Subject: Re: Comments on draft-ietf-ipngwg-addrconf-privacy-00.txt

From: "Steven M. Bellovin" <[email-masked]>
Date: Fri, 15 Oct 1999 16:02:23 -0400

I'm replying to a couple of posts from different individuals here.

> >Customer could be a complete subnet, but more typically in the domestic mark
> et
> >would be a single node.  For ISP models that need to count bytes and packets
> >for customer billing, if an individual node can't be tracked, there is a
> >problem.
> 
> The single-node customer is just an (uninteresting?) special case, which
> will become less dominant over time, as people move from having one PC at
> home to having a network (or internetwork) of PCs and other devices at
> home.  Those ISPs that feel the need to bill by byte or packet can do so
> based on customer prefix -- whether one host sends two packets or two hosts
> send one packet each, it's the same cost to the ISP.

Billing isn't the issue; authorization is.  Anyone can (and has) hooked a box 
up to a cable segment.  Verifying that that customer is authorized -- and that 
includes "has paid their most recent bill, and not offended the AUP by 
ping-flooding their neighbors" -- is essential before they're allowed to send 
or receive packets.

> Perhaps some more enlightened members of the list would be able to shed light
> on what is current and best practice in the cable modem internet industry.
> Are these set top boxes really that smart?  

Today's boxes are more like bridges than routers -- but yes, they're pretty 
smart and getting smarter.

The cable modems I'm familiar with don't act like Ethernet transceivers.  A 
cable segment is logically composed of an upstream section and a downstream 
section.  When you send a packet to your neighbor, it goes all the way 
upstream to the CMTS (cable modem termination system), before being 
retransmitted downstream.  All sorts of filtering can and does take place at 
the CMTS.  Traffic is often link-encrypted today, and will always be 
link-encrypted in the very near future.

As far as cost is concerned -- yes, everyone wants everything to be cheap.  
But the most expensive thing is providing customer care, which is why NATs are 
being rejected by some ISPs (broken applications make customers call up and 
complain, and it takes a Tier II or Tier III support person to realize that 
it's a NAT-induced failure).  Dealing with customer complaints about their 
machines being hacked -- even if the fault is really their drain-bamaged host 
software or their own (lack) of system administration skills -- is expensive, 
too.

		--Steve Bellovin

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