Re: [dhcwg] Comments on 22 rev of the draft
Vijay Bhaskar A K <vijayak@india.hp.com> Fri, 18 January 2002 17:45 UTC
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From: Vijay Bhaskar A K <vijayak@india.hp.com>
Message-Id: <200201181738.XAA16245@dce.india.hp.com>
Subject: Re: [dhcwg] Comments on 22 rev of the draft
To: Bernie.Volz@am1.ericsson.se
Date: Fri, 18 Jan 2002 23:08:15 +0530
Cc: vijayak@india.hp.com, Bernie.Volz@am1.ericsson.se, dhcwg@ietf.org
In-Reply-To: <66F66129A77AD411B76200508B65AC69B4CDB4@EAMBUNT705> from Bernie Volz at Jan "17, " 2002 "12:10:39" pm
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Bernie, See my comments prefixed by VB2> ~ Vijay > Vijay, see BV2> comments. > > - Bernie > > -----Original Message----- > From: Vijay Bhaskar A K [mailto:vijayak@india.hp.com] > Sent: Thursday, January 17, 2002 4:35 AM > To: Bernie.Volz@am1.ericsson.se > Cc: vijayak@india.hp.com; dhcwg@ietf.org > Subject: Re: [dhcwg] Comments on 22 rev of the draft > > > See my comments inline prefixed by VB> > > ~Vijay > > > Let me try to answer these based on my understanding/view of -22. > > > > See below. > > > > - Bernie > > > > -----Original Message----- > > From: Vijay Bhaskar A K [mailto:vijayak@india.hp.com] > > Sent: Wednesday, January 16, 2002 1:05 PM > > To: dhcwg@ietf.org > > Cc: vijayak@dce.india.hp.com > > Subject: [dhcwg] Comments on 22 rev of the draft > > > > > > I had gone through the latest rev of DHCPv6 draft. Sorry for the delay > > in telling the comments. > > > > - I think we need to fix the order of occurence some options that can > > appear in the dhcp messages. I think, the DUID option should occur > > before the IA option. This makes the processing simpler. > > > > BV> I think this would be good to say that a client MUST place the DUID option in a mesage before any IA options. > > > > - I didn't get, why the authentication option should be the last one. I > > feel like it should be the first one. If the server/client is not able > > to validate the authentication, it can straight away discard the packet > > without further processing. > > > > BV> I too wouldn't mind having this earlier. It makes it easier to validate messages since one doesn't have to process all of the options (or at least parse to some extent all of the options) before one can authenticate the message. But, I would call this a SHOULD not a MUST. > > VB> I would like to call this MUST rather than SHOULD, because, this > authentication model of DHCP came only for avoiding DoS attacks. The > server should not waste its time in processing these spurious packets. > > > > > - Section 13 says the ways for selecting addresses for assignment in > > IAs. Assume, the server has got a direct message from the client. The > > IP datagram source address is a site-local one. The message is received > > on the server's interface, which is configured with a global address. > > According to the draft, the server should assume that the client is on > > the link identified by the sitelocal address in datagram. Now, the > > problem arises, if the server is not configured for allocating > > site-local address for the link. Now, can the server assume, since the > > client has sent the direct message, it is on the same link as the server > > and assign it an address of global scope, with the same prefix of its > > received interface. I think, i have already raised the similar kind of > > problem previously, the answer i had got was to select address of global > > scope. Then, the server should not select the link based on the source > > address. This is an implementation problem we faced. FYI, HP has > > officially released DHCPv6. This implementation is based on 16th and > > some portion of 18th version of the draft. This software is freely > > available at http://software.hp.com/ You can download it and tell me > > your comments. > > > > BV> Section 13 tells how to determine the *LINK* the client is on. Once > > that has been done, you assign addresses based on the prefixes that the > > server has configured for that *LINK*. If the source address for the > > DHCP message was a link local, the server knows that it can't have come > > from anywhere but that link (since link-local are only valid locally). > > But this only determines the LINK for the client; not the addresses. > > VB> Assume the scenario where the server and client are in same link. > The configuration of server's interface and client interface is as > follows. > > server lan0 - fe80::260:b0ff:fec1:bb6b (A link local address) > server lan0:1 - 3ffe::12 (A global address) > client lan0 - fe80::210:83ff:fe18:886f (A link local address) > client lan0:1 - fec0::1234:27 (A site local address) > > server lan0 and client's lan0 are in same link. Now the client decides > to get an IP address from dhcp server. So, it puts the site local > address (lan0:1 addr) in the IP datagram src address field and sends the > SOLICIT message. Assume, the server is configured to allocate only > global address of prefix 3ffe::/64 for that link. But, according to the > draft, it finds out that the message comes from fec0::1234:27/64 > network, finds out it is not supposed to serve that network and hence it > does not send advertise. What i feel is, since the allocation for > normal addresses are dictated by server's policy, let the server dictate > completely. let it not to give any preference to client's wish. In the > above situation, if the server is not noticing the src address in IP > datagram of the client, it can find out that the client is on the same > link as the server, since it is a direct message. Thus, it can allocate > allocate address of prefix 3ffe::/64. Since the SOLICIT message is sent > to All DHCP Agents Address, if the server receives the client message > directly, then, the client is in the same link. Thus, the decision of > the link based on the IP datagram src address of the client is not at > all necessary. > > BV2> Again, all the server does is use the address to determine the LINK. > So, the server needs to know about the site local prefix being active on > the link but that's all. If the server fails to find the prefix for the > address, it can either drop the request or it could simply assume it must > have come from the LINKs associated with the interface the packet was > received on. So, it is happy. > > Note that the client really should be using the link local address UNLESS > it is unicasting to a server (in which case it must use an address of > sufficient scope valid for the server to send replies). The All DHCP > Agents address is link scoped, so the source address only needs to be > linked scoped as well. > > So, I don't see any issues here. Or am I failing to understand your concern? VB2> What i mean is, for finding the link, server should not trust client. It knows the link where it is received. Based on its own address in the link, it should allocate address to the client. The client may not be knowing where it is. Sometimes, what it has may be wrong. So, the src address in IP datagram may show wrong information. VB2> Assume, a client is moving from the 3ffe::/64 network to 5ffe::/64 network. As per the draft, it will the confirm message. 16.2.2 says that, the server will just compare the binding info it's having with the one in confirm message. I think the server MUST check the prefix also. It must check whether the addresses in the IA are having the same prefixes of the link in which the client is connected to. I think, no where in the draft, the draft is not dealing with the prefix comparison of the link and IA addresses. So, in this case, the server sends a positive reply. The client wont get it, because, it does have a valid address to receive it. VB2> After some time, if it requires another address, it will send a new request with the src address with 3ffe::/64 prefix and hence the server allocates the address with 3ffe::/64 prefix for the 5ffe::/64 network. I think the neat and clean way of client asking for the addresses in a particular prefix, is sending through an option, similar to subnet selection option (RFC 3011). I can include the text for this option. This is one of the option, i have forgetten to tell in the previous mail. > > > > > - Using DUID, how the address selection is done? > > > > BV> I don't understand what you are asking here. > > > > - The draft says that, when the client needs an additional temporary > > address, it can include OPTION_RTA encapsulated in OPTION_IA and get the > > additional one. This means, in the same IA, any number of addresses can > > be can be added and deleted. Will it hold for normal addresses also? I > > mean, for additional normal addresses, whether the client has to use > > already existing IA to get additional address (or) will it use a fresh > > IA? I remember that, the answer i got for this question 3-4 months back > > was that the client will use fresh IA, because, adding address to the > > same IA will lead complexity. Just in curiosity, i am asking, why this > > complexity was introduced for temporary addresses? Why can't the client > > can ask additional temporary addresses in a fresh IA? > > > > BV> We do NOT want IA explosion. Ideally, a client should be able to use > > the same IA forever under "normal" cases. A IA can have one or many > > addresses, addresses will come and go. Server policy dictates the non- > > temporary addresses assigned to a client. Client policy dictates the > > temporary address needs - hence the client must have a way to say > > "give me more". For example, if a client is running two applications that > > each want unique temporary addresses, it has to request those from the > > server. Later, when a third application starts, the client will need > > another address. > > > > - Can temporary addresses and normal addresses can co-exist in same IA? > > If yes, then, for renewal, does the client send normal addresses alone > > in IA to the server? since, the renewal of temporary addresses is > > meaningless. > > > > BV> YES the can both be in the SAME IA. That is the intention. > > > > - I thought for decreasing the load of server, unlike DHCPv4, in DHCPv6, > > the dns updates was moved to client. But, the draft says that, for > > temporary addresses, the server has to update the DNS. Why this feature > > was included in server, instead of client? > > > > BV> What we say in section 14 is: > > > > The server MAY update the DNS for a temporary address as described in > > section 4 of RFC3041, and MUST NOT update the DNS in any other way > > for a temporary address. > > > > BV> This all depends how DDNS is handled with DHCPv6 and who is doing the > > updates. We just wanted to be clear that if the server was doing DDNS > > updates for the client, is must adhere to the requirements of RFC 3041 > > in doing them!! > > > > - Why only temporary has to be updated in DNS? why not normal > > addresses? > > > > BV> See answer to previous question. DDNS updates are still TBD. Likely > > the DHCPv4 FQDN option will be used (changing the A processing to reflect > > AAAA processing and using the DUID for the client identification). > > > > - I think for updation, we need to define, hostname/FQDN option for > > this. > > > > BV> Yes, we will need this. > > > > - How can the client specify the number of address it wants? Will it > > send IA optio with 'n' number empty of IA_ADDR option? Instead of that, > > can we define another option OPT_RA similar to OPT_RTA, that can be > > encapsulated in OPT_IA? > > > > BV> The client can't specify how many non-temporary addresses it wants. > > This is controlled by the server. The client *CAN* use multiple IAs and > > if the server policy allows, that can easily be used to give the clients > > LOTS of addresses (one set per IA). > > > > - Section 17.1.2 says that the client collects Advertise messages until > > SOL_TIMEOUT has elapsed. Then, RT will be recalculated. Now, does the > > client needs to retransmit the SOLICIT message? If it is so, then, the > > same server will reply multiple times. But the retransmission algorithm > > in Section 15 says that, it should retransmit the packet. > > > > BV> The client waits SOL_TIMEOUT but it does not retransmit the Solicit > > if it has received at least one Advertise. Retransmit Solicit only if no > > Advertise messages are received. > > VB> The Algorithm in section 15 says that, it should retransmit at the > expiration on RT. The variation for SOLICIT on this algorithm in > 17.1.2, does not say anything about this. So, it is better to add the > statement you have stated above, in the draft also for better clarity. > Otherwise, it is misleading. > > BV2> I will review the text again to see if this was not clear. > > > > > - In section 17.1.2, we need to add a sentence, "When the RT reached > > MRT, if the one or more valid advertise message is obtained, the client > > should stop sending Advertise message and proceed further with collected > > Advertise message". Otherwise, since MRC and MRD are 0, this process > > will go infinetly according to algorithm specified in Section 15. This > > is also an implementation problem we faced. > > > > BV> Haven't studied this issue. > > > > - In some place, the server should fill "server-address" with one of its > > address based on the link in which the packet is received. In another > > place, it is said that the server-address field can be filled with the > > address configured by the administrator. What is the standard procedure > > to be followed? > > > > BV> We probably should clean up the text to be consistent. I think the > > answer is use configured address if so configured for that LINK, otherwise > > use one of the LINK interface addresses. > > > > - In Advertise, should the server assign all the addresses asked by the > > client? (or) only few of them? > > > > BV> It depends on the server's policies. > > > > - Till what time, these OFFERED addresses are preserved for those > > clients to assign? > > > > BV> My opinion is that the ADVERTISED addresses are just a possible set of > > addresses the client will get and may not be the exact addresses. The client > > must wait until the Reply to the Request before it knows which addresses it > > got and before it does Duplicate Address Detection. The ADVERTISE should > > include all of the parameters the client is likely to receive in the Reply, > > but they are just possible values and not the actual values. > > VB> What i am asking is, in V4, there is a concept called OFFERED > addresses, which will be reserved to a client. The server reserves that > addresses for the some predefined time. At the expiration of the time, > if the client has not sent the request, it will be allocated to some > other clients. I think, if we follow the same policy, it will be > better. Assume, a client sends a SOLICIT and the server replies with > ADVERTISE with some addresses. Before the client sending the Request, > if some other client requests for the addresses, with the current > mechanism, the server will assign the addresses to new client. It may > lead to server to send AddrUnavail to the first client, if the server > has only limited number of addresses. It will lead to unnecessary > packet transactions. > > BV2> I don't agree. It is much better if the server can just send something > out and not have to do anything to remember it. With IPv6, what's the likelyhood > that an address won't be available - we have 2^64 addresses on each prefix! > > BV2> What I view the ADVERTISE message to be is for the server to say I am > willing to give you this stuff [assuming it is avaiable] but that I haven't > given you the EXACT stuff you will get (since that happens in the Reply to > the Request). > > BV2> BUT please note that this really is up to each SERVER to do what it > wants. A SERVER can chose to ADVERTISE real stuff and "reserve" it for some > period of time (and that is a SERVER implementation issue). In my server, > I might chose that time to be 0 seconds. In your server, you can set it to > 1 hour. The client can't do anything with ADVERTISEd information other than > make a decision based on which ADVERTISE it wants to accept (assuming it gets > multiple). In any case, the information from the Reply is what it must install. > So, this is purely a server implementation issue. VB2> Yes. I agree that this is purely an implementation issue. > > > > > - If the server has fewer addresses than the client has asked, will the > > server assign fewer addresses or send AddrUnavail? > > > > BV> I would only return AddrUnavail if NO addresses are available. If you > > can assign some, give the client those. It can make a decisions as to > > whether it wants to accept them or not. > > VB> agreed. > > > > > - The draft says that the renew message can be used for checking up the > > validity of the other configuration parameters. For checking the > > validity of them, will the client send the option codes in ORO option > > (or) send the parameters in their respective options? > > > > BV> The Renew message does not need to include those options (including > > them in an ORO is probably a good idea so the server knows you want them). > > It is really the Reply that matters and the server will Reply with the > > current settings. The client can then apply those values. The server will > > (I suspect) not really check them - it just Replies with the current > > values. > > VB> Sending the ORO option is best idea. I think we need to add the > mechanism of renewal of other parameters (sending ORO option) in the > draft. > > BV2> Yeah, but that is already clear. See 22.6 (ORO option) text. And also > Appendix B VB2> Agreed > > few addresses be relased from an IA? (partial release) > > > > BV> Individual addresses can be released or declined. The client MUST > > include the addresses to decline/release. The server ignores any addresses > > that the client doesn't "own". > > > > - Assuming the client is sending multiple IAs for renewing, the server > > finds that one particular IA is not found in the client bindings, will > > it renews the remaining IAs? (or) will it send NoBinding error? > > > > BV> It can send a NoBinding status for that IA. (And renew the others.) > > > > - What will the client do, for the multiple IAs sent for renew, only one > > IA is missing in the reply? > > > > BV> No sure what you asking? Is this a follow up to the previous question? > > If the IA returns with a NoBinding status, the client may either continue > > to use those addresses (since it must have gotten them from someone in the > > past) or drop them (and the IA). > > > > - Can you explain the differnce between, "configuration information are > > not valid" and "configuration information does not match". In the first > > case, for Confirm message ConfNoMatch is sent and for the next one, it > > is sending SUCCESS. The draft says that for ConfNoMatch, the client > > should send renew message. If the configuration parameters are not > > matching, then what is the use of sending renew message? > > > > BV> Have to look into this one more. > > > > - For the cases like, "conf parameters are not valid", "conf parameters > > does not match" and "prefix does not match", what will the server do, > > for the release message? What will the server do? if (i) all, (ii) only > > few addresses are invalid. Will the server release the address which > > are valid? > > > > BV> Have to look into this one more. > > > > - Section 21.6.5.5 says that, if the client is not able to validate the > > authentication for the REPLY message, then it should start with the > > SOLICIT. I feel that this is inefficient, instead, it can try the next > > available server which has sent the advertise message. > > > > BV> Have to look into this one more. > > > > - In the previous versions, we have Retransmission Parameter option. > > Why it was removed? > > > > BV> There are significant security / DOS issues with allowing the server > > to set parameters. Also, there are issues as when these parameters are to > > be used (vs the defaults). If a client moves to a completely different > > DHCP domain, the parameters may not be valid and how does it know that? > > VB> Agreed > > > > > - Some useful options were defined in DHCPv6 extension draft. When will > > those options be included in this draft? > > > > BV> Suggest the ones you want to have included! Provide the text (if it > > needs to be revised). That's what Ralph (as editor) has requested in the > > past. > > VB> I think, there are some basic configuration parameters for the host > to work comfortably. We can add options for getting those configuration > parameters. The options are, > > NIS, NIS+, NTP server addresses, SLP DA addresses and its scope list. > NIS and NIS+ client domain name, Time Zone. > hostname,FQDN,static route option. > > If you are agreeing in adding these options to base spec,i can provide > the text. > > BV2> Supply proposed text (similar to the existing Options sections). If you don't > supply it, the options won't be in the base spec. If you do, it will just depend on > what the WG thinks of them. I don't really see any significant reason not to include > the ones you propose. I think the major issue is to have a clear reason for the option > and to assure it is well define/specified. One tactic that has been used is to wait > to define the options until a clear need is found (since then a clearer specification of > the option can be written!). VB2> I am sending it in a seperate mail. -- ____Vijay_Bhaskar_A_K____ ______Inet_Services______ ________HP_ISO___________ ______Ph:_2051424________ ____Telnet:_847_1424_____ ___Pager:_9624_371137____ _______________________________________________ dhcwg mailing list dhcwg@ietf.org https://www1.ietf.org/mailman/listinfo/dhcwg
- [dhcwg] Comments on 22 rev of the draft Vijay Bhaskar A K
- RE: [dhcwg] Comments on 22 rev of the draft Bernie Volz (EUD)
- RE: [dhcwg] Comments on 22 rev of the draft Ralph Droms
- Re: [dhcwg] Comments on 22 rev of the draft Vijay Bhaskar A K
- Re: [dhcwg] Comments on 22 rev of the draft Vijay Bhaskar A K
- RE: [dhcwg] Comments on 22 rev of the draft Bernie Volz (EUD)
- RE: [dhcwg] Comments on 22 rev of the draft Bernie Volz (EUD)
- Re: [dhcwg] Comments on 22 rev of the draft Vijay Bhaskar A K
- Re: [dhcwg] Comments on 22 rev of the draft Vijay Bhaskar A K
- RE: [dhcwg] Comments on 22 rev of the draft Bernie Volz (EUD)
- RE: [dhcwg] Comments on 22 rev of the draft Vijayabhaskar A K
- RE: [dhcwg] Comments on 22 rev of the draft Bernie Volz (EUD)
- Re: [dhcwg] Comments on 22 rev of the draft Ralph Droms
- Re: [dhcwg] Comments on 22 rev of the draft Vijay Bhaskar A K
- Re: [dhcwg] Comments on 22 rev of the draft Vijay Bhaskar A K
- Re: [dhcwg] Comments on 22 rev of the draft Ted Lemon
- Re: [dhcwg] Comments on 22 rev of the draft Vijay Bhaskar A K
- Re: [dhcwg] Comments on 22 rev of the draft Ted Lemon
- Re: [dhcwg] Comments on 22 rev of the draft Ted Lemon
- Re: [dhcwg] Comments on 22 rev of the draft Martin Stiemerling
- Re: [dhcwg] Comments on 22 rev of the draft Jim Bound
- Re: [dhcwg] Comments on 22 rev of the draft Martin Stiemerling
- [dhcwg] Question on DHCPv6 Draft 23. Paul Tan