Re: Last Call: draft-ietf-6lowpan-format (Transmission of IPv6 Packets over IEEE 802.15.4 Networks) to Proposed Standard
Pekka Savola <pekkas@netcore.fi> Sun, 04 March 2007 19:58 UTC
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Date: Sun, 04 Mar 2007 21:57:54 +0200
From: Pekka Savola <pekkas@netcore.fi>
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Subject: Re: Last Call: draft-ietf-6lowpan-format (Transmission of IPv6 Packets over IEEE 802.15.4 Networks) to Proposed Standard
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On Thu, 15 Feb 2007, The IESG wrote: > The IESG has received a request from the IPv6 over Low power WPAN WG > (6lowpan) to consider the following document: > > - 'Transmission of IPv6 Packets over IEEE 802.15.4 Networks ' > <draft-ietf-6lowpan-format-10.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 > ietf@ietf.org mailing lists by 2007-03-01. Exceptionally, > comments may be sent to iesg@ietf.org instead. In either case, please > retain the beginning of the Subject line to allow automated sorting. > > The file can be obtained via > http://www.ietf.org/internet-drafts/draft-ietf-6lowpan-format-10.txt Sorry for slightly missing the LC deadline. Some comments below. A couple of meta-points: - the specification for Mesh type networks seems incomplete, and the draft recognizes it as such. It's not clear to me what's the benefit of including that operational mode in the first place given that it's not likely to interoperate. - are all nodes expected to support both 'short address' and long address addressing types, i.e., having both on the same link will interoperate? There are no requirements about this but those may be in the IEEE specification. I assume supporting both is required. - Security Considerations could mention RFC3041 and possibly short-from addresses in the first paragraph. - There appears to be no mandatory-to-implement security model for mesh-type networks. (Well, given that there isn't even a good specification of how mesh-type network would work, it's no surprise..) A few specific comments: If a link fragment is received that overlaps another fragment as identified above and differs in either the size or datagram_offset of the overlapped fragment, the fragment(s) already accumulated in the reassembly buffer SHALL be discarded. ==> this is similar to IP reassembly, but suffers from overlapping fragment attacks discussed in RFC 1858. Given the more limited attack vector (the same IP link), this might be acceptable. Has this attack been discussed? Were alternatives (e.g., 'discard new' instead of 'replace old') considered? 6. Stateless Address Autoconfiguration ==> no mention is made regarding IPv6 privacy addressing (RFC 3041, or a bis draft). Is it applicable as well? The last sentence at the end of section 8 seems to suggest so. Thus, the following common IPv6 header values may be compressed from the onset: Version is IPv6; both IPv6 source and destination addresses are link local; the IPv6 interface identifiers (bottom 64 bits) for the source or destination addresses can be inferred from the layer two source and destination addresses (of course, this is only possible for interface identifiers derived from an underlying 802.15.4 MAC address); ==> The address compression part is not clear. Are you saying that only link-local addresses can be compressed using this methodology? Do you envision that applications run in a PAN use link-local or some other addresses? I'd have major architectural objections to using link-locals in applications due to their ambiguity and difficulties with zone index handling in the apps. (On the next page with actual technical details of compression it becomes clearer how compression can be used in various scenarios. Maybe the list above and partial details therein may be unnecessary.) Range 2, 100xxxxxxxxxxxxx: Bits 0,1 and 2 SHALL follow this pattern if the 16-bit address is a multicast address (see Section 9). This leaves 13 bits for the actual multicast address. ==> if a multicast-based short address were to be used as a source address, behaviour would be unspecified. Is that OK? More generally, as the type of the address is deep inside the 64-bit IID, it's not clear how well nodes are able to recognize it in any case. Wouldn't it be perfectly legitimate for a node to manually configure an interface identifier which would be indistinguishable from a short address EID? Is it necessary to be able to tell short-address EIDs and other EIDs apart somehow? editorial --------- ==> the same comment wrt 'personal' in LoWPAN as for the goals draft applies here. It's not obvious to me what's 'personal' in this specification or technology. Abstract This document describes the frame format for transmission of IPv6 packets and the method of forming IPv6 link-local addresses and statelessly autoconfigured addresses on IEEE 802.15.4 networks. Additional specifications include a simple header compression scheme using shared context and provisions for packet delivery in IEEE 802.15.4 meshes. ==> 'additional specifications' probably refers to other documents, yet section 10 appears to define at least something related to header compression. Is the Abstract up-to-date? | 01 111111 | ESC - Additional Dispatch byte follows | +----------+-----------------------------------------------+ ==> off-by-two at the bottom of the table.. datagram_size: This 11 bit field encodes the size of the entire IP payload datagram. ==> .. 'in octets' ? You don't specify the unit.. Next Header (bits 5 and 6): 00: not compressed, full 8 bits are sent 01: UDP 10: ICMP 11: TCP ==> s/ICMP/ICMPv6/ -- you probably refer to protocol=58 instead of protocol=1 ? (the same later in the section) 15.2. Informative References [I-D.ietf-ipngwg-icmp-v3] [I-D.ietf-ipv6-node-requirements] ==> these have been published in RFCs (but neither is actually used in the body of the text, so could be fixed and added or removed completely). -- Pekka Savola "You each name yourselves king, yet the Netcore Oy kingdom bleeds." Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings _______________________________________________ Ietf mailing list Ietf@ietf.org https://www1.ietf.org/mailman/listinfo/ietf
- Re: Last Call: draft-ietf-6lowpan-format (Transmiā¦ Pekka Savola