Re: [v6ops] [tcpm] Flow Label Load Balancing

Fernando Gont <fgont@si6networks.com> Fri, 04 December 2020 23:35 UTC

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To: Tom Herbert <tom@herbertland.com>, Brian E Carpenter <brian.e.carpenter@gmail.com>
Cc: Erik Kline <ek.ietf@gmail.com>, IPv6 Operations <v6ops@ietf.org>, tcpm <tcpm@ietf.org>, Fernando Gont <fernando@gont.com.ar>
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From: Fernando Gont <fgont@si6networks.com>
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Date: Thu, 3 Dec 2020 19:41:33 -0300
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Subject: Re: [v6ops] [tcpm] Flow Label Load Balancing
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Tom,

On 3/12/20 17:38, Tom Herbert wrote:
> On Thu, Dec 3, 2020 at 1:17 PM Brian E Carpenter
> <brian.e.carpenter@gmail.com> wrote:
>>
>> On 04-Dec-20 06:30, Tom Herbert wrote:
>>> On Thu, Dec 3, 2020 at 8:43 AM Erik Kline <ek.ietf@gmail.com> wrote:
[....]
>>
>> But that doesn't help with server load balancing. For ECMP/LAG in a
>> transit network, the DA alone doesn't help either, if a particular
>> destination is prone to very heavy flows for some reason.
> 
> Brian,
> 
> Specifically, that is a problem for a host that uses a _single_ IPv6
> address for all its connections. 

That that's the vast majority of current hosts - if not all.


> What I am suggesting is to give hosts
> many addresses, which we already do anyway like when mobile devices
> and data center servers are assigned /64s. If a host then randomly
> chooses an address from that block for each connection it creates
> thenl the address 2-tuple contains all the entropy needed for purposes
> of load balancing, ECMP, etc. is contained in the source address.
> Addresses are guaranteed to be present and plaintext in each packet so
> no DPI required, they're as stable as any flow identifying information
> in a packet can be and they offer much more entropy than sixteen bits
> of port number of twenty bit flow label.

Agreed. Although that move is not-trivial: e.g. if you move from shared 
link to /64 per hosts, then stuff like mDNS breaks.

There's also an API to be specifiied.

P.S.: And, in the process, we have kind of burned 64-bits of the 128-bit 
IPv6 addresses, too...


Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492