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Re: old GSE idea

On donderdag, apr 17, 2003, at 01:29 Europe/Amsterdam, David Conrad wrote:

I think the simplest solution is to make the lower 64 bits globally unique.


This breaks autoconfiguration.





Only in as much as the 64 bits used in auto-configuration are not 
globally unique. How is this that much different than duplicate IP 
addresses in a WAN or duplicate MAC addresses on a LAN (both in terms 
of detection and remedy)?  It should be treated as the error condition 
it is, not a normal state of affairs.



MAC address collisions are not uncommon. Some time NIC vendors screw 
up, and some times people who should know better don't do the right 
thing. Just yesterday I had a problem with a layer 3 switch that uses 
the same MAC address for all of the virtual (VLAN) IP interfaces. And 
then there is stuff like privacy protection by randomly selecting the 
lower 64 bits.



The problem is that on a LAN, you can do DAD, but doing that world wide 
each time you connect to the network is no fun.




I think we need at least 40 bits for the organization ID so that 
leaves just 24 bits for link-local use,




Why put location back into identity?  In my view, endpoint identifiers 
are 'names'.  They are a flat, undifferentiated (from the network 
perspective, administratively, you may want some hierarchy) identifier 
space.



This is going to be a problem if you want to look these up in a 
distributed database. We really need a hierarchy for something like 
this.




So what happens when a link goes down?





Assuming you are asking about the multi-homed destination case,the 
naive approach would be to have the source core/edge boundary 
forwarder notice the link is down via 'traditional' methods (BGP 
re-convergence, ICMP network unreachable, whatever)


Obviously this stuff isn't going to be in BGP.  :-)

A large percentage of network problems don't generate unreachables.

So we don't get to be naive here.




Other solutions in this area provide the same benefit without 
breaking link local behavior,




How do GSE-like solutions break link local behavior?




I mean autoconfiguration and similar stuff that escapes me at the 
moment...




Given the state of routing security (that is, the ability to insert 
pretty much any prefix into the routing system) I personally do not 
believe the latter concern is significantly worsened by something 
like GSE and, in any event, this issue would be addressed by 
deployment of IPSEC.




How is IPsec going to help you if the packets are rerouted over the 
null0 interface?




Sorry, don't follow.




If an attacker gets to reroute your traffic, then they presumably also 
get to route in into oblivion. So IPsec doesn't solve problems in the 
routing system.




Don't forget about the actual failover. Also quite solvable, but not 
a trivial problem.




The difficulty in failover is detecting failover is necessary at the 
source.  One possible solution would be to have the alternative 
locators kept with the packet in transit as an IPv6 option.



Yes, Marcelo Bagnulo has a draft out on this, if I remember correctly.



This helps but doesn't really solve the problem of dead layer 2 
networks where the IP-speaking boxes at both ends don't see there is 
something wrong.




The problem I have with GSE and its derivatives is that it is 
self-contained and doesn't provide hooks either forward or backward.




I don't understand this statement.




What I mean is that you need to implement GSE on both ends before it 
will do you any good. 15 second explanation of MHAP: hosts use PI 
addresses, but these addresses are replaced with PA addresses in 
transit. With MHAP or something similar, you don't have to upgrade all 
hosts, which is better, none of the routers, which is much better, and 
you can also start using the PI space immediately and then move in the 
MHAP boxes later. That's what I mean by hooks backward.



I think hooks forward are possible by not hardcoding the exact 83 bits 
we look at into the modified stacks but by making this more generic so 
we can support 160 bits or 64 bits out of 128 or whatever at some later 
date.




It would be great if it could be part of a bigger picture, where we 
can upgrade from what we have today, to something a bit better, to 
GSE++, to a clean architecture where we really get to drop in new 
protocols for each layer like the OSI guys always promised we could.




I believe the first step in any reasonable evolution will be to 
separate identifier from locator.  Given realities of the market and 
the IETF, small steps are more likely to get forward motion than giant 
leaps.



I'm not saying we should implement huge steps, but it would be good if 
the small steps we implement get us closer to a long term goal.