Re: [Starlink] Measuring the Satellite Links of a LEO Network

[Alexandre Petrescu <alexandre.petrescu@gmail.com>]

this is an issue for 6MAN WG at IETF, but this is the text with the 
issue in the paper:

> From the user device or customer router at 192.168.1.1,
> we can reach its GS gateway at 100.64.0.1 (or equivalently
> fe80::200:5eff:fe00:101 for IPv6)

That IPv6 link-local address has an 'ff:fe' in it; the prefix is 'fe80' 
and the rest is an 'Interface ID', in RFC parlance.

That IID should be more random in its appearance.  It is called an 
'opaque' IID, and specified in RFC 7217 "Stable and Opaque IIDs with 
SLAAC" of year 2014.

That IPv6 address corresponds to earlier forms of these IIDs (RFC2464 of 
year 1998); they had that IID to be derived from a 48bit MAC address and 
inserted an 'ff:fe' string in it to become 64bit.

Most embedded linux platforms (v2.x kernels?) still use that ff:fe.  
Migrating these kernels is sometimes very difficult.  One might not want 
to migrate an kernel to a bloated and slower v3 or higher just for that 
little 'ff:fe'.  Maybe one wants to migrate just its IPv6 stack, but 
it's not easy.

The reason of making this IID more opaque is to resist scanning 
attacks.  A scanning attack is when a user might have somehow an 
illegitimate starlink terminal and tries to connect to the legitimate 
starlink network.  Part of that trying is to know the IP address of the 
next hop.  With IPv6 it comes down to testing all these addresses.  If 
they have a constant 'ff:fe' in them, it is easier to find them by brute 
force than if they were opaque.  It is also true that if in IPv4 that 
next hop is always the same then the easiest attack is to simply use 
IPv4 instead of IPv6.  But this 'opaqueness' of the IID in the IPv6 ll 
address might still be needed when IPv4 is get rid of.

This could be discussed at IETF, could be suggested to starlink to 
upgrade, etc.

Alex

Le 12/02/2024 à 07:59, J Pan via Starlink a écrit :
> http://pan.uvic.ca/webb/viewtopic.php?p=124670#p124670 to appear at
> ieee icc 2024. feedback welcome, especially during the camera-ready
> stage this week. thanks!  -j
> --
> J Pan, UVic CSc, ECS566, 250-472-5796 (NO VM), Pan@UVic.CA, Web.UVic.CA/~pan
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