> -----邮件原件-----
> 发件人: Xu Xiaohu [mailto:[email protected]]
> 发送时间: 2010年1月19日 20:59
> 收件人: 'Rémi Després'
> 抄送: 'Mark Townsley'; '[email protected]'
> 主题: re: routing loop issue//re: [Softwires] Please review 6rd
>
>
>
> > -----邮件原件-----
> > 发件人: Rémi Després [mailto:[email protected]]
> > 发送时间: 2010年1月19日 19:06
> > 收件人: Xu Xiaohu
> > 抄送: 'Mark Townsley'; [email protected]
> > 主题: Re: routing loop issue//re: [Softwires] Please review 6rd
> >
> >
> > Le 19 janv. 2010 à 11:01, Xu Xiaohu a écrit :
> >
> > >>>
> > >>> By the way, would it be better for preventing the routing loops if
there
> > >>> were some well-known bits in the 6rd prefix?
> > >>
> > >> This would IMHO add complexity, unnecessarily since routing loops
> > >> are avoided
> > >> with the described ingoing and outgoing filters in the BRs.
> > >
> > > Sorry for late response. Will this approach of blindly filtering any
packet
> > > sourced from the BRs drop the normal tunneled packets mistakenly?
> >
> >
> > The draft says:
> > To avoid forwarding loops via other internal relays, the BR should
> > employ outgoing and incoming IPv4 packets filters, filtering out all
> > known relay addresses for internal 6rd BRs, ISATAP routers or 6to4
> > relays, including the well known anycast address space for 6to4.
> >
> > In my understanding, this will not filter any packet that should be
forwarded.
>
> If there is a softwire tunnel between two BRs, wouldn't the packet
tunneled
> in the softwire be filtered blindly?
+------------------------+
| |
| |
| IPv6 Internet |
| |
+------+----------+------+
| |
| |
+--+--+ +--+--+
+---+6rd-A+-----+6rd-B+--+
| +-----+ +-----+ |
| |
| IPv4 ISP |
| +-------+ |
+-------+ CPE-1 +--------+
+---+---+
|
+-----+-----+
| |
| IPv6 Site |
+-----------+
In the above scenario, two 6rd BRs are configured with the same address for
anycast service. Assuming the nearest 6rd BR for the CPE is 6rd-A, all IPv6
packets from the IPv6 site and destined to the IPv6 internet will be
tunneled towards 6rd-A by the CPE. Once 6rd-A lost connections to the IPv6
Internet, some failover mechanism should be used to direct these packets
towards 6rd-B. One possible solution is: 6rd-A withdraws the route to the
IPv6 Internet, which was advertised in IPv4 ISP network previously, as soon
as its connection to the IPv6 Internet is lost. Another solution is:
establish a softwire tunnel between the two 6rd BRs for failover route. With
the latter solution, some normal packets tunneled in the softwire during
failover will be filtered mistakenly.
Xiaohu
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