Subject: [manet] Technical issue 3: default route (Route.pfxlen)

From: "Susan Hares" <[email-masked]>
Date: Mon, 14 Jan 2013 00:39:31 -0500

My question:  What use cases led to ADOV2 not having a default route
included?   0/0 

Reasons for: 

1)  Manet mobile area network to internet access can insert 0/0 default to
direct all traffic. 

The connection of a mobile network can occur from a single point or multiple
points. Mobile networks could allow many possible connections to the fixed
network e.g. 10), but only have 1-2 active at a time.  Did the use cases
suggest this scenario? 

2)  A fixed node detecting a MANET network could easily insert default
quickly to quickly set-up Internet connectivity   

Reason against: 

1)  Default-free-zones will set-up conflicting defaults within the ADOV2
region. Pro-active algorithms with multiple default can be difficult to
design (see multi-homing discussions in IPv6, BGP, 802.11s mesh networks).  

2)  Extra traffic may be caused as defaults balance between n exit points.  

3)  Networks would rather have large blocks (e.g. /4 or /8 in v4 or /24 in
IPv6) that allow   

Questions: 

1.  What use cases did you study to examine the default routing in MANET
networks?

2.  Did the WG agree that 0/0 is not a useful prefix?  What was the reason? 

3.  What impact did MANET routing or forwarding policy issues have on this
decision?  

4.  Did someone study the amount of bandwidth consumed to converge to a set
of default routes?  

Exit1                    Exit 2                    Exit 3

|                         |                          |

|                         |                          |

==========================================================

|              MANET network 

      Node 1 node 2      node 3            node 4 node 5

=========================================================

By converge I mean that Exit1, Exit2, and Exi3 are manet routers with
connections to the fixed network. Exit1, Exit2, and exit 3 all want to send
the default route into the manet network. 

What is the result that routing should bring? 

In other multi-homed cases without additional policy, the following would
occur: 

1.  The traffic from node 1 and node 2 is closest to exit 1, and should be
routed to exit 1.  

2.  The traffic from node 3 is closest to exit 2.  Traffic from node 3
should be routed via MANET routing to exit 2.  Similarly, node 4 and node 5
are close to exit 3.  Traffic from node 4 and 5 should be routed to exit 3. 

The real issues is the amount of bandwidth and time it takes to converge to
multiple default exit points in a reactive protocol. 

You may get one and then optimize to another one. In multi-homing, IMHO it
is best to start out with "why" based on real use cases, and then go through
a careful look at topology changes. 

Did you do this? Is there a paper on this work I should read? 

5.  Was this a group decision or were there a few opinions? 

a.   If there were opinions were the differing opinions based on use cases
or deployment scenarios or were there a few opinions?  

b.  If there were opinions were the differing opinions based on use cases or
deployment scenarios? 

Thank you for any help on default route.  In your reply, please be aware
that I'm the co-chair of the IDR (BGP) working group. 

Sue

---

From: Henning Rogge <[email-masked]>
Date: Mon, 14 Jan 2013 08:45:23 +0100

On 01/14/2013 06:39 AM, Susan Hares wrote:
> *Questions: *
>
> 1.What use cases did you study to examine the default routing in MANET
> networks?

I think having multiple default gateways (towards your backbone) is a 
common use case. Both for high volume/data networks and for low powered 
networks down to sensor networks (RPL for example supports multiple 
internet gateways I think).

> 2.Did the WG agree that 0/0 is not a useful prefix?  What was the reason?

I do NOT think we agreed that 0/0 is NOT a useful prefix.

> 3.What impact did MANET routing or forwarding policy issues have on this
> decision?

The main problem with prefixes in reactive routing protocols is that 
they can prevent the trigger of a "no route available" event, which in 
turn triggers the route discovery.

There are administrative solutions to this problem, but its more 
difficult to solve for reactive protocols than proactive ones.

I see two good options to work on this for AODVv2:

a) we say that "announcing prefixes" is out of scope for AODVv2 and that 
it will be addressed in an extension document. I think LOADng is going 
this way too.

b) we add a solution to AODVv2 that allows us to announce prefixes (with 
certain restrictions like administrative black holes)

> 4.Did someone study the amount of bandwidth consumed to converge to a
> set of default routes?
>
> Exit1                    Exit 2                    Exit 3
>
> |                         |                          |
>
> |                         |                          |
>
> connections to the fixed network. Exit1, Exit2, and exit 3 all want to
> send the default route into the manet network.
>
> In other multi-homed cases without additional policy, the following
> would occur:
>
> 1.The traffic from node 1 and node 2 is closest to exit 1, and should be
> routed to exit 1.
>
> 2.The traffic from node 3 is closest to exit 2.  Traffic from node 3
> should be routed via MANET routing to exit 2.  Similarly, node 4 and
> node 5 are close to exit 3.  Traffic from node 4 and 5 should be routed
> to exit 3.
>
> The real issues is the amount of bandwidth and time it takes to converge
> to multiple default exit points in a reactive protocol.
>
> You may get one and then optimize to another one. In multi-homing, IMHO
> it is best to start out with “why” based on real use cases, and then go
> through a careful look at topology changes.
>

Typically routing protocols just dump the traffic into the "closest" or 
"currently known" outgoing gateway. If you need load-balancing, fairness 
or need to care for certain restrictions of gateways, you need 
additional information and protocol parts

(we have implemented an extension like this in the OLSR.org codebase for 
OLSRv1 and a few people are still improving it)

>       5.Was this a group decisionor were there a few opinions?
>
>
>       a. If there were opinions were the differing opinions based on use
>       cases or deployment scenarios or were there a few opinions?
>
>
>       b.If there were opinions were the differing opinions based on use
>       cases or deployment scenarios?
>
> that I’m the co-chair of the IDR (BGP) working group.

I don't think the 0/0 route should be that special... there are other 
kinds of prefixes that might be relevant for AODVv2 too, for example /64 
prefixes in IPv6 networks to allow each AODVv2 node to announce a 
complete subnet attached to the mesh node.

Henning Rogge
-- 
Diplom-Informatiker Henning Rogge , Fraunhofer-Institut für
Kommunikation, Informationsverarbeitung und Ergonomie FKIE
Kommunikationssysteme (KOM)
Fraunhofer Straße 20, 53343 Wachtberg, Germany
Telefon +49 228 9435-961,   Fax +49 228 9435 685
mailto:[email-masked] http://www.fkie.fraunhofer.de

---

From: "Susan Hares" <[email-masked]>
Date: Mon, 14 Jan 2013 09:34:22 -0500

Henning:

Implementing insertion of external routes (any prefix) is a well-known case
from ISIS, OSPF, or OLSR. 

Load balancing in a reactive protocols needs metric passed to measure the
distance to the gateway.  I agree that you can do this in a reactive
protocol, but the design needs to be carefully done.  What I think you are
saying, is that this part is being handed off to a reactive protocol
addition at this point.  

Did I understand correctly?  

I do agree that practically, people do want to insert external routes.  I
would love to see the scenarios for the reactive protocol addition to LOADng
or AODV2.   Did I miss this discussion in the mail list archives? 

Thank you, 

Sue 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Henning Rogge
Sent: Monday, January 14, 2013 2:45 AM
To: [email-masked]
Subject: Re: [manet] Technical issue 3: default route (Route.pfxlen)

> 1.What use cases did you study to examine the default routing in MANET 

I think having multiple default gateways (towards your backbone) is a common
use case. Both for high volume/data networks and for low powered networks
down to sensor networks (RPL for example supports multiple internet gateways
I think).

> 3.What impact did MANET routing or forwarding policy issues have on 
> this decision?

The main problem with prefixes in reactive routing protocols is that they
can prevent the trigger of a "no route available" event, which in turn
triggers the route discovery.

There are administrative solutions to this problem, but its more difficult
to solve for reactive protocols than proactive ones.

a) we say that "announcing prefixes" is out of scope for AODVv2 and that it
will be addressed in an extension document. I think LOADng is going this way
too.

> 1.The traffic from node 1 and node 2 is closest to exit 1, and should 
> be routed to exit 1.
>
> node 5 are close to exit 3.  Traffic from node 4 and 5 should be 
> routed to exit 3.
>
> The real issues is the amount of bandwidth and time it takes to 
> converge to multiple default exit points in a reactive protocol.
>
> You may get one and then optimize to another one. In multi-homing, 
> IMHO it is best to start out with “why” based on real use cases, and 
> then go through a careful look at topology changes.
>

Typically routing protocols just dump the traffic into the "closest" or
"currently known" outgoing gateway. If you need load-balancing, fairness or
need to care for certain restrictions of gateways, you need additional
information and protocol parts

> Thank you for any help on default route.  In your reply, please be 
> aware that I’m the co-chair of the IDR (BGP) working group.

I don't think the 0/0 route should be that special... there are other kinds
of prefixes that might be relevant for AODVv2 too, for example /64 prefixes
in IPv6 networks to allow each AODVv2 node to announce a complete subnet
attached to the mesh node.

Henning Rogge
--
Diplom-Informatiker Henning Rogge , Fraunhofer-Institut für Kommunikation,
Informationsverarbeitung und Ergonomie FKIE Kommunikationssysteme (KOM)
Fraunhofer Straße 20, 53343 Wachtberg, Germany
Telefon +49 228 9435-961,   Fax +49 228 9435 685
mailto:[email-masked] http://www.fkie.fraunhofer.de

---

From: Henning Rogge <[email-masked]>
Date: Mon, 14 Jan 2013 15:40:39 +0100

> from ISIS, OSPF, or OLSR.

Yes.

> Did I understand correctly?

I say we should do it right (allow any kind of prefix, maybe with some 
necessary administrative rules) or postpone it to an extension draft.

Building a special case for a single internet gateway (and no other 
prefixes) sounds like a bad idea.

Henning Rogge

---

From: "Susan Hares" <[email-masked]>
Date: Mon, 14 Jan 2013 09:51:21 -0500

Henning:

I agree you want to do the insertion of externals into a reactive protocol
carefully.

Having built BGP-3, I tend to agree with you from the protocol coding
viewpoint that 0/0 as a unique case is not a good idea.   

However, there are many places in the Internet operationally which use a
default-free zone.  
Are there operational issues that would lead us to just the 0/0 prefix?
I've not seen them listed on the mail list. 

Sue 

-----Original Message-----
From: Henning Rogge [mailto:[email-masked]] 
Sent: Monday, January 14, 2013 9:41 AM
To: Susan Hares
Cc: [email-masked]
Subject: Re: [manet] Technical issue 3: default route (Route.pfxlen)

Yes.

Henning Rogge