RE: [dnsop] Re: Root Anycast (fwd)

"Joe Shen" <jshen@christmas.9966.org> Thu, 30 September 2004 17:06 UTC

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From: Joe Shen <jshen@christmas.9966.org>
To: 'Dean Anderson' <dean@av8.com>, ietf@ietf.org
Date: Thu, 30 Sep 2004 09:33:42 +0800
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Cc: dnsop@lists.uoregon.edu
Subject: RE: [dnsop] Re: Root Anycast (fwd)
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Would you please give more about  the problem of  anycast with root
server ? 

To my understanding, Per-Packet Load Balancing  works only in situation
all  DNS servers installed
behind the same router, and it  CAN NOT guarantee sequencing of TCP
packets.  

The first problem of PPLB  is ,  it could not be implemented  for a
server farm which distributes across 
internet, and  the only thing it does is  replacing traditional  load
balancer  with router. 

I don't know whether there is some research in  "how many packets does
one DNS request cost " and "how
many TCP traffic occupies in DNS traffic".  If  most of DNS request cost
more than one UDP packets, out-of-sequence 
may be a problem. Also , if TCP occupies more than 10% of traffic it
will also be a problem. 

The third,  ECMP in current  DNS server farm guarantees both per-packet
load balancing in UDP traffic and per-flow distribution
in TCP traffic.  Considering distributing DNS server across multiple AS,
I think the advange is obvious than PPLB.



Joe Shen


ps.  where can I find detailed information on Root server GTLD server
configuration  ( hardware , software, and network infrastructure)?
        I just know they use anycast but how they choose system
platform?


-----Original Message-----
From: owner-dnsop@lists.uoregon.edu
[mailto:owner-dnsop@lists.uoregon.edu] On Behalf Of Dean Anderson
Sent: Thursday, September 30, 2004 5:41 AM
To: ietf@ietf.org
Cc: dnsop@lists.uoregon.edu
Subject: [dnsop] Re: Root Anycast (fwd)


Some time back we were talking about anycast being a bad thing on DNS
Root servers. It was suggested by that conversations typically take only
one path as a result of CEF-like caching.  I noted that providers were
working on per packet load balancing. Well, here it is, in the "major
vendor":

Per-Packet Load Balancing
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft
/120limit/120s/120s21/pplb.htm

So, it seems that we need to review whether the use of anycast on the
root nameservers is a good idea. I suggest that we ignore for the
momeent anyway the question of whether the deployment of anycast was
done with adequate technical analysis, discussion, and approval, and
just consider whether we should continue doing it.  However, the Root
server operation and oversight issues are very important should also be
discussed, too, but probably by different forums.

		--Dean

---------- Forwarded message ----------
Date: Tue, 18 May 2004 19:03:52 -0400 (EDT)
From: Dean Anderson <dean@av8.com>
To: Paul Vixie <vixie@vix.com>
Cc: ietf@ietf.org
Subject: Re: Root Anycast

On 18 May 2004, Paul Vixie wrote:

> Careful design by whom?  Organic compared to what?  I assure you that 
> f-root has grown by careful design.  It's only organic in that we go 
> where we're invited rather than having a gigantic budget that could be

> used as a leash.

Do you mean "Careful Design" like the non-standard changes in Bind 9
AXFR and IXFR?  I don't think we can take too much of that sort of thing
in the operation of the root servers before we have serious problems.

Unilateral action is not a good thing. There is no point in having an
IETF (Remember the "Internet __Engineering__ Task Force" in IETF) if you
just implement whatever you think OK at the moment (AXFR mods, IXFR
mods, Anycast, and probably more that we just don't yet know about)

		--Dean


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