thanks! Jun Bi From: eric levy-abegnoli Sent: Thursday, April 12, 2012 3:47 PM To: Guang Yao Cc: [email protected] ; [email protected] Subject: Re: [savi] Last Call: <draft-ietf-savi-dhcp-12.txt> (SAVI Solution for DHCP) to Proposed Standard
Hi Guang, I realized I never acknowledged your responses. Sorry for the delay. It does clear my concerns. Thank you! Eric On 16/03/12 07:42, Guang Yao wrote: Hi, Eric Thank you for the comments. My replies are in the line. We have updated the text as the attachment. Sorry for it cannot be submitted because the submit window is closed. Best regards, Guang 2012/3/13 eric levy-abegnoli <[email protected]> Hi, here are my substantive comments Look for [eric]. Eric 7.3.1. Timer Expiration Event EVE_ENTRY_EXPIRE: The lifetime of an entry expires [eric] 2 minutes sounds very long. DHCP client timeout is 1 sec for the first message. Then multiplied by 2, etc. What is the rational behind this value, which increase the window for DoS attacks? [guang] In RFC3315, it reads: "RT for the first message transmission is based on IRT: RT = IRT + RAND*IRT RT for each subsequent message transmission is based on the previous value of RT: RT = 2*RTprev + RAND*RTprev MRT specifies an upper bound on the value of RT (disregarding the randomization added by the use of RAND). If MRT has a value of 0, there is no upper limit on the value of RT. Otherwise: if (RT > MRT) RT = MRT + RAND*MRT" Here MRT is 120s. Based on this value, the maximum retransmission time is in range of 120s(+-)12s. Thus, we think 120s is a favorable value to remove an entry. The DoS in this window is a problem, but we think the binding number limitation on each binding anchor can mitigate the damage. 8. Supplemental Binding Process [eric] This section is very unclear. The conditional SHOULD based on "vendor ability" sounds like a "MAY" to me, which is not what I remember of the WG consensus. In addition, hosts are not required to (DHCP) re-configure upon link flapping, even when they are directly attached. The text seems to indicate otherwise. In practice, in the absence of such mechanism, traffic will be blocked. [guang] We have removed the condition on "vendor ability" . Link flap is handled through keeping bindings for a period after binding anchor off-link. We have changed the text to make it clear. 8.1. Binding Recovery Process [eric] It is unclear what the address is bound to. In the normal case, the entry is created upon receiving a message (i.e. REQUEST) from the client, and the anchor is stored by that time. You should specified where the anchor comes from in this scenario, and where was it stored (given that the section specifies the binding entry creattion on LQ Reply) [guang] We have changed the text, and specified each step. Tell me if it is still unclear. 10. State Restoration [eric] Requiring non-volatile memory sounds wrong. Other techniques exists such as redundant boxes (switches) synchronizing states. I don't recall that non-volatile memory was discussed at length in the WG, especially given that it carries its own challenges: frequency for saving states, load incurred, etc) The one technique that was discussed in the WG was Binding Recovery process. One solution should be enough. [guang] There can be a large number of bindings on the savi device. If only relying on the binding recovery process, there can be a large latency. Especially, the recovery in this mechanism requires querying the DHCP server. Moreover, the storing in non-volatile memory is just recommended but not mandatory. Using redundant box can be another suggestion. We have change the MUST to MAY in text. Eric On 06/03/12 16:01, The IESG wrote: The IESG has received a request from the Source Address Validation Improvements WG (savi) to consider the following document: - 'SAVI Solution for DHCP' <draft-ietf-savi-dhcp-12.txt> as a Proposed Standard The IESG plans to make a decision in the next few weeks, and solicits final comments on this action. Please send substantive comments to the [email protected] mailing lists by 2012-03-20. Exceptionally, comments may be sent to [email protected] instead. In either case, please retain the beginning of the Subject line to allow automated sorting. Abstract This document specifies the procedure for creating bindings between a DHCPv4 [RFC2131]/DHCPv6 [RFC3315] assigned source IP address and a binding anchor [I-D.ietf-savi-framework] on SAVI (Source Address Validation Improvements) device. The bindings can be used to filter packets generated on the local link with forged source IP address. The file can be obtained via http://datatracker.ietf.org/doc/draft-ietf-savi-dhcp/ IESG discussion can be tracked via http://datatracker.ietf.org/doc/draft-ietf-savi-dhcp/ballot/ No IPR declarations have been submitted directly on this I-D. _______________________________________________ savi mailing list [email protected] https://www.ietf.org/mailman/listinfo/savi _______________________________________________ savi mailing list [email protected] https://www.ietf.org/mailman/listinfo/savi -------------------------------------------------------------------------------- _______________________________________________ savi mailing list [email protected] https://www.ietf.org/mailman/listinfo/savi
