[rrg] Fundamental objections to a host-based scalable routing solution

[Dino Farinacci]

And assumes that the data rate of the host returning traffic on the  
symmetric path is within your switchover budget. And what if traffic  
is unidirectional?

Dino

On Nov 25, 2008, at 10:34 AM, Luigi Iannone wrote:

> William Herrin wrote:
>> On Mon, Nov 24, 2008 at 11:15 PM, Robin Whittle <rw at firstpr.com.au>  
>> wrote:
>>
>>>> By contrast, a multiple-LOC multihomed host could detect the  
>>>> failure
>>>> of one of its LOCs (the one associated with the failed link)  
>>>> within a
>>>> few hundred milliseconds and switch to using just the LOCs which  
>>>> still
>>>> work. Detection is straightforward: if you're round-robining  
>>>> through
>>>> the available LOCs as you send packets, the failed LOC sets are the
>>>> ones that stop reliably returning responses.
>>>>
>>> I can't see how every multihomed host could be required to
>>> continually test reachability with extra packets, or that it would  
>>> be
>>> good to have each host sending out packets through multiple ISP  
>>> links
>>> as a means of detecting an outage.
>>>
>>
>> Who said anything about sending extra packets? The payload packets  
>> are
>> the test. The acks (or their absence) are the response to the test.
>>
>>
>
>
> This if you assume symmetric traffic (e.g., TCP) and symmetric routing
> (i.e.,  A -> B = B -> A).
> IMHO you can't make this assumption.
>
> Cheers
>
> Luigi
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