Subject: Re: [savi] AD review of draft-ietf-savi-dhcp-10

From: "Guang Yao" <[email-masked]>
Date: Wed, 8 Feb 2012 21:37:45 +0800

Hi Jari,

Thank you for the suggestion. We have made two modifications according to
your advice:

1. DNA
In section 13.6, we discuss how savi affects DNA in IPv6 and IPv4:

IPv6: NS/RS probe will not be filtered. Thus the DNAv6 process will
complete. However, the binding will not be recovered on DNAv6 messages.
Instead, it will be recovered from the DHCP snooping procedure, which is
generally slower than DNA procedure. Thus, during the gap, a number of
packets will be filtered. If BindingRecovery is enabled on the new binding
anchor, the latency can be reduced.

IPv4: ARP probe will be filtered, for the sender protocol address is not
bound on the new binding anchor. Thus the DNAv4 process will not complete.
The DHCP request sent in parallel will not be filtered for the source is all
zero. Binding will be recovered from the DHCP snooping procedure. Because
only false negative is caused, no data packet will be discarded.

Overall, DNA will not be a performance optimization with savi-dhcp. False
positive is caused in IPv6 and false negative is caused in IPv4.

2. link-local address

In section 4, 9.1, 9.2, we state that packet with link-local address will
not be discarded by savi-dhcp.

Best regards,
Guang

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf Of
Jari
> Arkko
> Sent: Wednesday, January 11, 2012 12:54 AM
> To: Guang Yao
> Cc: 'SAVI Mailing List'
> Subject: Re: [savi] AD review of draft-ietf-savi-dhcp-10
> 
> I have looked at the new draft and thought about this problem for a while.
> 
> We are making progress, but are not done yet. Or at least I have some
> questions.
> 
> Section 13.6 should indicate the performance impacts or lack thereof to
the
> overall DNA processes. For instance, I think that the use of link local
source
> addresses in NS probes in RFC 6059 means that the DNAv6 process is not
> hampered at all. But it would be good to confirm this.
> 
> On the DNAv4 side, you need to do more work. First off, there are two
possible
> impacts that SAVI DHCP could have on DNAv4. First, it could cause some
probe
> packets to be dropped. That would be generally fine as false negatives are
OK
> (but should be documented as slowing down DNAv4 acquisition process). But
if
> you were to cause false positives or prevent the host from acquiring an
address,
> that would be bad. Which is it?
> 
> I'm not sure why you say in 13.6 that the DHCP process is not mandatory in
> DNAv4. In general, the RFC was designed to provide an optimization. If the
> probing doesn't complete, the parallel DHCP process will complete
(assuming
> the network is working at all).
> 
> Section 4 and 9.1 should clearly say that link local addresses are not
checked by
> this implementations of this specification. (I think it is in fact OK to
run the SAVI
> DHCP scheme without a SAVI SLAAC solution.)
> 
> Jari
> 
> _______________________________________________
> savi mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/savi

---

From: Jari Arkko <[email-masked]>
Date: Fri, 10 Feb 2012 10:11:48 +0200

Please submit this version so that we can move the draft forward.

Jari