Hello Thomas: I’ll create a ticket for this. To answer your question below:
The "RPL Packet Information" is defined in RFC 6550, because RPL does not mandate that it is placed in a HbH header as a RPL option or elsewhere. As it goes, we are expressly compressing the RPL option form, so I agree it would have made sense to use that term as well. Quoting RPL: “ RPL also expects an external mechanism to access and transport some control information, referred to as the "RPL Packet Information", in data packets. The RPL Packet Information is defined in Section 11.2<http://tools.ietf.org/html/rfc6550#section-11.2> and enables the association of a data packet with a RPL Instance and the validation of RPL routing states. The RPL option [RFC6553<http://tools.ietf.org/html/rfc6553>] is an example of such mechanism. The mechanism is required for all packets except when strict source routing is used (that is for packets going Downward in Non-Storing mode as detailed further in Section 9<http://tools.ietf.org/html/rfc6550#section-9>), which by nature prevents endless loops and alleviates the need for the RPL Packet Information. Future companion specifications may propose alternate ways to carry the RPL Packet Information in the IPv6 packets and may extend the RPL Packet Information to support additional features. “ Take care ; Pascal From: Thomas Watteyne [mailto:[email protected]] Sent: lundi 8 février 2016 14:20 To: Pascal Thubert (pthubert) <[email protected]> Cc: Tengfei Chang <[email protected]>; Simon Duquennoy <[email protected]>; [email protected]; [email protected] Subject: Re: [6lo] Format inside of an RPL domain [resending from the right e-mail address] On Mon, Feb 8, 2016 at 2:16 PM, Thomas Watteyne <[email protected]<mailto:[email protected]>> wrote: Pascal, I hope my comments don't come too late. Please find below some edits of your suggested text. My biggest comment is about naming, as I think we are using "nicknames" for things, which makes things very hard to follow. Thomas ## DODAG Root Address {#impl-comp-ref} With this specification, an optimal compression TW> I would drop the word "optimal", which implies you can prove it. Replace by "efficient"? of IP-in-IP encapsulation can be achieved if an endpoint of the packet is the root of the RPL DODAG associated to the Instance TW> please make sure that you use the capital "I" on purpose that is used to forward the packet, and the root address is known implicitly as opposed to signaled explicitly in the data packets. With RPL {{RFC6550}}, the address of TW> add "the" DODAG root is known from the DODAGID field of the DIO messages. For a Global Instance, the RPLInstanceID that is present in the RPI TW> where does the term RPI come from? According to RFC6553, the full name is "RPL Option", no? is enough information to identify the DODAG that this node participates to and its associated root. But for a Local Instance, the address of the root MUST be explicit, either in some device configuration or signaled in the packet, as the source or the destination address, respectively. When implicit, the address of the DODAG root MUST be determined as follows: If the whole network is a single DODAG then the root can be well-known and does not need to be signaled in the packets. But TW> "if" missing? RPL does not expose that property and it can only be known by a configuration applied to all nodes. Else, the router that encapsulates the packet and compresses it with this specification MUST also place an RPI in the packet as prescribed by {{RFC6550}} to enable the identification of the DODAG. The RPI must be present even in the case when the router also places an RH3 header in the packet. It is expected that the RPL implementation provides an abstract context table, indexed by Global RPLInstanceID, that provides the address of the root of the DODAG that this nodes participates to for that particular Instance. ## Compression Reference {#sig-comp-ref} In order to optimize the compression of IP addresses present in the RH3 headers, this specification requires that the 6LoWPAN layer identifies an address that is used as reference for the compression. With this specification, the Compression Reference for addresses found in an RH3 header is the source of the IPv6 packet. With RPL {{RFC6550}}, an RH3 > In the same vain as my comment about RPI, we should really force ourselves to > use the same terminology, or else it gets really really confusing. > I understand that RH3 stands for the-Routing-header-with-IPv6-routing-type-3, > but according to RFC6554, this is called "RPL Source Route Header". Let's > please use that name... header may only be present in Non-Storing mode, and it may only be placed in the packet by the root of the DODAG, which must be the source of the resulting IPv6 packet {{RFC2460}}. In this case, the address used as Compression Reference is that the address of the root, and it can be implicit when the address of the root is. The Compression Reference MUST be determined as follows: The reference address may be obtained by configuration. The configuration may indicate either the address in full, or the identifier of a 6LoWPAN Context that carries the address {{RFC6775}}, for instance one of the 16 Context Identifiers used in LOWPAN-IPHC {{RFC6282}}. Else, and if there is no IP-in-IP encapsulation, the source address in the IPv6 header that is compressed with LOWPAN-IPHC is the reference for the compression. Else, and if the IP-in-IP compression specified in this document is used and the Encapsulator Address is provided, then the Encapsulator Address is the reference. (note that this means that the specification does not expect IP-in-IP-in-IP and does not enforce any order in 6LoRH ... should it???). On Wed, Jan 20, 2016 at 4:14 PM, Pascal Thubert (pthubert) <[email protected]<mailto:[email protected]>> wrote: Hello Tengfei and Simon (and all): I’ll need some more help from you. I’m in the process of refining the text that indicates how the root address is obtained and how to compute the Compression Reference for the RH3. I came up with the following, which indicates that the source of the packet (which should always be the root for now but who knows) is the reference for RH3 compression. Is that what we want? Is it clear enough? ## DODAG Root Address {#impl-comp-ref} With this specification, an optimal compression of IP-in-IP encapsulation can be achieved if an endpoint of the packet is the root of the RPL DODAG associated to the Instance that is used to forward the packet, and the root address is known implicitly as opposed to signaled explicitly in the data packets. With RPL {{RFC6550}}, the address of DODAG root is known from the DODAGID field of the DIO messages. For a Global Instance, the RPLInstanceID that is present in the RPI is enough information to identify the DODAG that this node participates to and its associated root. But for a Local Instance, the address of the root MUST be explicit, either in some device configuration or signaled in the packet, as the source or the destination address, respectively. When implicit, the address of the DODAG root MUST be determined as follows: If the whole network is a single DODAG then the root can be well-known and does not need to be signaled in the packets. But RPL does not expose that property and it can only be known by a configuration applied to all nodes. Else, the router that encapsulates the packet and compresses it with this specification MUST also place an RPI in the packet as prescribed by {{RFC6550}} to enable the identification of the DODAG. The RPI must be present even in the case when the router also places an RH3 header in the packet. It is expected that the RPL implementation provides an abstract context table, indexed by Global RPLInstanceID, that provides the address of the root of the DODAG that this nodes participates to for that particular Instance. ## Compression Reference {#sig-comp-ref} In order to optimize the compression of IP addresses present in the RH3 headers, this specification requires that the 6LoWPAN layer identifies an address that is used as reference for the compression. With this specification, the Compression Reference for addresses found in an RH3 header is the source of the IPv6 packet. With RPL {{RFC6550}}, an RH3 header may only be present in Non-Storing mode, and it may only be placed in the packet by the root of the DODAG, which must be the source of the resulting IPv6 packet {{RFC2460}}. In this case, the address used as Compression Reference is that the address of the root, and it can be implicit when the address of the root is. The Compression Reference MUST be determined as follows: The reference address may be obtained by configuration. The configuration may indicate either the address in full, or the identifier of a 6LoWPAN Context that carries the address {{RFC6775}}, for instance one of the 16 Context Identifiers used in LOWPAN-IPHC {{RFC6282}}. Else, and if there is no IP-in-IP encapsulation, the source address in the IPv6 header that is compressed with LOWPAN-IPHC is the reference for the compression. Else, and if the IP-in-IP compression specified in this document is used and the Encapsulator Address is provided, then the Encapsulator Address is the reference. (note that this means that the specification does not expect IP-in-IP-in-IP and does not enforce any order in 6LoRH ... should it???). Cheers, Pascal From: Tengfei Chang [mailto:[email protected]<mailto:[email protected]>] Sent: lundi 18 janvier 2016 14:26 To: Pascal Thubert (pthubert) <[email protected]<mailto:[email protected]>> Cc: [email protected]<mailto:[email protected]>; [email protected]<mailto:[email protected]> Subject: Re: [6lo] Format inside of an RPL domain I agree with this format! +1 Tengfei On Mon, Jan 18, 2016 at 9:41 AM, Pascal Thubert (pthubert) <[email protected]<mailto:[email protected]>> wrote: Dear TengFei: I agree that the draft is lacking description when there is no IP in IP. I’ll create a ticket. When there is no IP in IP present in the 6LoRH, then the headers compressed by 6LoRH are considered placed right after the IP header compressed by IPHC, and considered as compressed. It results that the NH bit in the IPHC really indicates how the compression is done for the header that is after the headers compressed by 6LoRH. For an ICMP message I’d think that you’ll be using: +- ... -+- ... -+-+-+- ... -+-+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+... |11110001| RPI | NH = 0 | NH = 58 | ICMP message |Page 1 | 6LoRH | 6LOWPAN-IPHC | (ICMP) | (no compression) +- ... -+- ... +-+-+-+- ... -+-+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+... <- RFC 6282 -> No RPL artifact Does that make sense? Pascal From: 6lo [mailto:[email protected]<mailto:[email protected]>] On Behalf Of Tengfei Chang Sent: lundi 18 janvier 2016 09:18 To: [email protected]<mailto:[email protected]> Subject: [6lo] Format inside of an RPL domain Dear All, Currently I have a question about the format of packet inside of an RPL domain when using 6LoRH. For example when ping a mote inside an RPL domain, will the format of echo request and reply look like this? PAGE DISPATCH (page 1) + IPHC + 6LoRH RH3 + ICMPv6 PAGE DISPATCH (page 1) + IPHC + 6LoRH RPI + ICMPv6 If so, there is no next header field in 6LoRH to indicate the following field is ICMP. What's the right format for this case? Thanks a lot! Tengfei _______________________________________________ 6lo mailing list [email protected]<mailto:[email protected]> https://www.ietf.org/mailman/listinfo/6lo
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