Hi Ben, I replied inline:
On Tue, Mar 24, 2020 at 8:27 PM Benjamin Kaduk <ka...@mit.edu> wrote: > Hi Tengfei, > > Also inline. > > On Tue, Mar 24, 2020 at 12:22:02PM +0100, Tengfei Chang wrote: > > Hi Benjamin, > > I replied inline starting with '>' > > Thanks so much those detailed comments! > > On Wed, Mar 11, 2020 at 6:55 PM Benjamin Kaduk via Datatracker > > <nore...@ietf.org> wrote: > > > > Benjamin Kaduk has entered the following ballot position for > > draft-ietf-6tisch-msf-12: Discuss > > > > When responding, please keep the subject line intact and reply to > all > > email addresses included in the To and CC lines. (Feel free to cut > this > > introductory paragraph, however.) > > > > Please refer to > > https://www.ietf.org/iesg/statement/discuss-criteria.html > > for more information about IESG DISCUSS and COMMENT positions. > > > > The document, along with other ballot positions, can be found here: > > https://datatracker.ietf.org/doc/draft-ietf-6tisch-msf/ > > > > > ---------------------------------------------------------------------- > > DISCUSS: > > > ---------------------------------------------------------------------- > > > > I'm concerned that the scheduling function for autonomous cells can > > cause an infinite loop in the case of hash collision -- Section 3 > > specifies that AutoTxCell always takes precedence over AutoRxCell, > but > > if those two cells collide, the corresponding cells on the peer in > > question will also collide. If both peers try to send at the same > time > > and the hashes collide, they will both attempt to transmit > indefinitely > > and never be received. > > > > > > >. Notice that the AutoTxCell is a shared cell, where the back-off > > mechanism is applied. > > > In case there is a collision on that cell, a back-off with different > > exponent will be used on each side. > > > The cell will be used AutoTxCell on each side at different timing. > > Ah, it seems I was misinterpreting "take precedence over" to apply to the > entire local scheduling, not merely the case when independent tx and rx > scheduling land on the same cell. Thanks for clarifying here; is there > anything useful to say in the document about how even if there is a > collision in the assigned slot there's still a Tx backoff, so the cell is > usable for Rx some of the time? > * RESPONSE: * We could add the following sentence right after the hashing collision statement: Notice AutoTxCell is a shared type cell which applies back off mechanism. When the AutoTxCell and AutoRxCell are collided, AutoTxCell takes precedence if there is a packet to transmit. In case in a back-off period, AutoRxCell is used. > > There seems to be some "passing the buck" going on with respect to > > rate-limiting unauthenticated (join) traffic: > > draft-ietf-6tisch-minimal-security (Section 6.1.1) says that the SF > > "SHOULD NOT allocate additional cells as a result of traffic with > code > > point AF43"; this document is implementing a SF, and yet we try to > avoid > > the issue, saying that "[t]he at IPv6 layer SHOULD ensure that this > join > > traffic is rate-limited before it is passed to 6top sublayer where > MSF > > can observe it". I think we need a clear and consistent story about > > where this rate-limiting is supposed to happen. > > > > > Thanks for the comments! This has been discussed in some previous > > revision of MSF. > > > It is not "passing the buck" but a decision based on the scheduling > > function and security context. > > > In the point of avoiding layer violation, the upper layer > information > > suppose NOT see-able for linker layer where 6P and MSF are. > > If we assume strict layiner so that IP information is not visible to the > link layer where the scheduling function lives, then isn't that a flaw in > draft-ietf-6tisch-minimal-security to say that the scheduling function > should do [something relying on IP-layer information]? > > > > But regarding to security, it seems it is not avoidable. > > > IMO, the scheduling function is aiming to provide algorithm to > > add/remove cell according to traffic. > > > The traffic could contains unauthenticated join request from both > > normal devices and malicious devices. > > > The function does NOT have enough information to differentiate them. > > > We are assuming some other entity out side of MSF needs to resolve > this > > issue. > > Nonetheless, we're currently not fulfilling a requirement that a SF should > meet. If that requirement is unattainable, the requirement should be > modified or removed; if not, we should attain the requirement. > > > >> If assuming the security info in the Ipv6 header is passed to MSF, > we > > could abandon rate-limiting approach and simply jumping over a slot > if the > > AF43 packet is sent on that slot. > > > Hence the adapting traffic never happens to traffic marked as AF43.. > > > > > ---------------------------------------------------------------------- > > COMMENT: > > > ---------------------------------------------------------------------- > > > > I support Roman's Discuss -- we need more information for this to > be a > > useful reference; even what seem to be the official DASFAA 1997 > > proceedings (https://dblp.org/db/conf/dasfaa/dasfaa97) do not have > an > > associated document). > > > > Basing various scheduling aspects on (a hash of) the EUI64 ties > > functionality to a persistent identifier for a device. How > significant > > a disruption would be incurred if a device periodically changes its > > presented EUI64 for anonymization purposes? > > > > > I assume you are saying a malicious device? > > > There is no doubt this will influence the performance of joining > process > > for normal devices. > > > But normal devices still have a chance to join. > > > the join proxy won't be affect as well since the cell will be > removed > > right after the packet is sent out. > > I was thinking a non-malicious device, just one that (for example) changes > its physical location frequently, and wants to change its EUI64 when it > does so, to avoid that location being tracked and correlated over time. > That said, your answer still seems to answer my question, and since normal > devices will still have a chance to join, it seems like we probably do not > need to add text to discuss this situation. > *RESPONSE:* Great! > > > There seems to be a general pattern of "if you don't have a > > 6P-negotiated Tx cell, install and AutoTxCell to send your one > message > > and then remove it after sending"; I wonder if it would be easier > on the > > reader to consolidate this as a general principle and not repeat the > > details every time it occurs. > > > > > Yes, this is the feature of autonomous cell. Not sure if it would > > easier to understand state just one time. > > > There is little different for each adding/removing, e.g which node > to do > > so, parent/JP? > > > I personally feel it's clear to repeat this every time, with > various > > type of node, so highlighting the difference. > > Okay. Thank you for considering the idea. > > > Requirements Language > > > > "NOT RECOMMENDED" is not in the RFC2119 boilerplate (but is a BCP 14 > > keyword). > > > > > Thanks for pointing out. It will be removed in next revision. > > > We also updated the RFC to RFC8174 instead of RFC2119. > > Oops, I think my comment was unclear. > RFC 8174 has a paragraph in it that you should copy/paste into your > document to replace this one. ("NOT RECOMMENDED" is included in that > paragraph in RFC 8174.) > > Also, you should cite both RFC 2119 and RFC 8174, not just RFC 8174 -- BCP > 14 comprises both of them together. > > * RESPONSE: * Thanks for clarifying! Will use the paragraph from RFC 1874.. > > Section 1 > > > > the 6 steps described in Section 4. The end state of the join > > process is that the node is synchronized to the network, has > mutually > > authenticated to the network, has identified a routing parent, > and > > > > nit(?): I guess maybe "mutually authenticated with" is more correct > for > > the bidirectional operation. > > > > > will update in next revision. > > > > It does so for 3 reasons: to match the link-layer resources to > the > > traffic, to handle changing parent, to handle a schedule > collision. > > > > nit: end the list with "or" (or "and"?). > > > > > will update in next revision. > > > > MSF works closely with RPL, specifically the routing parent > defined > > in [RFC6550]. This specification only describes how MSF works > with > > one routing parent, which is phrased as "selected parent". The > > > > nit: I suggest '''one routing parent; this parent is referred to as > the > > "selected parent"'''. > > > > > will update in next revision. > > > > activity of MSF towards to single routing parent is called as a > "MSF > > > > nit: "towards the" > > > > > will update in next revision. > > > > * We added sections on the interface to the minimal 6TiSCH > > configuration (Section 2), the use of the SIGNAL command > > (Section 6), the MSF constants (Section 14), the MSF > statistics > > (Section 15). > > > > nit: end the list with "and". > > > > > will update in next revision. > > > > Section 2 > > > > In a TSCH network, time is sliced up into time slots. The time > slots > > are grouped as one of more slotframes which repeat over time. > The > > > > nit(?): should this be "one or more"? > > > > > it should be 'one or multiple slotframes". Will update in next > revision > > > > channel) is indicated as a cell of TSCH schedule. MSF is one of > the > > policies defining how to manage the TSCH schedule. > > > > nit: if there is only one such policy active at a given time for a > given > > network, I suggest "MSF is a policy for managing the TCSH schedule". > > (If multiple policies are active simultaneously, no change is > needed.) > > > > > As indicated in RFC8480: A node MAY implement multiple SFs and run > them > > at the same time. > > > so MSF is one of the policies defining how to manage the TSCH > schedule. > > Thank you for the reference, and sorry for missing it. > > > MSF uses the minimal cell for broadcast frames such as Enhanced > > Beacons (EBs) [IEEE802154] and broadcast DODAG Information > Objects > > (DIOs) [RFC6550]. Cells scheduled by MSF are meant to be used > only > > for unicast frames. > > > > If this paragraph was moved before the previous paragraph, then EB > and > > DIO would be defined before their first usage. > > > > > Maybe I understand it wrong. Do you mean you prefer to move this > > paragraph before the previous one? > > > The EB and DIO are defined in the references, not sure we still need > > define them in MSF. > > That is my preference, but I defer to your preference where it differs from > mine. > > > bandwidth of minimal cell. One of the algorithm met the rule is > the > > Trickle timer defined in [RFC6206] which is applied on DIO > messages > > [RFC6550]. However, any such algorithm of limiting the broadcast > > > > nit(?): "One of the algorithms that fulfills this requirement"? > > > > > will update accordingly. > > > > MSF RECOMMENDS the use of 3 slotframes. MSF schedules autonomous > > cells at Slotframe 1 (Section 3) and 6P negotiated cells at > Slotframe > > 2 (Section 5) , while Slotframe 0 is used for the bootstrap > traffic > > as defined in the Minimal 6TiSCH Configuration. It is > RECOMMENDED to > > use the same slotframe length for Slotframe 0, 1 and 2. Thus it > is > > > > Perhaps this is just a question of writing style, but if an > > implementation is free to use an alternative SF or a variant of MSF, > > could we not say that "MSF uses 3 slotframts", "MSF uses the same > > slotframe length for", etc.? > > > > > updated to "3 slotframes are used in MSF. " , "The same slotframe > length > > for Slotframe 0, 1 and 2 is RECOMMENDED". > > > > Section 3 > > > > Is there any risk of unwanted correlation between slot and channel > > offsets when using the same hash function and input for both > > calculations? > > > > hash function. Other optional parameters defined in SAX > determine > > the performance of SAX hash function. Those parameters could be > > broadcasted in EB frame or pre-configured. For interoperability > > purposes, an example how the hash function is implemented is > detailed > > in Appendix B. > > > > Given the lack of usable reference for [SAX-DASFAA], I assume that > the > > content in Appendix B is going to be used as a specification, not > just > > an example. > > > > > the new reference for SAX is updated in the new revision. > > > > * The AutoRxCell MUST always remain scheduled after > synchronized. > > > > nit: s/synchronized/synchronization/ > > > > AutoRxCell. In case of conflicting with a negotiated cell, > > autonomous cells take precedence over negotiated cell, which is > > stated in [IEEE802154]. However, when the Slotframe 0, 1 and 2 > use > > the same length value, it is possible for negotiated cell to > avoid > > the collision with AutoRxCell. > > > > Presumably this factors in to the recommendation to have the three > > listed slotframes use the same length, but mentioning it explicitly > > (whether here or where the recommendation is made) might be nice. > > > > > it is mentioned before as: The same slotframe length for Slotframe > 0, 1 > > and 2 is RECOMMENDED. > > I agree that it is mentioned before. My point is that we have the > recommendation to use the same slotframe length (Section 2) in a different > place from discussion about why having the same slotframe length is > beneficial (here), so the reader has to remember and make the connection. > If we mention both the recommendation and the reason for the recommendation > in the same place, the reader has to do less work. > *RESPONSE:* Agreed. Will add following sentence in the text. However, when the Slotframe 0, 1 and 2 use the same length value, it is possible for negotiated cell to avoid the collision with AutoRxCell. *Hence, the same slotframe length for Slotframe 0, 1 and 2 is RECOMMENDED.* > > > Section 4 > > > > network. Alternative behaviors may involved, for example, when > > alternative security solution is used for the network. Section > 4.1 > > > > nit: singular/plural mismatch "behaviors"/"solution is used" > > > > > will be fixed in next revision. > > > > Section 4.1 > > > > A node implementing MSF SHOULD implement the Minimal Security > > Framework for 6TiSCH [I-D.ietf-6tisch-minimal-security]. As a > > > > Didn't this get renamed to CoJP? > > > > > Thanks for pointing it out! Will update in next revision. > > > > Section 4.2 > > > > I a little bit wonder if there is a better description than > "available > > frequencies" but don't have one to offer. > > > > > The frequency to be selected is randomly picked. There is no one > that is > > preferred comparing to others. > > I was not sure if this was "available" in the sense of "my hardware radio > has a list of frequencies that it can tune to", "the channels that my > network cycles amongst", or " the channels not already scheduled at this > time". > *RESPONSE: * The second is what the sentence tries to convey. Does the following sentence is clear for you then? *When switched on, the pledge randomly chooses a frequency from the channels that the network cycles amongst, and starts listening for EBs on that frequency.* > > Section 4.3 > > > > While the exact behavior is implementation-specific, it is > > RECOMMENDED that after having received the first EB, a node keeps > > listen for at most MAX_EB_DELAY seconds until it has received EBs > > from NUM_NEIGHBOURS_TO_WAIT distinct neighbors, which is defined > in > > [RFC8180]. > > > > nit(?): this phrasing implies that only NUM_NEIGHBOURS_TO_WAIT is > > defined in RFC 8180, but MAX_EB_DELAY is also defined there. > > > > > The "which" here indicates the whole behavior. > > > It will be rephrased as "This behavior is defined in [RFC8180]". > > > > not-nit: this phrasing is ambiguous as to whether one of > MAX_EB_DELAY > > and NUM_NEIGHBOURS_TO_WAIT is sufficient to move to the next step or > > whether both are required. > > > > > The two are actually explaining two situations: > > > 1 .keep listening, when EBs from NUM_NEIGHBOURS_TO_WAIT are > received, it > > stops listening and synchronize to one of the neighbors . > > > 2. if after MAX_EB_DELAY timeout, EBs are received from number of > > neighbors < NUM_NEIGHBOURS_TO_WAIT, it stops listening as well and > > synchronize to the neighbor or one of neighbors. > > Okay. I would suggest to s/at most MAX_EB_DELAY seconds until it has > received/at most MAX_EB_DELAY seconds or until it has received/, then. > *RESPONSE: * I agree to use "or" here. This sentence is the original sentence from RFC8180. Can I update the sentence by using "or" in this draft? > > Also, I se that the -14 has changed this from RECOMMENDED to MAY; my naive > expectation would be that it is still RECOMMENDED, but I don't remember if > another reviewer's comment prompted this change. > *RESPONSE:* it is mentioned by one of the reviewers saying it's not consistent with RFC8180. This behavior comes from RFC8180, which uses MAY here. > > > Section 4.4 > > > > After selected a JP, a node generates a Join Request and > installs an > > AutoTxCell to the JP. The Join Request is then sent by the > pledge to > > its JP over the AutoTxCell. The AutoTxCell is removed by the > pledge > > > > editorial: I'd suggest s/its JP/its selected JP/ > > > > > Will be updated in next revision. > > > > Response is sent out. The pledge receives the Join Response > from its > > AutoRxCell, thereby learns the keying material used in the > network, > > as well as other configurations, and becomes a "joined node". > > > > nit: maybe "other configuration values" or "other configuration > > settings"? > > > > > Will be updated in next revision. > > > > Section 4.6 > > > > Once it has selected a routing parent, the joined node MUST > generate > > a 6P ADD Request and install an AutoTxCell to that parent. The > 6P > > ADD Request is sent out through the AutoTxCell with the following > > fields: > > > > * CellOptions: set to TX=1,RX=0,SHARED=0 > > * NumCells: set to 1 > > * CellList: at least 5 cells, chosen according to Section 8 > > > > Is this listing describing the contents of the ADD request or the > > AuthTxCell used to send it? (I presume the former, in which case I > > suggest to use "containing" or similar in preference to "with".) > > > > > yes, it is the former. Will update in the next revision. > > > > Section 5.1 > > > > The goal of MSF is to manage the communication schedule in the > 6TiSCH > > schedule in a distributed manner. For a node, this translates > into > > monitoring the current usage of the cells it has to the selected > > parent: > > > > Is this goal strictly limited to traffic "to the selected parent" > vs. > > all traffic? > > > > > Theoretically MSF does not limit to traffic to the selected parent > but > > any neighbors. > > > However, all the experiment result with MSF we have made to verify > it is > > to the selected parent only. > > > Hence, We state here "the selected parent" only. > > I think the stated scope of applicability of the specification is not > limited to just the experiments that have been performed so far, so there > does not seem much justification for saying that "this translates into > monitoring [...] to the selected parent". > *RESPONSE: *will update the text as following. For a node, this translates into monitoring the current usage of the cells it has to *one of its neighbors, most cases to the selected parent. * > > > * If the node determines that the number of link-layer frames > it is > > attempting to exchange with the selected parent per unit of > time > > is larger than the capacity offered by the TSCH negotiated > cells > > it has scheduled with it, the node issues a 6P ADD command to > that > > parent to add cells to the TSCH schedule. > > * If the traffic is lower than the capacity, the node issues a > 6P > > DELETE command to that parent to delete cells from the TSCH > > schedule. > > > > As written, this would potentially lead to oscillation when demand > is > > basically at capacity, due to the quantization of capacity. Perhaps > > some provisioning for hysteresis is appropriate? > > > > > Yes, if referring to the MSF cell usage algorithm in the following, > more > > cell are scheduled than what needed. > > > Here is to explain the basic concept of this scheduling function. > > > > The cell option of cells listed in CellList in 6P Request frame > > SHOULD be either Tx=1 only or Rx=1 only. Both NumCellsElapsed > and > > NumCellsUsed counters can be used to both type of negotiated > cells. > > > > Would this be more clear as "(Tx=1,Rx=0) or (Tx=0,Rx=1)"? > > > > > Yes it's more clear. Will update in next revision > > > > * NumCellsElapsed is incremented by exactly 1 when the current > cell > > is AutoRxCell. > > > > This holds for all peers/parents we're keeping counters for, so the > > AutoRxCell can get "double counted"? > > > > > one pair of counters is associated to one neighbor. > > > If there is multiple parents, then there are two NumCellsElapsed > > counters, one for each of the parents. > > I agree. It seems that when an AutoRxCell occurs, the NumCellsElapsed > counter will increment in all of the counters (i.e., for each parent). > This is in some sense "double counting" that cell. I'm not sure whether > this has a negative effect on the usefulness of the statistics, especially > in the (unlikely) case when there are a large number of parents. > *RESPONSE:* probably just more memory occupation? Don't know either on the negative effect :-) > > > In case that a node booted or disappeared from the network, the > cell > > reserved at the selected parent may be kept in the schedule > forever. > > A clean-up mechanism MUST be provided to resolve this issue. The > > clean-up mechanism is implementation-specific. It could either > be a > > periodic polling to the neighbors the nodes have negotiated cells > > with, or monitoring the activities on those cells. The goal is > to > > confirm those negotiated cells are not used anymore by the > associated > > neighbors and remove them from the schedule. > > > > I'm not sure that "monitoring the activities on those cells" is safe > > with the current level of specification; if a node negotiates a 6P > > transmit cell to a parent and uses it only sparingly, with the > parent > > eventually reclaiming it due to inactivity, I don't see a mechanism > by > > which the node will reliably discover the negotiated cell to be > > nonfunctional and fall back to (e.g.) the corresponding > AutoTxCell. It > > may be most prudent to just not mention that as an example (a > "periodic > > polling" procedure does not seem to have the same potential for > > information skew) > > > > > Thanks for the comment! I will just remove that sentence from this > > paragraph. > > > > Section 5.3 > > > > schedule is executed and the node sends frames to that parent. > When > > NumTx reaches MAX_NUMTX, both NumTx and NumTxAck MUST be divided > by > > 2. For example, when MAX_NUMTX is set to 256, from NumTx=255 and > > NumTxAck=127, the counters become NumTx=128 and NumTxAck=64 if > one > > frame is sent to the parent with an Acknowledgment received. > This > > operation does not change the value of the PDR, but allows the > > counters to keep incrementing. The value of MAX_NUMTX is > > implementation-specific. > > > > Does MAX_NUMTX need to be a power of two (to avoid errors when the > > division occurs)? > > > > > Agree, it's better to be a power of two. Will state in the text. > > > > 4. For any other cell, it compares its PDR against that of the > cell > > with the highest PDR. If the difference is larger than > > RELOCATE_PDRTHRES, it triggers the relocation of that cell > using > > a 6P RELOCATE command. > > > > The recommended RELOCATE_PDRTHRES is given as "50 %". Is this > > "difference" performed as a subtraction (so that if the highest PDR > is > > less than 50%, no cells can ever be relocated) or a ratio (a PDR > that's > > half than the maximum PDR or smaller will trigger relocation)? > > > > > This is "difference" performed as a subtraction. > > > Yes it's sure if highest PDR is less than 50%, no cell can be > > relocated. > > > But it can't tell those cells are link quality bad or because of > > collision. > > > If all cell PDR is so low, highly chance the routing will be > affected > > and switch to another neighbor. > > > In experiments, we never encounter highest PDR less 50% all time. > > I strongly suggest changing the wording to be clear that it is the > "subtraction" interpretation that's desired. Perhaps "If the difference > (PDR_highest - PDR_thiscell) is larger than RELOCATE_PDRTHRES"? > RESPONSE: it will be rephrased as following: If *the subtraction difference between the PDR of the cell and the highest PDR* is larger than RELOCATE_PDRTHRES, it triggers the relocation of that cell using a 6P RELOCATE command. > > > Section 7 > > > > Maybe reference Section 17.1 where the allocation will occur? > > > > > Will add this in next revision. > > > > Section 8 > > > > * The slotOffset of a cell in the CellList SHOULD be randomly > and > > uniformly chosen among all the slotOffset values that satisfy > the > > restrictions above. > > * The channelOffset of a cell in the CellList SHOULD be > randomly and > > uniformly chosen in [0..numFrequencies], where numFrequencies > > represents the number of frequencies a node can communicate > on. > > > > Do these random selections need to be independent from each other? > (I > > note that the selection for the autonomous cells are not.) > > > > > For channelOffset, they are independently random selected. > > > For slotOffset, since once a slotOffset is picked, the next time to > > select slotOffset, that one can't be selected. > > > This is indicated in the text already as "chosen among all the > > slotOffset values that satisfy the > > restrictions above" > > I was trying to get at a different point, I think: is there expected to be > correlation between the actual slotOffset and channelOffset values for a > given cell, as opposed to having them be completely independent selections? > In the case of the autonomous cells, since we use the same hash function > and input to the hash function for selecting both values, there is a > correlation between the two values. Such a correlation might in theory > result in occasional problematic scenarios that are very problematic, > whereas if the channel and slot offsets are chosen independently, such > "very problematic" scenarios are expected to be much less common (based on > the obvious/naive mathematical model). > *RESPONSE:* I agree there is potential correlation between the slotoffset and channel offset as using the same hashing function. However, the (slotoffset, channeloffset) is general considered as one item, called a cell. As long as there is no correlation between cells, there should be no problems. > > > > > Section 9 > > > > Is there a reference for these three parameters (MAXBE, MAXRETRIES, > > SLOTFRAME_LENGTH)? SLOTFRAME_LENGTH seems new in this document and > is > > listed in the table in Section 14, but the other two are not listed > > there. > > > > > The MAXBE, MAXRETRIES are defined in IEEE802.15.4 standard. > > > Their values various on different network systems, according to the > size > > and density. > > > Hence we didn't give a recommended value in this draft. > > Ah, I see now. It might be helpful to note somewhere that MAXBE and > MAXRETRIES are defined by 802.15.4, though I expect most readers of this > document to already be at least somewhat familiar with 802.15.4. > *RESPONSE: *will be mentioned in the draft. > > > Section 14 > > > > Why is MAX_NUMTX not listed in the table? > > Should MAX_NUMTX be listed in the table? > *RESPONSE: *it's listed in version 14. > > > Can we really give a recommended NUM_CH_OFFSET value, since this is > in > > effect dependent on the number of channels available? > > > > > We give a recommended value as this is a parameter used in the SAX > > hashing algorithm. > > > This doesn't provide implementer to use other values. > > > > KA_PERIOD is defined but not used elsewhere in the document. > > > > > This is a legacy of MSF draft, which we forgot to remove. Will > update in > > next revision > > > > What are the considerations in using a power of 10 vs. a power of 2 > as > > MAX_NUM_CELLS? > > > > > We pick power of 10 simply because it's easy for reader to > understand. > > Nothing specific. > > > There is no restriction to use power of 2, such as 128. > > > > Section 16 > > > > MSF defines a series of "rules" for the node to follow. It > triggers > > several actions, that are carried out by the protocols defined > in the > > following specifications: the Minimal IPv6 over the TSCH Mode of > IEEE > > 802.15.4e (6TiSCH) Configuration [RFC8180], the 6TiSCH Operation > > > > I'd suggest a brief note that the security considerations of those > > protocols continue to apply (even though it ought to be obvious); > > reading them could help a reader understand the behavior of this > > document as well. > > > > Sublayer Protocol (6P) [RFC8480], and the Minimal Security > Framework > > for 6TiSCH [I-D.ietf-6tisch-minimal-security]. In particular, > MSF > > > > [CoJP again] > > > > prevent it from receiving the join response. This situation > should > > be detected through the absence of a particular node from the > network > > and handled by the network administrator through out-of-band > means, > > e.g. by moving the node outside the radio range of the attacker.. > > > > "the radio range of the attacker" is not exactly a fixed constant > ... > > attackers are not in general bound by legal limits and can increase > Tx > > power subject only to their equipment and budget. > > > > > Yes, I agree. For action, I will simply remove the example. > > > > MSF adapts to traffics containing packets from IP layer. It is > > possible that the IP packet has a non-zero DSCP (Diffserv Code > Point > > [RFC2597]) value in its IPv6 header. The decision whether to > hand > > > > RFC 2597 is talking more about specifically assured forwarding PHB > > groups > > than "DSCP codepoint"s per se. > > > > > Yes, RFC2472 is the one defined the DSCP codepoint. Will update the > > reference. > > This text was also changed to fix a pluralization nit, but over-corrected.. > Please s/containing packet/containing packets/. > *RESPONSE*: Will be updated in next revision. > > > Section 18.1 > > > > RFC 6206 seems to only be used as an example (Trickle), and could > > probably be informative. > > > > RFC 8505 might also not need to be normative. > > > > > They will be moved to informative reference section > > > > Appendix B > > > > In MSF, the T is replaced by the length slotframe 1. String s is > > > > nit: "length of" > > > > 2. sum the value of L_shift(h,l_bit), R_shift(h,r_bit) and ci > > > > Is this addition performed in "infinite precision" integer > arithmetic or > > limited to the output width of h, e.g., by modular division? (It's > not > > clear to me whether this is the role T plays or not.) > > > > > What I know here the sum is used by most of the classic string > hashing > > functions. > > > The deep reason why using sum here is more mathematics question, > which I > > am not an expertise on it:-( > > > The T here used for modular is to make sure the result fall into the > > range of slotframe ( to pick slotOffset), or available frequencies ( > to > > pick channelOffset). > > It sounds like this sum is performed modulo T as well? (I am genuinely not > sure.) I'm also not sure whether it's worth mentioning that fact; perhaps > just leaving the text as-is is best. > > 8. assign the result of Step 5 to h > > > > The value from step 5 *is* h, so taken literally this says "assign > h to > > h" and is not needed. > > > > > Yes, this step is removed in next revision. > > Thanks so much for your comments. Will prepare revision 13 to resolve > > them! > > Thank you for the updates! > > I will await further clarification about whether changes to > draft-ietf-6tisch-minimal-security are required in order for this document > to realistically be able to meet the requirements from that document. > > -Ben > *RESPONSE*: thanks again for your feedback on the draft! -- —————————————————————————————————————— Stay healthy, stay optimistic! Dr. Tengfei, Chang Postdoctoral Research Engineer, Inria www.tchang.org/ ——————————————————————————————————————
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