really non intuitive.

   At the beginning time, a host adapts multiple interfaces but other
   layers do not support multiple interfaces.

I don't understand what do you mean by this

   Because the overhead
   and cost of modification of original network layer, transport layer,
   and application layer, it is difficult to modify other layer all at
   once to support multiple interfaces in a host.

Why do you need to modify the transport layer to support multiple 
interfaces?

   In this case, the connection manager
   must provide method to use multiple interfaces even though other
   layers do not support multiple interfaces.

This seems a solution to me. Are you describing different solutions to 
the problem?

3.2. Multiple interfaces and only network layer support

   As time goes on, a host adapts multiple interfaces and network layer
   support multiple interfaces. (transport layer, application layer, and
   user are not aware of the existence of multiple interfaces.)  The
   Mobile IPv6 which is extended to support multiple interfaces could be
   in this case [7].

what do you need MIP for?

   In this case, the connection manager must provide
   method to use multiple interfaces with the help of the network layer.

I am not sure what does the connection manager is...

3.3. Multiple interfaces and network layer and transport layer support

   In this case, a host adapts multiple interfaces and network layer and
   transport layer support multiple interfaces. (application layer, and
   user are not aware of the existence of multiple interfaces.)  Until
   now, it seems that existing TCP/UDP could not have the capability to
   support multiple interfaces.  And it seems that SCTP could have the
   capability to support multiple interfaces but it needs to be more
   enhanced.

what enhancement is needed for sctp?
Why would TCP or UDP need to be aware of the multiple interfaces?

  In this case, the connection manager must provide the
   method to use multiple interfaces with the help of the network layer
   and the transport layer.

---

From: "Yong-Geun Hong" <[email-masked]>
Date: Mon, 16 Mar 2009 21:14:52 +0900

Hi, Marcelo.

Thanks for your comments.

See inline reply.

> connection, but now using I2?

 I am considering the case of an ongoing communication.

> the host should naturally use I2, so i fail to see the problem

  It is not related to a mobility problem. It is caused by the changing of
 relation between network interface and destination address. In RFC 1122,
route
 cache includes Local IP address, Destination IP address, Type(s)-of-
Service,
 Next-hop gateway IP address. Typically, in Linux OS, additional fields
(such as
 Interface and use) are included. So the proper updating route cache is a
 different to a mobility problem.

> and with IPv6, so why having a single interface doesn't pose a problem

 Having a single interface can pose problem with the IP version.
 Actually, I am not sure how many times this situation happens.

> experiences when moving to a network with a different IP version?

 As described in above, let's assume that WLAN access network provides only 
 IPv6 service and CDMA access network provides only IPv4 service. If a host
starts
 communication in WLAN access network and establishes IPv6 connection with
a correspondent
 node. And then the host changes network interface to CDMA interface. The
problem is how to 
 maintain the IPv6 connection in IPv4 CDMA access network. 

> are you describing scenarios or approaches to deal with multiple

 My intention is describing of scenarios of multiple interfaces in a host.

> I don't understand what do you mean by this

 A few years ago, we implemented a host with multiple interfaces without
changing of 
 network layer, transport layer, and application layer. 

> Why do you need to modify the transport layer to support multiple

 Multiple interfaces can provide simultaneous connections. The simultaneous
connections
 will be more enhanced with the help of transport layer. 

> This seems a solution to me. Are you describing different solutions to

 Yes, it can be a solution. We will think over it. 

> what do you need MIP for?
 
 My intention is that Mobile IPv6 is extended to support multiple
interfaces (multiple CoAs).
 So, other module in network layers can be enhanced to support multiple
interfaces.
 I don't say MIP is need. 

> what enhancement is needed for sctp?

 I know that basic SCTP supports only one active connection. (one is
primary and the other is secondary for backup, etc.)
 To support multiple connections in transport layer with SCTP, there are on-
going works. 

 Best regards.

 Yong-Geun.

> _______________________________________________
> mif mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/mif

---

From: marcelo bagnulo braun <[email-masked]>
Date: Mon, 16 Mar 2009 18:21:07 +0100

>  I am considering the case of an ongoing communication.

so the problem you are considering is when an ongoing TCP connection
moves from one interface to a differnet one?
This certainly looks to me as a clear mobility problem...
>  different to a mobility problem.

So, are you assuming that all the interfaces have the same IP address
configured?
Or are you assuming a weak host model, where an IP address configured to
a given interface can be used as a source address for packet sent
through a different interface?
>  Having a single interface can pose problem with the IP version.

which ones?
>  Actually, I am not sure how many times this situation happens.

i guess that my point is that i fail to see why this is related to
having multiple interfaces

>  maintain the IPv6 connection in IPv4 CDMA access network. 

This is a mobility problem or a multihoming problem if you like but imho
clearly out of the scope of this work

>  will be more enhanced with the help of transport layer. 

while this is true, imho is out of the scope of this work

> interfaces (multiple CoAs).

this is already done. see the mcoa draft in the mext wg
> haven't followed sctp closely, but in any case it seems out of the scope for this work

Regards, marcelo

---

From: Lars Eggert <[email-masked]>
Date: Tue, 17 Mar 2009 11:32:11 -0700

> This certainly looks to me as a clear mobility problem...

To me, too. I thought this was out of scope.

Lars

---

From: <[email-masked]>
Date: Wed, 18 Mar 2009 14:21:20 +0100

Hi all,

I'm confused too. I think there is a consensus that mobility is out of the scope of MIF. However it seems to me that this draft describes inter-access mobility problem and "mobile IP" issues.

>From my understanding, in the context of MIF, the interest of a virtual interface is that it could make the application agnostic about the source address selection function. So, an application uses a virtual source address and the MIF's decision function maps to a physical address. But maybe I 'm missing something.... comments are welcome.

Regards,
Pierrick 

> -----Message d'origine-----
> De : [email-masked] [mailto:[email-masked]] De la part de Lars
> Eggert
> Envoyé : mardi 17 mars 2009 19:32
> À : marcelo bagnulo braun
> Cc : 'mif'
> Objet : Re: [mif] about draft-hong-mif-analysis-scenario-00
>

---

From: "Yong-Geun Hong" <[email-masked]>
Date: Thu, 19 Mar 2009 10:46:58 +0900

Hi, all

See inline reply.

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf Of
> [email-masked]
> Sent: Wednesday, March 18, 2009 10:21 PM
> To: [email-masked]; [email-masked]
> Cc: [email-masked]
> Subject: Re: [mif] about draft-hong-mif-analysis-scenario-00
> 
> 
> Hi all,
> 
> I'm confused too. I think there is a consensus that mobility is out of the
> scope of MIF. However it seems to me that this draft describes inter-
> access mobility problem and "mobile IP" issues.
> 

 I agree that mobility issues (especially which is related to Mobile IP/NEMO, etc)
 is out of scope of MIF. In current MIF charter, there is "Problem statement" - 
 A document describing the problems caused by the multiple interfaces in the host
(Informational). 

 Regarding the change of relation between network interface and destination address,
 this problem is caused by not only TCP connection but also UDP connection. TCP/UDP 
 communication with previous interface affects the routing information in the MIF host.
 If the MIF host choose another interface and the relation between interface and destination
 address is not properly updated, TCP/UDP communication with newly chosen interface may have
 problem.

 And the change of network interface during TCP/UDP communication can be happened by various
 reasons. The movement of a MIF host is one of them. Without moving, due to the change of policy,
 the change of network environment, and the change of user preference, the interface can be changed.

 Do all of these reasons belong to mobility issues?

 Best regards.

 Yong-Geun.

> From my understanding, in the context of MIF, the interest of a virtual
> interface is that it could make the application agnostic about the source
> address selection function. So, an application uses a virtual source
> address and the MIF's decision function maps to a physical address. But
> maybe I 'm missing something.... comments are welcome.
> 
> Regards,
> Pierrick
>

---

From: marcelo bagnulo braun <[email-masked]>
Date: Thu, 19 Mar 2009 10:25:51 +0100

> >From my understanding, in the context of MIF, the interest of a virtual interface is that it could make the application agnostic about the source address selection function. So, an application use…

what do you mean by a virtual interface?
You mean an IP address that is not associated to any physical interface?
If that is the case, this can work, as long as the the multiple 
interfaces are connected tot he same ISP and that the ISP has its 
routing arranged in such a way that both interfaces can be reached 
through the same IP address, which i guess really depends on the ISP config.

Regards, marcelo

---

From: marcelo bagnulo braun <[email-masked]>
Date: Thu, 19 Mar 2009 10:31:59 +0100

Yong-Geun Hong escribió:
>  this problem is caused by not only TCP connection but also UDP connection. 
right, but this has two very different cases. One case is when the same 
IP address or the original interface can be used in the second 
interface. This seems a very specific case, where multiple interfaces 
are connected tot he same ISP and the ISP is able to reach the different 
interfaces with the same IP address (which doesn't seems trivial to me)

the other case is where different interfaces need to use different IP 
addresses. If this is the case, this is a mobility problem which can 
should be solved using MIP.

> TCP/UDP 
right, so are you suggesting we make sure that it keeps on using the 
original interface? or are you suggesting we support the usage of 
multiple interfaces in the same connection?

>  Do all of these reasons belong to mobility issues?

no, depending on which of the cases that i described above are you 
talking about, the reasonable solution can be simply MIP.
I mean, if you need to change the address involved in a communication, 
you should go for MIP, i guess.

Regards, marcelo

>>> De : [email-masked] [mailto:[email-masked]] De la part de
>>>       
>> Lars
>>     
>>> Eggert

---

From: <[email-masked]>
Date: Thu, 19 Mar 2009 10:32:35 +0100

Hi Marcello,

> De : marcelo bagnulo braun [mailto:[email-masked]]
> Envoyé : jeudi 19 mars 2009 10:26
> À : SEITE Pierrick RD-RESA-REN
> Cc : [email-masked]; [email-masked]
> > I'm confused too. I think there is a consensus that mobility is out of
> the scope of MIF. However it seems to me that this draft describes inter-

Yes

> through the same IP address, which i guess really depends on the ISP

Good point...

---

From: "Yong-Geun Hong" <[email-masked]>
Date: Sat, 21 Mar 2009 14:55:23 +0900

Hi, Marcelo.

Please see inline reply.

> From: marcelo bagnulo braun [mailto:[email-masked]]
> Sent: Thursday, March 19, 2009 6:32 PM
> To: Yong-Geun Hong
> Cc: [email-masked]; [email-masked]; [email-masked]
> the

 Yes, you are right. 

> multiple interfaces in the same connection?

 I think that it is difficult to keep on using the original interface even though
 the used interface is changed. I hope we develop the method for the usage of multiple
 interfaces in the same connection, because I understand that the main motivation of MIF
 is simultaneously using multiple interfaces in a host. For this, the problem of the change
 of IP address of different interfaces may be solved using MIP and other problems like 
 invalid route cache should be also solved by other ways. 

> you should go for MIP, i guess.

 I understand your point.

 Thanks for your valuable comments.

 Best regards.

 Yong-Geun.

---

From: marcelo bagnulo braun <[email-masked]>
Date: Sat, 21 Mar 2009 15:27:06 +0100

Yong-Geun Hong escribió:
>
>>> TCP/UDP
>>>  communication with previous interface affects the routing information
>>>       
>> in the MIF host.
>>     
>>>  If the MIF host choose another interface and the relation between
>>>       
>> interface and destination
>>     
>>>  address is not properly updated, TCP/UDP communication with newly
>>>       
>> chosen interface may have
>>     
>>>  problem.
>>>
>>>
>>>       
>  interfaces in the same connection,

that's kind of strange. I mean, using multiple interfaces 
simoultaneously for a single connection?
I mean, afaik, the two common cases considered are: use interfaces 
sequentially for the same connection (useful to preserve ongoing 
communications when one access becomes unavailble) or use multiple 
interfaces simoultaneoulsy for different connections (i.e. my web 
browsing over one interface and my sip traffic over a different one)

using multiple interfaces simultaneously for the same connection seems 
odd to me... do you have a particular use case in mind?
>  because I understand that the main motivation of MIF
>  is simultaneously using multiple interfaces in a host. 
sure, but for different connections/flows, i understand

> For this, the problem of the change
>  of IP address of different interfaces may be solved using MIP

imho you are mixing the two cases i describe above.
You can use MIP to preserve an established connection when you change 
interface and you could also use MIP flow binding for selecting which 
connection goes over which CoA,

regards, marcelo

>  and other problems like 
>>>  And the change of network interface during TCP/UDP communication can be
>>>       
>> happened by various
>>     
>>>  reasons. The movement of a MIF host is one of them. Without moving, due
>>>       
>> to the change of policy,
>>     
>>>  the change of network environment, and the change of user preference,
>>>       
>> the interface can be changed.
>>     
>>>> interface is that it could make the application agnostic about the
>>>>         
>> source
>>

---

From: "Joel M. Halpern" <[email-masked]>
Date: Sun, 22 Mar 2009 12:07:04 -0400

Actually, the transport folks are looking at a number of ways of 
allowing Transport (TCP is the focus, but it applies to others) to use 
multiple src-dest aqddress pairs for TCP communication.  This can give 
better throughput and better failure recovery.
But it is very much a Transport area activity, with some relationship to 
research in the Routing space.
It should not be a MIF work item.

Yours,
Joel

marcelo bagnulo braun wrote:
...
> sure, but for different connections/flows, i understand
...

---

From: marcelo bagnulo braun <[email-masked]>
Date: Sun, 22 Mar 2009 17:11:55 +0100

Right, but i guess you need something on both ends to support multiple 
addresses in the same tcp connection (such as MIP or multipath TCP) to 
make this work. So, this is why i am not sure how this would fit in mif.

Joel M. Halpern escribió:
> But it is very much a Transport area activity, with some relationship 
> to research in the Routing space.
>> using multiple interfaces simultaneously for the same connection 
>> seems odd to me... do you have a particular use case in mind?