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[mpls] 答复: [Bier] Encapsulation first nibble

Xuxiaohu <xuxiaohu@huawei.com> Tue, 17 March 2015 21:51 UTC

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From: Xuxiaohu <xuxiaohu@huawei.com>
To: "Zhaohui (Jeffrey) Zhang" <zzhang@juniper.net>, Antoni Przygienda <antoni.przygienda@ericsson.com>, "stbryant@cisco.com" <stbryant@cisco.com>, Eric Rosen <erosen@juniper.net>, BIER <bier@ietf.org>
Thread-Topic: [Bier] Encapsulation first nibble
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Date: Tue, 17 Mar 2015 21:51:21 +0000
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Subject: [mpls] 答复: [Bier] Encapsulation first nibble
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Hi Jeffrey,

> -----邮件原件-----
> 发件人: Zhaohui (Jeffrey) Zhang [mailto:zzhang@juniper.net]
> 发送时间: 2015年3月18日 1:36
> 收件人: Antoni Przygienda; Xuxiaohu; stbryant@cisco.com; Eric Rosen; BIER
> 抄送: mpls@ietf.org; sfc@ietf.org
> 主题: RE: [Bier] Encapsulation first nibble
> 
> Today those "heuristics" are typically used in very specific deployments where
> an operator knows well what kind of traffic is going through their MPLS
> infrastructure.
> 
> As Eric mentioned in the other message, a nibble value specific to BIER might
> be useful for other purpose than ECMP entropy, and if such a value is
> standardized (like value 0 and 1 that are reserved for PWs), then it helps reduce
> the clashing with random/hacky heuristics usages.

Following such logic (i.e., assign a nibble value specific to the new encapsulation header), we would have to consider how many available nibble values are there which can be used for future encapsulation headers in the same way.

Best regards,
Xiaohu

> Jeffrey
> 
> > -----Original Message-----
> > From: BIER [mailto:bier-bounces@ietf.org] On Behalf Of Antoni
> > Przygienda
> > Sent: Tuesday, March 17, 2015 1:16 PM
> > To: Xuxiaohu; stbryant@cisco.com; Eric Rosen; BIER
> > Cc: mpls@ietf.org; sfc@ietf.org
> > Subject: Re: [Bier] Encapsulation first nibble
> >
> > Not being much of an encapsulation, data plane guy myself, I wonder a
> > tad how hacky those 'heuristics' are.  Last label indicates clearly a
> > BIER header is following. For the LSRs that do not support BIER and do
> > not parse the BIER encaps there is no reason to look 'behind the label'.
> > Multiple sub-domains allow for clean separation of traffic with
> > different properties if needed and with that there is even less reason
> > for some kind of 'heuristic' DPI
> >
> > Now, given some 'heuristics' are in place no matter what value we put
> > into the nibble, sooner or later we'll collide with it no matter what
> > value we pick since such 'heuristics' basically try to parse bits
> > without understanding their context and with that can easily mistake
> > an 'eye' for an 'I' or an 'aye'.
> >
> > --- tony
> >
> >
> >
> > _______________________________________________
> > BIER mailing list
> > BIER@ietf.org
> > https://www.ietf.org/mailman/listinfo/bier

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