Re: [Gen-art] Gen-ART LC review of draft-ietf-mext-nemo-v4traversal-06.txt
Brian E Carpenter <brian.e.carpenter@gmail.com> Mon, 01 December 2008 20:17 UTC
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Date: Tue, 02 Dec 2008 09:17:11 +1300
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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To: Hesham Soliman <hesham@elevatemobile.com>
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Cc: draft-ietf-mext-nemo-v4traversal@tools.ietf.org, mext-chairs@tools.ietf.org, General Area Review Team <gen-art@ietf.org>, Jari Arkko <jari.arkko@piuha.net>
Subject: Re: [Gen-art] Gen-ART LC review of draft-ietf-mext-nemo-v4traversal-06.txt
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Hi Hesham, see in line. Especially on the GRE point, I think there's still an open issue. On 2008-12-01 21:50, Hesham Soliman wrote: > Hi Brian, > > Thanks for the review and apologies for the late response. I'll only respond > to comments that need further discussions or include your questions. I won't > include comments that I'll address as you requested. > >> 3.3.2. Foreign Network Supports IPv4 Only >> >> If the mobile node is in a foreign network that only supports IPv4, >> it needs to detect whether a NAT is in its communication path to the >> home agent. This is done while exchanging the binding update and >> acknowledgement messages as shown later in this document. NAT >> detection is needed for the purposes of the signaling presented in >> this specification. A mobile node SHOULD NOT assume that its IPv4 >> address is globally unique if a NAT device was not detected. > > > > Don't understand the last sentence. How, then, does the node choose to > enter the "3.3.2.1. Foreign Network Supports IPv4 Only (Public Addresses)" > logic? > > => Perhaps it was my clumsy way of saying "just because there is no NAT > between a MN and the HA, doesn't mean your address is globally unique", > which is true of course. But I'm not sure it's a useful comment. So I can > remove that. Yes, I think in this case deletion is the best clarification :-) > >> F >> >> When set, this flag indicates a request for forcing UDP >> encapsulation regardless of whether a NAT is present on the path >> between the mobile node and the home agent. > > > > In what circumstances is this set? (Same question for 4.2.2.) > > => If the MN is configured by a policy that requires it to always use UDP > encapsulation, or if it tried normal IP in IP and it didn't work. Presumably > the latter happened because the firewall didn't allow IP in IP. OK. I think it would be clearer for the reader if you add this information. > >> IPv4 Home Address >> >> The IPv4 home address that the home agent will use in the binding >> cache entry. This could be a public or private address. > > > > But if it's private, it's of no value to the mobile, which cannot send > to it. Surely the mobile (and possibly its correspondent node) needs to > know the public address of the NAT that hides the private home address? > > => This is the home address of the mobile node. It doesn't send to it. I > think you must've thought it was the home agent's address? I certainly wasn't thinking quite clearly. Of course, it's the correspondent node that can never send directly to the private home address; the correspondent node will only ever know the NATted home address. > >> 4.2.2. The NAT Detection Option > >> This option is sent from the home agent to the mobile node to >> indicate whether a NAT was in the path. This option MAY also include >> a suggested NAT binding refresh time for the mobile node. > > > > The home agent has even less chance than the mobile of guessing the NAT's > timeout. So why is this refresh time a useful addition to the protocol, > rather than just defining the mobile node's default refresh as NATKATIMEOUT? > > => It was suggested by people to allow home agent's that are usually within > the same admin domain to configure longer periods based on administrative > configuration. This is for networks like 3GPP networks where the mobile node > is usually within the same admin domain. OK, as long as there is a reason for the extra complication. > > >> 5.1. Tunelling Formats >> The following value is assigned to the Type field, other values may >> be assigned in the future: >> >> 1 GRE > > > > I'm puzzled by the choice of acronym. GRE refers to RFC2784 which has its > own encapsulation header format. > > => I know, it's the same GRE. People wanted to put GRE encapsulation in this > specification. Well in that case there needs to be a reference to RFC2784 and perhaps RFC2890. I'm quite confused, because there is nothing in the text that refers to GRE encapsulation - the only specific encapsulation mentioned is RFC2473 and RFC4213, and neither of those use GRE as far as I know. You can't use the same TLV to indicate both GRE and non-GRE encapsulations. > >> To accommodate traffic that uses Explicit Congestion Notification >> (ECN), it is RECOMMENDED that the ECN information is copied between >> the inner and outer header as defined in [RFC3168]. > > > > OK, but why not also suggest that the DSCP be copied, as defined in > RFC2983 (which is Informational)? > > => Ok, but I'll use 4213, which obsoletes 2983. Wrong! It obsoletes 2893. Very confusing... > >> 5.2. NAT Detection >> Upon receiving the binding acknowledgement with the NAT detection >> option, the mobile node sets the tunnel to the home agent to UDP >> encapsulation. Hence, all future packets to the home agent are >> tunneled in UDP and IPv4. For all tunneled IPv6 packets, the source >> address in the IPv6 header is the mobile node's IPv6 home address and >> the destination address is the correspondent node's IPv6 address. >> All tunneled IPv4 packets will contain the mobile node's IPv4 home >> address in the source address field of the inner IPv4 packet and the >> correspondent node's IPv4 address in the destination address field. > > > > Where did the correspondent node's IPv4 address come from? > > => Well, the mobile node is talking to a correspondent node. The address > could come from anywhere. This is simply an illustration of how traffic is > routed from a correspondent node to a mobile node and vice versa. OK, but I believe this is almost the only place that the correspondent node is mentioned, so it came as a bit of a surprise. > >> A mobile node MUST always tunnel binding updates in UDP when located >> in an IPv4-only network. > > > > How does the mobile know that it's in an IPv4-only network? (Also, there's > a missing verb in that sentence.) > > => Ok about the verb. The mobile node knows because it didn't receive any > IPv6 information from the router, i.e. Router advertisements. I think you should say a few words about that (i.e. that you assume that the stack provides a status indicator of some kind for this, since this is not a part of MIP6 itself). Brian _______________________________________________ Gen-art mailing list Gen-art@ietf.org https://www.ietf.org/mailman/listinfo/gen-art
- [Gen-art] Gen-ART LC review of draft-ietf-mext-ne… Brian E Carpenter
- Re: [Gen-art] Gen-ART LC review of draft-ietf-mex… Hesham Soliman
- Re: [Gen-art] Gen-ART LC review of draft-ietf-mex… Brian E Carpenter
- Re: [Gen-art] Gen-ART LC review of draft-ietf-mex… Hesham Soliman