I've always thought that insistence on the use of RFC 2782 labels with SRV records unreasonably overconstrained the use of SRV records; and thus, limited their applicability.
Part of the problem, I suspect, is that at the time that 2782 was being drafted there may have been some belief that SRV records could reasonably be retroactively applied to all existing protocols, and thus there would be a need for a uniform syntax for DNS labels used with SRV records. But if (as is IMO appropriate) SRV records are only used with applications that are specified to use them, there is little benefit for the format of DNS labels used with SRV to be uniform across all uses of SRV. (I won't say "no benefit". A DNS API designed to facilitate easy SRV record lookup might benefit from a standard label syntax, but even then, it would make more sense to not embed that knowledge in the API and let the application construct the label to be queried.) So IMO all uses of SRV records should not be constrained to use RFC 2782 DNS labels. Keith On Sep 11, 2011, at 4:12 PM, Joe Touch wrote: > Hi, all, > > I've reviewed this document as part of the transport area directorate's > ongoing effort to review key IETF documents. These comments were written > primarily for the transport area directors, but are copied to the document's > authors for their information and to allow them to address any issues raised. > The authors should consider this review together with any other last-call > comments they receive. Please always CC tsv-...@ietf.org if you reply to or > forward this review. > > This document describes the use of DNS SRV records to coordinate NFS4 use and > a global file namespace across a groups of clients and servers. > > There are no transport protocol issues in this document. The key transport > issue is the definition of a new DNS SRV record and its associated syntax. > > There are issues with the intended syntax of the proposed DNS SRV record. The > current syntax is defined in RFC 2782 as: > > _service._transport.NAME > > service is an IANA SRV name, the namespace of which is defined in RFC > 6335 > > transport is _TCP or _UDP > > NAME is a DNS FQDN > > Given other considerations below (on versioning), the record should be one of > the following > > _nfs._tcp.example.com TTL Class SRV Priority Weight Port Target > _nfs._udp.example.com TTL Class SRV Priority Weight Port Target > > All other information specific to the exchange, e.g., organization (which may > or may not be a suffix of the Target, FWIW), desired mount point, and various > NFS-specific capabilities (e.g., mount options) ought to be expressed in an > associated TXT record as defined fields, as is the case with other services > that use SRV records. These options can have defaults if not otherwise > present. > > Some other issues are discussed below. > > Overall, the above is the key concern, and needs to be addressed before > proceeding. Issues below are indicated as either critical or suggestions for > clarification. > > Joe > > ------------------------ > > Critical issues: > > - the IANA section is incomplete > This document needs to request IANA assign an SRV service name, e.g.: > > SRV nfs TCP > SRV nfs UDP > > It is not clear whether an additional assignment of "SRV nfs SCTP" is > required; recent discussions on other SCTP SRV uses suggest that UDP is > indexed in these cases instead. This might warrant further discussion. > > - the service name should not include the version number > As per RFC 6335, and to be consistent with the existing port assignments for > NFS Version 4. > > - the discussion of list of organizations as with root.afs should be > described in a little more detail > The current sentence is a bit cryptic; this could be a full paragraph, > perhaps with an example. > > - there is no appropriate place to indicate write vs read-only in the DNS > request > The DNS request should return all available options, and indicate write vs. > read-only in the associated TXT records. The client should then determine > which is desired. > > ---------------------- > > Other issues (intended as suggestions): > > - version 4 > Throughout this document, "version 4" is used wherever NFS is used. Since V4 > (more specifically, 4.1) is the current common version, it does not seem > necessary to include this marking in most places except where differences in > the NFS versions are being highlighted. > > - colloquial advice > Terms like "appropriate" and "useful" should be removed throughout. They > represent judgements whose evaluation criteria is not discussed. > > - overall writing style > The document is written in the tense and style of a proposal. It should be > revised to read as the intended specification it will become. "We propose" > and "We use", and similar styles should be replaced with "this document > specifies" and "this record uses". > > - clarify overloaded terms > Terms like "root" and "name space" are widely used in different ways in the > DNS and file systems. Because this document combines the two, each use should > be clarified by a preceding term, e.g., DNS name space or file system name > space, DNS root or file system root. > > - the use of RFC 2119 terms should be reviewed > In particular, SHOULD should be used only where a specific exception is > currently known or suspected, and that exception described. This provides the > motivation for the selection of SHOULD vs. MAY or MUST. > > - the discussion of client vs server implementation (sec 4.3, as well as > partly in sec 4.2) should consider client-specific DNS responses > The DNS could provide responses that vary based on the IP of the client. This > could be a desirable feature. Further, the client knows whether it wants > write or read-write copies. AFAICT, the client is not only the better place > to implement this capability, it is the only viable place. > > - I found the hidden directory name discussion odd > It does not make sense to overload read-only with directory visibility; these > are orthogonal issues. The desired mount point should be indicated in the TXT > record; if a default convention is desired, it should be indicated in the > description of that field. > > - the AMD reference is only a web page > Not sure which particular reference is best, but a permanent reference would > be useful, e.g.: Matthew Crosby. 1997. AMD—AutoMount Daemon. Linux J. 1997, > 35es, Article 4 (March 1997). > > ----- > > > _______________________________________________ > Ietf mailing list > Ietf@ietf.org > https://www.ietf.org/mailman/listinfo/ietf _______________________________________________ Ietf mailing list Ietf@ietf.org https://www.ietf.org/mailman/listinfo/ietf
