Subject: RE: SCTP for MANETs

From: Phillip Neumiller <[email-masked]>
Date: Tue, 18 Dec 2001 09:13:07 -0500

Hi Charlie,

> -----Original Message-----
> From: Charles E. Perkins [mailto:[email-masked]]
> 
> > What needs to be carefully examined is how you can use SCTP 
> as a tool or aid
> > in the construction of ad hoc networking protocols.
> 
> I'm not intimately familiar with SCTP, but insofar as one node would
> have to establish a connection with another node before message data
> could be transacted, I think SCTP is a poor choice for  control messages.
> If SCTP has a "UDP with retransmission" choice, I would be happier.

That is one of the nice features of SCTP.  The association can be made
with another bindx() call rather quickly.  So what can be done is to bundle
together IP addresses are they "discovered" by moving MN when they "see"
beacons/pilots/etc.  SCTP was first put over UDP and started out as UDP
with retransmission.  Its now a full fledeged transport with its own
protocol ID giving you much better featers than UDP with re-XMIT with
the same light weight.

> I think so too.  This actually has been part of my motivation for
> continuing with AODV.  I truly believe that loop-free on-demand
> Distance-Vector routing is a _very_ scalable and economical
> alternative for arbitrary routing purposes -- and, here, arbitrary
> explicitly _includes_ ad hoc.

Do you believe that AODV can replace OSPF, BGP, RIP, and all other routing
protocols?  Do you think the Internet would be a better place if we
did that?  I tend to agree, but when I look at the tall wall of legacy
my knees shake.  RIP has loops and look how far it got!!!

> 
> >                                    (this will probably occur
> > when Quantum Mechanics and Relativity have been unified). 
> 
> I thought Hawking's work did this, especially regarding the way that
> subatomic particles leak from black holes.

There are many theories, but measurement validations to 12 decimal places
have only been made in "straight" quantum physics and relativity.  I wonder
if quantum entanglement based routing is the answer?

> I gather this is mainly targeted for data streams, not 
> control messages...?

SCTP was designed with control message in mind.  I don't understand your 
hesitation here.

> 
> There is a huge difference between multi-homing and route diversity,
> generally speaking.  However, if you meant to use the route diversity
> by assigning different routes to different IP addresses of the
> _same destination_, then I would agree that this is an interesting
> possibility.  It seems to me that it would be most useful if the
> multiple IP addresses were associated with different media interfaces.

The SCTP association can dynamically add and drop IP addresses much the
way a CDMA system adds and drops call legs with its TADD/TDROP timers.  
You could think of the set of IP address in the association as the 
active set.
  > 
> > + This is really important.  It give the wireless router 
> the ability to
> > quickly switch routes WITHOUT BREAKING THE END-TO-END 
> STREAM associations!
> 
> Is this all part of the same bullet item, or did you mean to have two
> bullet items?
> 
> For route updates, maybe it isn't so applicable to on-demand systems.
> For keep-alives, I think more work is needed, but this behavior would
> have to be heavily moderated, to the point of being eliminated when
> there is actual traffic.  Or maybe SCTP already does this.  But then
> some applications would not care.  Maybe the route between 
> two endpoints
> would only have the heartbeat mechanisms if there are nonzero SCTP
> transport connections between them.

The keep alives are adjustable and this is an optimization over Zygmut's
proposal I believe.  His proposal sends data over all the paths to get
diversity, whereas SCTP can use its best path and keep alternative 
routes alive for hot fail over.  Alternatively, it can load balance across
the routes.

Best Regards,

Phil
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---

From: "Charles E. Perkins" <[email-masked]>
Date: Tue, 18 Dec 2001 10:31:39 -0800

Hello Phil,

> protocol ID giving you much better featers than UDP with re-XMIT with

Can we specify the number of retransmissions, and the retransmission
interval?

> my knees shake.  RIP has loops and look how far it got!!!

One thing about an ad hoc network is that it needs a routing protocol
that converges quickly.  One of the things about "Internet" routing protocols
is that they have problems because they don't converge quickly enough.
That is a problem for which I think we may have something to offer.

I'm not part of the BGP priesthood, but I know that one of the things
that makes it drastically complicated is the number of bizarre policy
knobs that are built into it.  This is an area where AODV (currently,
and for the near future) offers nothing, like all other manet protocols.
Worse yet, it seems to me that "Internet" protocols don't care as much
about hop count as "manet" protocols do.  On the other hand, it's all we
have for now to compare routes (well, not exactly, but close enough for
the discussion in this paragraph).

> if quantum entanglement based routing is the answer?

Now I know that you are yanking my chain :-)  Maybe the answer (for routing)
has more to do with the intersection of Kama Sutra with wireless graph theory?

> SCTP was designed with control message in mind.  I don't understand your

O.K.  I'll keep this in mind.  I reckon that at least the Route Discovery
flood stuff would not fit well within the SCTP mold.  I would not expect
for SCTP to be used to maintain neighbor sets (for protocols that care
about such things) or connections to lists of precursors (for something
AODV specific).  However, if "bindx()" works without any participation
from the other end, I might be pleasantly surprised on this point!

> You could think of the set of IP address in the association as the

If you add several hosts to an SCTP association, without any participation
from the other end, is it like a single-source multicast group?

Regards,
Charlie P.

---

From: "Jim Fleming" <[email-masked]>
Date: Tue, 18 Dec 2001 13:51:39 -0600

----- Original Message ----- 
From: "Phillip Neumiller" <[email-masked]>
To: "'Charles E. Perkins'" <[email-masked]>; "Phillip Neumiller" <[email-masked]>
> protocol ID giving you much better featers than UDP with re-XMIT with

Can't SCTP still be encapsulated in UDP ?
With intra-galactic transports only having ICMP, TCP and UDP
we use the other 6 bits of the protocol field for addressing.

This may help...
http://www.dot-biz.com/IPv4/Tutorial/
http://www.RepliGate.net

The Netfilter Project: Packet Mangling for Linux 2.4
http://netfilter.samba.org

Jim Fleming
http://www.IPv8.info
IPv16....One Better !!

---

From: Yih-Chun Hu <[email-masked]>
Date: Tue, 18 Dec 2001 14:52:21 -0500 (EST)

Hi Phil and Charlie,

>and for the near future) offers nothing, like all other manet protocols.

I think DSDV could be extended to a path-vector protocol that allowed the
use of varied policies. DSR to some slight extent also is capable of
policy routing, since the source has the opportunity to choose which of
the potentially several routes in its cache to use. I haven't thought much
about how one could add policy-based routing to AODV...

>the discussion in this paragraph).

That, and it's significantly more important in a manet running over
protocols such as IEEE 802.11 due to full-power RTSs and CTSs. In a wired
network, if you wind up routing along a suboptimal route, it does no harm
to anyone who doesn't share that same set of links. In wireless, you're
spraying RF energy all over the place and affecting all your neighbors.

While a grand unified ipv6 routing protocol that replaces mip and manet
would be nice in theory, the business realities of peering and transit
agreements, combined with the technical issues of location privacy,
routing security, and limited memory in routers (imagine several thousand
/1 routing table entries, each for a single mobile node) seems to limit
such approaches to smaller, trusted networks.

Yih-Chun

---

From: Chip Elliott <[email-masked]>
Date: Tue, 18 Dec 2001 15:00:33 -0500

> > if quantum entanglement based routing is the answer?

Speaking as one of those lucky few who have branched out from
MANET routing protocols to quantum-entanglement based routing
(really!).... I'd say that, no, quantum entanglement based routing
is not the answer... alas.....

For fun on quantum cryptographic networks, check out....

       quantum.bbn.com

Cheers to all mad scientists,

Chip Elliott

---

From: "David R. Gervais" <[email-masked]>
Date: Thu, 20 Dec 2001 10:47:16 -0500

Phillip,

	Comment and rant inline.

> my knees shake.  RIP has loops and look how far it got!!!

I totally agree with you. I think that AODV, along with OLSR, are two 
distinct canidates for wired networking...and I think that they SHOULD 
be implimented. However, current implementations do not allow for 
multiple connections (look at the MITRE Mobile Mesh routing code by 
Kevin Grace...his code supports multiple interfaces, maybe this'll 
provide a code base for other people implementing mobile routing 
protocols?) and this limitation  must be addressed if mobile routing 
protocols are to take over wired protocols (as they should). This will 
not only make the web more stable, it will make the web more 
autonomous....which is definately a good thing.

Is anyone out there implementing AODV or OLSR for multiple interfaces? 
If so, I'm definitely interested in seeing some of your work as I'm sure 
alot of other people would be.

*** SIDE RANT ABOUT MOBILE ROUTING PROTOCOLS

Another problem with these protocols is the lack of compatibility. For 
example, lets say I have a mobile network and it comes into contact with 
a gateway into a fixed network (say a computer running AODV on one 
interface and a static route into the internet on another). How do 
packets tunnel through the gateway to get to the intended destination? 
No current implementations offer heterogeneity. Also, how do you manage 
IP address assignments in a mobile network that **might** have a fixed 
architecture??? And then the question becomes can you? Mobile IP 
addresses some of these concerns, but definately not all of them. A user 
still has to register with the gateway and it assumes that the path 
for receiving is the same path as transmission (meaning if 10.0.0.1 
sends a TCP message via 11.0.0.1, which is running mobile IP, then an 
ack must come back via 11.0.0.1). This is a problem when that internet 
connection is via satellite or a high latency link and the mobile node 
can roam far in three seconds (ie. an airplane to airplane link).

Some of these IP assignment problems need to be addressed (or addressed 
better) for mobile routing algorithms to become popular. If anyone has 
any information as to who is doing work in this area and what documents 
have been publish on the subject, I would be greatly appreciative.

I'm sorry for the rant....this is just something that always bothered me 
and since I really want to see MANETS succeed, I hope that these 
questions can be answered in the years to come. Thanks  for your 
feedback and taking the time to read my rant :-)

-- 
+++---
David Gervais
Communications Engineer
MITRE Corporation

Email: [email-masked]
Phone: (781) 271-2807

---

From: "Fred L. Templin" <[email-masked]>
Date: Thu, 20 Dec 2001 11:35:59 -0800

David and Phillip,

"David R. Gervais" wrote:
> I totally agree with you.

On this point, I also agree. The goal of developing the most efficient
MANET routing protocol possible should yield candidate replacements for
legacy protocols now at work in the Internet. Increased efficiency in
routing protocols is *always* an advantage - regardless of how robust
the underlying physical link layer. Like any other attempt to convert
a deeply-entrenched customer base, however, such a migration would
require a significant coexistence and transition phase. (See the
NGTRANS WG for an example of the magnitude of effort required to
manage such a transition.)

Fred
[email-masked]

---

From: Vijay Devarapalli <[email-masked]>
Date: Thu, 20 Dec 2001 11:53:18 -0800

hi David,

reply to your rant. take a look at

http://www.ietf.org/internet-drafts/draft-wakikawa-manet-globalv6-00.txt
http://www.ietf.org/internet-drafts/draft-royer-manet-globalv4-00.txt

they talk about address assignment, gateway router 
discovery and much more....

Vijay

---

From: "Philippe Jacquet" <[email-masked]>
Date: Fri, 21 Dec 2001 11:35:06 +0100

Cedric Adjih is currently implementing multiple interface OLSR, I think he
will be very interested in this discussion.

Philippe