Subject: [manet] DLEP and multi-hop neighbours

From: "Rick Taylor" <[email-masked]>
Date: Fri, 30 Mar 2012 11:34:57 +0100

As part of our on-going work with DLEP, we have discovered a problem
with the definition of a neighbour on a DLEP session.

In a smart meshing radio network, each DLEP radio could report all its
multi-hop link-neighbours as DLEP neighbours.  This is valid according
to the wording of draft-02, but is misleading to any router attempting
to discover the topology of the actual radio network.

A proposed resolution to this problem is rather than force only 1-hop
neighbours to be reported via DLEP, add an extra 'hop-count' TLV to the
NeighbourUp message.  Of course adding an extra TLV just for a single
octet seems like a lot of extra data, perhaps the RFC5444 gurus can
suggest a more elegant method? Or perhaps the absence of the hop-count
TLV implies a 1-hop neighbour?

Rick Taylor

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From: "Powell lll, Nelson" <[email-masked]>
Date: Fri, 30 Mar 2012 13:32:27 +0000

Rick,
I'm not sure it is a "problem" so much as it is a feature. Allowing a radio to behave as a "neighbor" allows for more intelligent waveforms to handle the routing internally. If a hop-count were added, I would imagine that should be more an optional TLV, as intelligent waveforms may use latency in a similar manner.

Nelson

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Rick Taylor
Sent: Friday, March 30, 2012 6:35 AM
To: [email-masked]
Cc: [email-masked]
Subject: [manet] DLEP and multi-hop neighbours

Rick Taylor
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From: "Rick Taylor" <[email-masked]>
Date: Fri, 30 Mar 2012 15:07:43 +0100

Nelson,

Okay, "problem" might be too strong, I agree with "feature".

I do understand why radios might behave in this manner, and don't want
to see it actively prevented, but a slightly simple/basic radio mesh-net
(such as we have seen with the kit we are using) reporting all
neighbours as fully connected although the reality is traffic is routed
via an elected cluster-head can result in routers subjecting the
cluster-head to a massive burst of traffic, which the routers were
actively trying to avoid doing.

In summary, I would like to see some kind of notification TLV if the
reported neighbour is on the far end of a 'dog-leg' via another reported
neighbour, i.e. the route to the neighbour is not 'direct' (for a
relatively loose definition of direct). I was suggesting a hop-count TLV
as a mechanism, but if you or anyone else on the radio-side of DLEP has
a better suggestion, go for it!

Rick Taylor

-----Original Message-----
From: Powell lll, Nelson [mailto:[email-masked]] 
Sent: 30 March 2012 14:32
To: Rick Taylor; [email-masked]
Cc: [email-masked]
Subject: RE: DLEP and multi-hop neighbours

Rick,
I'm not sure it is a "problem" so much as it is a feature. Allowing a
radio to behave as a "neighbor" allows for more intelligent waveforms to
handle the routing internally. If a hop-count were added, I would
imagine that should be more an optional TLV, as intelligent waveforms
may use latency in a similar manner.

Nelson

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Rick Taylor
Sent: Friday, March 30, 2012 6:35 AM
To: [email-masked]
Cc: [email-masked]
Subject: [manet] DLEP and multi-hop neighbours

Rick Taylor

---

From: Teco Boot <[email-masked]>
Date: Fri, 30 Mar 2012 16:30:17 +0200

> a better suggestion, go for it!

Yes, we try to get rid of min-hop based routing. That is where 
DLEP comes in. I understand the sub-IP layer multi-hop routing,
but I think you should push getting useful info from such "modems".

Another example would be a 2-hop satcom link, where hub is 1-hop
and other spokes are 2-hop (seen from a spoke).

Let's try to get the link metrics already defined in dlep-02 from
these devices. Hop-count in a heterogenous network gets messy easily.

Teco

---

From: "Rick Taylor" <[email-masked]>
Date: Fri, 30 Mar 2012 16:05:00 +0100

Okay, as an alternative suggestion to hop-count, how about a 'via' TLV?
I.e. Neighbour Y is a neighbour with metrics {m1..mN} but traffic to Y
goes via X.

The problem I see with 'via' is in a complex radio mesh net, one could
have reported neighbours more than 2 hops away.

I understand the need to move away from hop-count as a routing metric,
but there must exist a way for routers to discover the topological
relationships between neighbours.  Perhaps it is simpler therefore to
say "do not report 2 hop neighbours"?

Rick Taylor

-----Original Message-----
From: Teco Boot [mailto:[email-masked]] 
Sent: 30 March 2012 15:30
To: Rick Taylor
Cc: Powell lll, Nelson; [email-masked]; [email-masked]
Subject: Re: [manet] DLEP and multi-hop neighbours

Teco

---

From: "John Dowdell" <[email-masked]>
Date: Fri, 30 Mar 2012 16:58:20 +0100

For me, routing traffic over DLEP-based networks should get away from
min-hop strategies, but should be based on the attributes of the
connections between nodes (however many hops that takes).

However, when you want to manage the bandwidth across your network, you
need to understand the topology of the network.

An example: A, B and C are network nodes, each with a router and radio.

A ------ B -------- C,  and C has no direct connection to A because of
obstruction or insufficient range.

Suppose the bandwidth A to B is 10 units, and the bandwidth B to C is 5
units.

Suppose radios A, B and C reported all N-hop neighbours without
reporting hop count or the address of the node they were relaying
through. The DLEP reports at A might show to B as 10 units and to C as 5
units. IMHO I would like to see neighbours reported with relay
address(es) rather than hop counts. Oops, this starts to look like a
routing table .... is that the job we are trying to do here?

When policing traffic bandwidth at A towards B, the policer will believe
there are 10 units available. Towards C, the policer will believe 5
units are available, without understanding that the 5 units to C are
part of the 10 units between A and B.

Reporting latency without hop count is not a problem, because the values
are additive, but for bandwidth there is an issue. Link Quality and
Resources metrics have their own issues.

John 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Teco Boot
Sent: 30 March 2012 15:30
To: Rick Taylor
Cc: [email-masked]; [email-masked]
Subject: Re: [manet] DLEP and multi-hop neighbours

Teco

---

From: "Cole, Robert G CIV USARMY CERDEC (US)" <[email-masked]>
Date: Fri, 30 Mar 2012 17:01:44 +0000

Why would we like " for more intelligent waveforms to handle the routing internally" ?

Thanks,  Bob

----- Original Message -----
From: Powell lll, Nelson [mailto:[email-masked]]
Sent: Friday, March 30, 2012 01:32 PM
To: Rick Taylor <[email-masked]>; [email-masked] <[email-masked]>
Cc: [email-masked] <[email-masked]>
Subject: Re: [manet] DLEP and multi-hop neighbours

Rick,

Nelson

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Rick Taylor
Sent: Friday, March 30, 2012 6:35 AM
To: [email-masked]
Cc: [email-masked]
Subject: [manet] DLEP and multi-hop neighbours

Rick Taylor

---

From: "Ivancic, William D. (GRC-RHN0)" <[email-masked]>
Date: Fri, 30 Mar 2012 12:31:20 -0500

My experience is that you want to either let the radios do routing at layer-2 or routers do routing at layer-3. If you have a split, the two systems will fight each other.

Since manets are targeted for first responders and the military and other edge networks, anything overly complex is not practical to deploy.   .... and we haven't event touched upon security requirements in a military setting.

- Will

On Mar 30, 2012, at 1:01 PM, Cole, Robert G CIV USARMY CERDEC (US) wrote:

Thanks,  Bob

----- Original Message -----
From: Powell lll, Nelson [mailto:[email-masked]]
Sent: Friday, March 30, 2012 01:32 PM
To: Rick Taylor <[email-masked]<mailto:[email-masked]>>; [email-masked]<mailto:[email-masked]> <[email-masked]<mailto:[email-masked]>>
Cc: [email-masked]<mailto:[email-masked]> <[email-masked]<mailto:[email-masked]>>
Subject: Re: [manet] DLEP and multi-hop neighbours

Rick,

Nelson

-----Original Message-----
From: [email-masked]<mailto:[email-masked]> [mailto:[email-masked]] On Behalf Of Rick Taylor
Sent: Friday, March 30, 2012 6:35 AM
To: [email-masked]<mailto:[email-masked]>
Cc: [email-masked]<mailto:[email-masked]>
Subject: [manet] DLEP and multi-hop neighbours

Rick Taylor
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******************************
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---

From: Teco Boot <[email-masked]>
Date: Fri, 30 Mar 2012 21:08:34 +0200

> connections between nodes (however many hops that takes).
Min-hop may work with homogenous networks where links are near to perfect.
This is rare in a MANET, where DLEP is used.

> obstruction or insufficient range.
Because this network is sub-IP, for us it is a flat L2 network.

> routing table .... is that the job we are trying to do here?
I think that on A, neighbor B is reported with lower metrics as C.

> part of the 10 units between A and B.
Good example why I think DLEP flow control is a bad idea.

> Resources metrics have their own issues.
Good example why additive dimensionless metrics make live easy.

Teco

---

From: Teco Boot <[email-masked]>
Date: Fri, 30 Mar 2012 21:14:45 +0200

> My experience is that you want to either let the radios do routing at layer-2 or routers do routing at layer-3. If you have a split, the two systems will fight each other.
+1

> Since manets are targeted for first responders and the military and other edge networks, anything overly complex is not practical to deploy.
+1
But some are playing with it. Or struggling :-)

>   .... and we haven't event touched upon security requirements in a military setting.
I guess we (IETF) won't touch security for military...
Now I put money on my horse.

Teco

---

From: "Das, Subir" <[email-masked]>
Date: Fri, 30 Mar 2012 20:29:45 +0000

I have the same question. I assume we are consideri
L3 routing here not 

Sent from my iPhone

---

From: Henning Rogge <[email-masked]>
Date: Sat, 31 Mar 2012 10:49:10 +0300

On Fri, Mar 30, 2012 at 22:14, Teco Boot <[email-masked]> wrote:
> My experience is that you want to either let the radios do routing at
> layer-2 or routers do routing at layer-3. If you have a split, the two
> systems will fight each other.
>
> +1

Yes. Having a layer 3 routing over a layer 2 mesh can be a nightmare.

> Since manets are targeted for first responders and the military and other
> edge networks, anything overly complex is not practical to deploy.
>
> +1

If DLEP only communicates between the radio and the (ethernet-)
attached router, there is not much security necessary for this control
path.

Henning Rogge

-- 
Steven Hawkings about cosmic inflation: "An increase of billions of
billions of percent in a tiny fraction of a second. Of course, that
was before the present government."

---

From: "Das, Subir" <[email-masked]>
Date: Sat, 31 Mar 2012 15:17:23 +0000

Sorry for my incomplete message.. 

I assume we are considering L3 routing not L2 routing. 

-Subir 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Das, Subir
Sent: Friday, March 30, 2012 4:30 PM
To: Cole, Robert G CIV USARMY CERDEC (US)
Cc: [email-masked]; [email-masked]
Subject: Re: [manet] DLEP and multi-hop neighbours

Sent from my iPhone

On Mar 30, 2012, at 1:02 PM, "Cole, Robert G CIV USARMY CERDEC (US)" <[email-masked]> wrote:

> neighbours to be reported via DLEP, add an extra 'hop-count' TLV to 
> the NeighbourUp message.  Of course adding an extra TLV just for a 
> single octet seems like a lot of extra data, perhaps the RFC5444 gurus 
> can suggest a more elegant method? Or perhaps the absence of the 
> hop-count TLV implies a 1-hop neighbour?
> 
> Rick Taylor

---

From: Henning Rogge <[email-masked]>
Date: Sat, 31 Mar 2012 18:27:40 +0300

>From the draft:

> DLEP assumes that participating clients appear to the server as a
> transparent bridge - specifically, the assumption is that the
> destination MAC address for data traffic in any frame emitted by
> the server should be the MAC address of the next-hop router or end-
> device, and not the MAC address of any of the intervening clients.

If the "Server/Radio/Interface" is a layer 3 router, why should it need DLEP?

Henning Rogge

---

From: "Das, Subir" <[email-masked]>
Date: Sat, 31 Mar 2012 15:59:26 +0000

I do not think that Radio or client interface is considered as a L3 router but Server is. 
Also draft says: "DLEP is independent of the underlying link type and topology." 

_Subir 

-----Original Message-----
From: Henning Rogge [mailto:[email-masked]] 
Sent: Saturday, March 31, 2012 11:28 AM
To: Das, Subir
Cc: Cole, Robert G CIV USARMY CERDEC (US); [email-masked]; [email-masked]
Subject: Re: [manet] DLEP and multi-hop neighbours

> destination MAC address for data traffic in any frame emitted by the 
> server should be the MAC address of the next-hop router or end- 

Henning Rogge

On Sat, Mar 31, 2012 at 18:17, Das, Subir <[email-masked]> wrote:
> Of Das, Subir
>> In a smart meshing radio network, each DLEP radio could report all 
>> its multi-hop link-neighbours as DLEP neighbours.  This is valid 
>> according to the wording of draft-02, but is misleading to any router 
>> attempting to discover the topology of the actual radio network.
>>
>> single octet seems like a lot of extra data, perhaps the RFC5444 
>> gurus can suggest a more elegant method? Or perhaps the absence of 
>> the hop-count TLV implies a 1-hop neighbour?
>>
>> Rick Taylor

--
Steven Hawkings about cosmic inflation: "An increase of billions of billions of percent in a tiny fraction of a second. Of course, that was before the present government."