On Dec 22, 2006, at 1:05 AM, Yue Wang wrote:
On 12/22/06, Acee Lindem <[EMAIL PROTECTED]> wrote:
Hi Yue,
On Dec 21, 2006, at 9:08 PM, Yue Wang wrote:
> Dear Acee and All,
>
> The last thing to raise your attention (see below).
>
> Thanks a lot for your advice and discussion. Look forward to the
> future anycast standard in OSPFv3.
>
<pruned>
>
>
>> > 2) Anycast Route Calculation
>> >
>> > I agree that the anycast route calculation is similar to the
>> unicast
>> > case. But there is a bug noticed in Case 1 in Sec 3.5.1 if we
>> consider
>> > anycast the same as unicast. The last comer (anycast server)
will
>> > replace the previous route entries (in the logic of unicast).
As a
>> > result, there is ONLY ONE route entry for a given anycast
address.
>> > This means all client requests will go to the same anycast
server.
>> Not in any of my implementations - if you calculate ECMP
>> (Equal Cost Multipath) routes, most implementations will
>> distribute flows (based on source/dest or some longer tuple
>> including other flow qualifiers) across the equal cost routes.
>>
>
> Note that anycast routes are not necessarily equal cost.
> Suppose there are 2 anycast routes coming into a OSPF network in
> sequence: the first is 1 hop, the second is 2 hop. As a result,
ONLY
> the 2-hop route stays in the network, if we treat anycast as
unicast.
Independent of address type (unicast or anycast), you take the
shortest path. What are you proposing for anycast that deviates from
this
premise?
I simply maintained a route list for each anycast address so that the
1-hop route will not be flushed by the 2-hop route in the above
example.
Assuming the 1-hop route is lower cost, this shouldn't be necessary.
Look at section 3.8.1 in RFC 2740. Every router advertising anycast
addresses simply advertises the closest anycast address. How this is
accomplished is an implementation specific matter and depends how
the anycast addresses are discovered - is that what you're
trying to accomplish with your route lists?
Thanks,
Acee
Thanks,
Acee
>
>
> --
> regards,
> wang yue
>
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--
regards,
wang yue
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