Re: [dhcwg] rfc3679bis, or: about allocation of DHCPv4 options (was [IANA #1172829] Request for Early Allocation of DHCPv4 option (draft-ietf-dhc-v6only)

"Bernie Volz (volz)" <volz@cisco.com> Tue, 23 June 2020 22:09 UTC

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From: "Bernie Volz (volz)" <volz@cisco.com>
To: Michael Richardson <mcr+ietf@sandelman.ca>, "dhcwg@ietf.org" <dhcwg@ietf.org>
Thread-Topic: [dhcwg] rfc3679bis, or: about allocation of DHCPv4 options (was [IANA #1172829] Request for Early Allocation of DHCPv4 option (draft-ietf-dhc-v6only)
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Subject: Re: [dhcwg] rfc3679bis, or: about allocation of DHCPv4 options (was [IANA #1172829] Request for Early Allocation of DHCPv4 option (draft-ietf-dhc-v6only)
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Hi:

> As I read the RFC3679 recommendations, it seems that IANA was not actually following them.

>From RFC3678:

6. IANA Considerations

   IANA has returned the DHCP option codes listed in Section 2 to the
   list of available option codes.  These option codes may be reassigned
   to new DHCP options, according to the procedures in RFC 2939 [6].
   IANA is requested to reassign these option codes after the list of
   option codes that have never been assigned or have previously been
   returned has been exhausted.


I think they are trying to follow the last sentence. But this is just a request; it is on part of an IETF document requesting a specific value [provided that value is not actively assigned at the time IANA does the assignment].

And, 108 (section 2.10) falls into section 2 which is:

2. Unused DHCP Option Codes to be Reassigned to Future DHCP Options

   The option codes listed in this section are to be returned to IANA
   for reassignment to new options.  Responses from associated contact
   persons are noted where they have been received.

BTW: I did a google search for "dhcp option 108" and while it uncovered DHCPv6 option 108, there was no DHCPv4 option (things it found said this was undefined) - of course it also found RFC3678. While not authoritative, it does support the belief that this option is not in use as to use it would require some documentation to specify what it is and how to set it. I'm not sure how it was discovered back when Ralph worked on RFC3678 that is was "swap path". Include "swap path" in the google search turns up different hits, where some have defined it to be swap path. One interesting one is:

https://archive.org/stream/sg245280/sg245280_Beyond_DHCP_Work_Your_TCPIP_Internetwork_with_Dynamic_IP_djvu.txt (goes from START---- to ----END, pasted as it came):

START----

D.4 Unofficial DHCP options 

Several additional options, while not yet part of the official RFC 2132 
standard, have achieved some degree of popularity and are in common use. 
If you are interested in the latest inventory of unofficially assigned DHCP 
options, the list is available on the Internet at: 

ftp : //ftp . isi . edu/ in-notes/ iana/ assignments 



Appendix D. DHCP options (RFC 2132) 481 



Option 


Description 


62 


NetWare/I P Domain Name 


63 


NetWare/I P Suboptions 


77 


User Class 


78 


Directory Agent Information 


79 


Service Location Agent Scope 


80 


Naming Authority 


81 


Client Fully Qualified Domain Name 


82 


Agent Circuit ID 


83 


Agent Remote ID 


84 


Agent Subnet Mask 


85 


Novell Directory Services Servers 


86 


Novell Directory Services Tree Name 


87 


Novell Directory Services Context 


88 


IEEE 1003.1 POSIX Timezone 


89 


Fully Qualified Domain Name 


90 


Authentication 


91 


Banyan Vines TCP/IP Server 


92 


Server Selection 


93 


Client System Architecture 


94 


Client Network Device Interface 


95 


Lightweight Directory Access Protocol (LDAP) 


96 


IPv6 Transitions 


97 


UUID/GUID-based Client Identifier 


100 


Printer Name 


101 


Multicast Scope 


102 


Start Time 


103 


Multicast Time-to-Live 


104 


Multicast Block Size 


105 


Client Port 


106 


Cookie 


107 


Multicast Scope List 


108 


Swap Path 


109 


Autonomous System Number (ASN) 


110 


IPX Compatibility 


111 


Served IP Range 


112 


Netlnfo Parent Server Address 


113 


Netlnfo Parent Server Tag 


114 


Universal Resource Locator (URL) 


115 


DHCP Failover Protocol 


126 


Extension 


127 


Extension 


482 Beyond DHCP - Work Your TCP/IP Internetwork with Dynamic IP 




By convention, OS/2 Warp (and likely other IBM products) may use additional 
DHCP options in the 200 to 208 range. You may wish to use these same 
option numbers for the same purposes, even on non-IBM platforms. 

200 Default LPR Printer 

201 Default Gopher Server 

202 Default WWW Home Page 

203 Default WWW Proxy Gateway 

204 Default WWW News Server 

205 Default SOCKS Server 

206 NFS Mount Points 

207 Default X Font Servers 

208 X Display Manager Servers

----END

Which is a bit scary as we didn't have all of these.


But ... I think we are OK ... as:
1) They MAY be "reassigned" to new options.
2) IANA SHOULD reassigned only after "truly" unused option codes have been assigned. (Though of course, that is only as good as the information provided as to what an truly unused code is.)
3) But there's no harm in letting IETF documents request values that "MAY" be reassigned (see 1) .

- Bernie

-----Original Message-----
From: dhcwg <dhcwg-bounces@ietf.org> On Behalf Of Michael Richardson
Sent: Tuesday, June 23, 2020 5:06 PM
To: Bernie Volz (volz) <volz@cisco.com>om>; dhcwg@ietf.org
Subject: Re: [dhcwg] rfc3679bis, or: about allocation of DHCPv4 options (was [IANA #1172829] Request for Early Allocation of DHCPv4 option (draft-ietf-dhc-v6only)


Bernie Volz (volz) <volz@cisco.com> wrote:
    > I'm really not sure why this is generating so much discussion?

I think because many are surprised with the IANA interaction.

    > I do believe some had a bad experience with option 160, however, it was
    > related to Polycom usage. See

Yes, the question is whether there might be other submarine uses out there :-)

    > And, when we did the work to determine what was in use (~2004 if I
    > recall), no one ever reported that 160 had been used for anything so

Yes, I wasn't criticizing the work: it seems pretty clear to me.
I am just wondering if the results have just not sunk in enough.

    > So, can we be 100% certain there will not be an issues ... no. But that
    > applies to any value IANA may pick. And, we've probably now done more
    > to notify people of the use of 108 and so anyone that knows of a
    > concern would hopefully have stepped forward? Or perhaps may in the
    > next few days?

I doubt it: I think that if there was any use of 108 it's in places that can't spell IETF.

    > Note also that there have been other options allocated which have not
    > run into problems as far as I am aware.

Understood.

    > I don't think I would change the IANA recommendation, but I also see no
    > reason to disallow folks from recommending values if they have some
    > reason to do so.

As I read the RFC3679 recommendations, it seems that IANA was not actually following them.

--
Michael Richardson <mcr+IETF@sandelman.ca>ca>, Sandelman Software Works  -= IPv6 IoT consulting =-