Re: [mpls] draft-fang-mpls-label-forwarding-no-swap - how much does it really save?

Xuxiaohu <xuxiaohu@huawei.com> Wed, 29 July 2015 03:07 UTC

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From: Xuxiaohu <xuxiaohu@huawei.com>
To: Andrew Qu <andrew.qu@mediatek.com>, "stbryant@cisco.com" <stbryant@cisco.com>, Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>, Robert Raszuk <robert@raszuk.net>, Shahram Davari <davari@broadcom.com>
Thread-Topic: [mpls] draft-fang-mpls-label-forwarding-no-swap - how much does it really save?
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Date: Wed, 29 Jul 2015 03:06:45 +0000
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Subject: Re: [mpls] draft-fang-mpls-label-forwarding-no-swap - how much does it really save?
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> So the question really boils down to that do we need global label?
> 
> I believe that is the key thing here.  May be we can put swap/no-swap aside for
> the moment.

Concur.

Best regards,
Xiaohu

> Thanks,
> 
> Andrew
> 
> 
> -----Original Message-----
> From: Stewart Bryant [mailto:stbryant@cisco.com]
> Sent: Tuesday, July 28, 2015 4:03 AM
> To: Andrew Qu; Alexander Vainshtein; Robert Raszuk; Shahram Davari
> Cc: mpls@ietf.org
> Subject: Re: [mpls] draft-fang-mpls-label-forwarding-no-swap - how much does
> it really save?
> 
> > Adding "NO_SWAP" for new/future generation DEVICE does NOT break
> > backward capability.
> >
> Andrew
> 
> Existing devices should be assumed to have non-aligned label spaces.
> (there is much empirical evidence to support this position)
> 
> So if you have a no-swap only device between two existing devices you cannot
> be sure that you can build an LSP.
> 
> A backwards compatible device would therefore need to support swap.
> 
> Once you support swap then no-swap become an optimization.
> 
> - Stewart
> 
> 
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