Subject: Re: support for packet drop priority

From: [email-masked] (Konstantinos Dovrolis)
Date: Sat, 31 Jan 1998 00:42:55 -0600

> 
> So exactly what is the "known solution" for making best-effort sources adapt
> to their share of the bottleneck resource, and when will it be ubiquitously
> deployed in the Internet?
> 

Hi Steve,

I would like to know what the group thinks about the following idea.

Although we usually talk about non-adaptive sources or users,
we actually mean applications. The truth is that the vast majority of the
Internet traffic today is created by less than a dozen of applications.
Right? Is there any good reason that we will see this changing? 
I don't think so. Perhaps the dozen will become 100 but this is 
still "observable and controllable".

So, suppose that each ISP makes a "black list" of the non-adaptive
applications, and the routers at all the user-network or network-network
ingress points classify the arriving traffic based on the port numbers.
I mean, suppose that user (or network) X has subscribed for a higher-service
class (say based on DP) with the adjacent network Y. The contract is
that this class can only be used if the source or destination port numbers
belong to this list (actually this would be the "white list").
The traffic agreements are only bilateral and the policing
is not per-flow or per-user, but just based on the port number of each
packet (I am assuming here that 99% of the IP traffic is and
will remain TCP or UDP, so we can talk for port numbers for each IP packet).
The port lookup can be done in parallel with the forwarding decision,
so I don't think that it would make the router any slower.

In this case, users have the incentive to use adaptive applications
(because the alternative is to use non-adaptive applications at the
basic service class, and consequently to get losses of the size that we
get today).

Application vendors also have the incentive to write adaptive applications,
because these are the applications of the "white list" that people will
be more willing to buy and use. Second, these applications will not
have to compete in an opportunistic way with non-adaptive applications,
so they can be adaptive, without having the "looser's mark".

Networks also have the incentive to do this port/application classification,
because in this way they can provision their higher-service
class better and isolate it from the "bad guys". If a high-service
class is adequately provisioned, restricted only to adaptive applications,
and isolated from the non-adaptive applications, the network providers and 
ISPs will also feel more comfortable to ask for a higher price-rate for 
the higher-service class from the users (I am talking about
flat-rates; nobody wants to count bytes).

Do you see the cycle here? Users and their quality/economic incentives,
application vendors, ISPs and network providers, router vendors. 
If one of them only makes the move, nothing will happen. 
They all have to change something in their business simultaneously,
for the above ideas to be realized. 

I know that IP-sec is supposed to encrypt the port numbers, but
is this the only problem with the port-based classification? I have heard 
that IP-security is not really going to be deployed any time soon (i.e. it
will never be used...)

So is there another flaw?

Thanks in advance for any comments,

Constantinos

---

From: Jon Crowcroft <[email-masked]>
Date: Sat, 31 Jan 1998 15:55:21 +0000

In message <[email-masked]>, Konstantinos Dovrolis ty

 >>I would like to know what the group thinks about the following idea.
 
 ...a lot of ISPs already do this....

 >>so I don't think that it would make the router any slower.

basicaly, this is much the philosphoy behind Van's diffserve model -
if you have dumb, non adaptve applications, then rent a "CBR pipe"
from your ISP, otherwise adapt....

RED does fairness in latter case, and peak rate police with discard
does it in the former, with the price making it unlikely too many
people subscrie to the expensive to implement and provision "higher"
grade premium...
 
 >>Thanks in advance for any comments,

 cheers

   jon

---

From: Wu-chang Feng <[email-masked]>
Date: Sat, 31 Jan 1998 16:15:21 -0500

> Networks also have the incentive to do this port/application classification,

Sounds like CBQ where the class, in this case, is based on the port number.

Wu

---

From: Steve Deering <[email-masked]>
Date: Mon, 2 Feb 1998 16:46:34 -0800

At 10:42 PM -0800 1/30/98, Konstantinos Dovrolis wrote:
> we actually mean applications.

Sometimes the the responsibility for adapting belongs to the application
(e.g., some, but not all, apps built on top of UDP); other times it belongs
to a layer beneath the application (e.g., TCP or NFS).

> ingress points classify the arriving traffic based on the port numbers.

Just because the port number says "FTP" doesn't mean the source of that
traffic is well-behaved -- it might be using an implementation of TCP that
has been hacked to be overly aggressive.

Also, if you blacklist some ports, the apps using those ports will just
migrate to using non-blacklisted ports.

It's the actual, observable behavior that matters, not the port numbers
that are being used.

Steve