Subject: Re: [ppsp] [alto] ????: Re: New draft on relay usage for ALTO

From: [email-masked]
Date: Mon, 26 Oct 2009 11:43:55 +0800

Sorry to repost the mail. The former mail's title is missing.

Indeed, TIVs should be addressed in routing layer. However, solving the 
problem in routing layer may involve things like changing routing protocol 
and replacing routers, which will pay some time and high price. In 
contrary, relay is an easier solution for applications sensitive to delay, 
and is already used somewhere. 

Relay can cause layer violation. Operators may not like it. But operator's 
participating in relay selection may reduce the harm of layer violation.

Just my two cents.

On Mon, Oct 12, 2009 at 8:38 PM, Enrico Marocco
<[email-masked]> wrote:
> Sebastian Kiesel wrote:
>>> Numerous studies have reported the existence of triangle inequality
>>> violations (TIV) in the Internet delay space??for about10%-30%??. It 
has
>>> been proved to be a stable phenomenon in the Internet, and it is due
>>> to the flaw of IP routing protocol. Since it is impossible to modify
>>> the existing IP protocol, using QoS relay will be a complement to IP
>>> routing.
>>
>> Do you have more information (e.g., references to papers/studies) about
>> the true reasons for TIV? Are they due to
>>
>> 1) Non-technical, deliberate decisions of the network operators (e.g.,
>>    no business case for upgrading a line)?
>>
>> 2) Technical limitations of the IP routing protocols (BGP, OSPF, etc.)?
>>
>> 3) Technical limitations of the IP protocol itself (IPv4)?
>>
>> or ...
>>
>> Maybe also some people working for an operator can comment on this?
>
> As far as I can tell, TIVs are intrinsically related to the very nature
> of the Internet -- path asymmetry, route load balancing and so on -- and
> at the end of they could be hardly considered a problem. However,
> problem or non-problem, they entirely belong to the routing layer and
> addressing them at the application level makes to me for a perfect
> example of layer violation.
>
> --
> Ciao,
> Enrico
>
> _______________________________________________
> alto mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/alto
>
>

-- 
Sincerely yours,

Lichun Li
ZTE Corporation

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