Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configuration-02.txt
<ian.farrer@telekom.de> Tue, 29 October 2013 13:44 UTC
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From: ian.farrer@telekom.de
To: otroan@employees.org
Date: Tue, 29 Oct 2013 14:43:53 +0100
Thread-Topic: [dhcwg] I-D Action: draft-ietf-dhc-v4configuration-02.txt
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Subject: Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configuration-02.txt
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Hi Ole, Thanks for the review. I¹ve updated the draft based on your comments. And some more answers in line. Cheers, Ian > >yes, I think a clarification in the introduction would help. >stateful DHCPv4 doesn't apply to DS-lite, and it is difficult to see how >it applies to MAP. >which link-layer did you have in mind for this? >is this work meant to also provide stateful DHCPv4 for MAP tunnels? [ian] It¹s not meant to be limited to any particular softwire or other v4 type. If someone was to have a reason for using stateful DHCPv4 for MAP at some point in the future, then this IPv4 configuration > >e.g. a configured RFC2473 tunnel or Public 4over6, could work. > >when it comes to provisioning of a shared IPv4 address, DHCPv4 doesn't >really do that. >I don't see that described in this document? [ian] The draft¹s concerned with how IPv4 configuration is transported, not what the specific v4 configuration is. >I think we need to evaluate if there should be a completely new option >for IPv4 address and port set, or >a the classic IPv4 address option combined with a new port set option. [ian] There¹s a couple of drafts out there that do this at the moment: draft-sun-dhc-port-set-option & draft-farrer-dhc-shared-address-lease. I think that it¹s better to handle the format and other considerations around option formats and shared address leasing separate from the transport question covered in this draft. > >>> Section 2: >>> Drop requirement 6, I can't see how you can evaluate that. >> >> [ian] You can evaluate it on the following basis: If the requirements >>that are described in this document are not your requirements as an >>operator, then you shouldn't be forced to use whatever the conclusion of >>this document is. In practical terms, I see this as 'if MAP DHCP meets >>your requirements, you don't need to bring in DHCPv4 over Foo or >>whatever else'. > >I didn't quite understand the implications of that. [ian] During the discussion in Atlanta that led up to writing this document, an opinion voiced by several operators was: If I can provision everything I need using simple, static DHCPv6 (I.e. Option map), why should I have the additional overhead of a DHCPv4 providing additional DHCPv4 options and dynamic leasing which is unnecessary to me? The requirement is there to evaluate whether a solution allows you to do that. > >>> 8 is empty >>> >> [ian] Will fix. >> >>> I suggest you add a new requirement: >>> x. Fate sharing. The provisioning of IPv4 addressing and other >>>configuration information should be logically tied >>> to the data-link layer that is uses to provide IPv4 connectivity. >> >> [ian] This one's going to be more of a problem, as it pretty much >>directly conflicts with requirement 7, in that the two contradict each >>other. You can only implement data link fate sharing if you've got a hub >>and spoke architecture to locate the hub in (so that if it's not >>available, then IPv4 provisioning also fails) > >which link-layer fails that? >I'm dubious about requirement 7 overall. and e.g. DHCPv4 over DHCPv6 is >restricted to there being a DHCPv6 transport available. [ian] There¹s a slot for this draft in Vancouver. Can we discuss it there as this has a direct effect on the outcome? > >> In the case of a pure mesh network, with no hub and spoke, how could >>you have fate sharing for the data-link layer? The proposed requirement >>pre-supposes a specific underlying architecture. > >is this the equivalent to the dentist's office case? can you give an >example of other data link-layers where IPv4 can be provisioned on a NBMA >link, without a router? [ian] Not familiar with the Dentist office in this particular context. The obvious example would be a single Ethernet segment with a DHCP server attached, but I¹m not sure how that¹s relevant to this discussion. > >> Can we put this one to the workgroup to ask if this should be included >>as a new req, as it' has not been previously discussed? >> >>> >>> Section 3: >>> DHCPv4oDHCPv6 is "no" for requirement 4. and "no" on fate sharing. >> >> [ian] Why is it a 'no' for req 4? Section 8 of the DHCPv4 over DHCPv6 >>draft: >> >> Additionally, the DHCPv6 relay agent MAY allow the configuration of >> dedicated DHCPv4 over DHCPv6 specific destination addresses, >> differing from the addresses of the DHCPv6 only server(s). To >> implement this function, the relay checks the received DHCPv6 message >> type and forwards according to the following logic: >> >> 1. If the message type is BOOTREQUESTV6, then the DHCPv6 request is >> relayed to the configured DHCPv4 aware 4o6 Server's address(es). >> >> 2. For any other DHCPv6 message type, forward according to section >> 20 of [RFC3315]. > >DHCPv4 over DHCPv6 requires support for transporting DHCPv4 messages in >DHCPv6 servers and clients. [ian] Or, you could add a minimal DHCPv6 encapsulation to a DHCPv4 server. >what do you mean by "independent DHCPv4 and DHCPv6 servers" then? [ian] if you wanted to deploy DHCPv6 servers and DHCPv4overDHCPv6 servers as separate instances, you can. Given how complex the DHCPv6 server logic can become, there¹s some good reasons no to overload the DHCPv6 server with DHCPv4 functions as well. >could you clarify the requirements? >now they do read like they have been reverse engineered. [ian] Extended the definition with an explanation. > >> For the fate sharing req, as stated above. >> >>> >>> In the evaluation in section 3.x I suggest dropping the use of >>>"complex" and "simple". >>> That appears very subjective. >>> >> [ian] OK >> >>> 3.4.2 bullet 3. applies to all approaches allowing DHCPv4 leases. >> >> [ian] How so? If you have a 'wrapper' type of approach (where DHCPv4 is >>being put into IPv6 or DHCPv6), then the DHCPv4 over xv6 client function >>can be agnostic to what the physical interface is beyond 'it must >>support multicast or unicast'. If the DHCPv4oSW mechanism is not linked >>just to softwires and is essentially a 'vanilla' DHCPv4 client, then it >>must have awareness of the link layer capabilities of the link on which >>it is running and potentially adapt it's behaviour accordingly, such as >>per-client l4 port-restrictions. > >I read this bullet to be about the interface to be _provisioned_. >regardless of how that information reaches the client, the client must be >aware of the link-layer restrictions. and that I believe apply to all >mechanisms, regardless. > >> >>> bullet 4. please expand. >> >> [ian] This was from a question I asked on the ML some time ago, but >>wasn't answered. Does MAP-T support broadcasts through the translator >>function? > >I don't see why it wouldn't. [ian] OK, removed the con. > >>> bullet 5. change to "Restricted to a broadcast capable >>>link-layer." >> >> [ian] Is the hub-and-spoke restriction incorrect? As mentioned above, I >>don't see how this approach can work in a mesh environment. The >>'broadcast capable' restriction is not correct as if a h&s softwire can >>support broadcast, then a ptp mesh softwire can as well. You could >>broadcast DHCPDISCOVERs to peers in a mesh group, but it's not going to >>get you any response. > >MAP in mesh mode, still has a point to point tunnel to the BR. >we have not described MAP in a 'pure' mesh mode, i.e. without a BR. [ian] This document isn¹t meant to be limited to MAP mesh. E.g. RFC5565. > >>> 3.5.1 bullet 3. DHCPv4 and DHCPv6 cannot really be separated from each >>>other since it >>> it is DHCPv6 that provides transport for DHCPv4. and support >>>for the new BOOTP messages >>> are required in DHCPv6. >> >> [ian] But a dedicated DHCPv4 over DHCPv6 server could be deployed >>separate from the DHCPv6 only server. What about changing to read?: >> >> 'DHCPv4 and DHCPv6 based provisioning infrastructure can be seperated' > >as long as there is a DHCPv4 message capable DHCPv6 server. [ian] Sure. But if you didn¹t have a DHCPv4 capable server, then you wouldn¹t have sent the DHCPv4pDHCPv6 client the option to tell it to attempt DHCPv4oDHCPv6 configuration. >
- Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configur… ian.farrer
- Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configur… Ian Farrer
- [dhcwg] I-D Action: draft-ietf-dhc-v4configuratio… internet-drafts
- Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configur… Ian Farrer
- Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configur… Ole Troan
- Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configur… Ole Troan
- Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configur… Qi Sun
- Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configur… Ted Lemon
- Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configur… Qi Sun
- Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configur… Ole Troan
- Re: [dhcwg] I-D Action: draft-ietf-dhc-v4configur… Ole Troan