Re: [Autoconf] new charter

Carlos Jesús Bernardos Cano <cjbc@it.uc3m.es> Sat, 28 February 2009 13:43 UTC

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From: Carlos =?ISO-8859-1?Q?Jes=FAs?= Bernardos Cano <cjbc@it.uc3m.es>
To: Teco Boot <teco@inf-net.nl>
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Date: Sat, 28 Feb 2009 14:43:42 +0100
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Subject: Re: [Autoconf] new charter
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Hi Teco,

El vie, 27-02-2009 a las 18:01 +0100, Teco Boot escribió:
> Inline.
> 
> |-----Oorspronkelijk bericht-----
> |Van: Alexandru Petrescu [mailto:alexandru.petrescu@gmail.com]
> |Verzonden: vrijdag 27 februari 2009 14:24
> |Aan: Teco Boot
> |CC: 'Alexandru Petrescu'; autoconf@ietf.org
> |Onderwerp: Re: [Autoconf] new charter
> |
> |Teco Boot a écrit :
> |> Hi Alex,
> |>
> |> Let's try to be accurate:
> |>
> |> [skip]
> |> |Sorry... in the picture above the addresses are also /128.  It was an
> |> |abbreviation for me to show only 2001:db8:1::1/64 assigned to Host1.
> |> |The full notation should have been 2001:db8:1::/64 prefix and
> |> |2001:db8:1::1/128.  Would the following picture satisfy the need for
> |> |/128 addresses?:
> |>
> |> When prefix::/64 is assigned to a host, it configures a /64 address
> |and not
> |> an /128 address.
> |
> |I'm not sure I understand.
> |
> |The prefix::/64 is typically assigned to a link, not to a host.  If a
> |host is connected to that link then it configures a /128 address and a
> |/64 subnet prefix, both "128" and "64" numbers are visible in its
> |tables.
> |
> |I don't understand why the need for /128 prefixes, why isn't the above
> |/64-prefix-and-/128address not sufficient?
> 
> This is interesting. I meant generating an address in the /64 prefix.
> I don't know what is specified in RFCs. I checked behavior on Vista, 
> Linux and IOS: 
>   o Linux (debian lenny) adds a /128 prefix in the routing table, to 
>     the loopback interface, similar to what I propose in my addressing 
>     model mail. It also adds a /64 address-prefix to the Ethernet interface
>     this is a bit weird, as two interfaces has the same address configured.

	You mean the /64 for the link local addresses? this is not weird, they
have scope of a link, so there can perfectly be the same address on
different interfaces.

> 
>   o Vista assigns addresses to the Ethernet interface (in my case),
>     and adds /128 prefixes in the routing table. Vista also adds the 
>     /64 in the routing table.
>   o IOS behavior is as Vista, addresses to interfaces and /128 in 
>     routing table.
> 
> Details on Linux behavior: the /64 are on Ethernet (eth0) and the /128 
> are on loopback (lo).
> 
> # ifconfig lo | egrep 'inet6|encap'
> lo        Link encap:Local Loopback  
>           inet6 addr: ::1/128 Scope:Host
> # netstat -6rn | grep 128
> ::1/128                        ::       Un   0   1    17 lo
> 2001:db8:1:0:20c:29ff:fee3:bdf5/128 ::  Un   0   1    11 lo
> fe80::20c:29ff:fee3:bdf5/128   ::       Un   0   1     3 lo
> fe80::20c:29ff:fee3:bdff/128   ::       Un   0   1     0 lo
> 
> # ifconfig eth0 | egrep 'inet6|encap'
> eth0      Link encap:Ethernet  HWaddr 00:0c:29:e3:bd:f5  
>           inet6 addr: 2001:db8:1:0:20c:29ff:fee3:bdf5/64 Scope:Global
>           inet6 addr: fe80::20c:29ff:fee3:bdf5/64 Scope:Link
> # netstat -6rn | grep 64 
> 2001:db8:1::/64                ::       UAe  256 0    15 eth0
> fe80::/64                      ::       U    256 0     0 eth0
> fe80::/64                      ::       U    256 0     0 eth1
> 

Just a suggestion (OT to this mailing list): it's better to use the
'ip' (iproute) command (ifconfig, route and netstat are deprecated, as
far as I know since 2.4 kernels). Besides, 'ipi command is far easier to
use: 'ip -6 addr', 'ip -6 ro'

Thanks,

Carlos

> 
> Conclusion: I was wrong with my statement. Linux behaves as I mentioned, 
> other IPv6 stacks have different characteristics.
> 
> 
> 
> 
> 
> |> Routers may generate a /128 prefix-address, and advertize this in the
> |> routing domain.
> |
> |A host-based route propagated and deleted throughout a domain?  I don't
> |see the necessity of doing so.  Assuming the routers are mobile within
> |25m ranges then they wouldn't need to change their addresses, thus no
> |need to propagate host-based routes.
> 
> If the /128 is not propagated, there will be no multi-hop network. In a
> MANET, I expect nodes to run a MANET Routing protocol and forward packets.
> In ad hoc networks, one (you ?) would say nodes could be hosts or Mobile
> Routers acting as hosts. 
> 
> 
> |Do you agree we consider routers mobile only within 25m ranges?
> 
> Absolutely not. For me, 25km is a reasonable distance! Just 10^3 times the
> distance and 10^6 times the power per bit (single hop) or 10^3 times the
> power per bit if multi-hop is enabled (and 1000 intermediate nodes....).
> Just physical laws here.
> 
> 
> Teco.
> 
> 
> |Alex
> |
> |> Some mechanisms should make sure the /128 routing prefix is unique, if
> |> required. It is not required if the prefix is meant as anycast
> |address,
> |> routers may use "duplicate prefixes" if this is useful. I think
> |anycast is
> |> out-of-scope for [Autoconf], but we should be careful when specifying
> |"MUST"
> |> for prefix uniqueness. We should use "SHOULD" instead.
> |>
> |> Teco.
> |>
> |>
> |>
> |>
> 
> 
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-- 
 Carlos Jesús Bernardos Cano     http://www.netcoms.net
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