RE: [dhcwg] RFC2131 - option multiple times

Don't forget RFC 3396:

Abstract

   This document specifies the processing rules for Dynamic Host
   Configuration Protocol (DHCPv4) options that appear multiple times in
   the same message.  Multiple instances of the same option are
   generated when an option exceeds 255 octets in size (the maximum size
   of a single option) or when an option needs to be split apart in
   order to take advantage of DHCP option overloading.  When multiple
   instances of the same option appear in the options, file and/or sname
   fields in a DHCP packet, the contents of these options are
   concatenated together to form a single option prior to processing.

There are no hints in 2131/2 about which options may or may not be "split".

The bottom line is avoid splitting options unless you have an explicit need,
such as outlined above in the 3396 abstract.

- Bernie

> -----Original Message-----
> From: dhcwg-bounces@ietf.org [mailto:dhcwg-bounces@ietf.org] 
> On Behalf Of Grubmair Peter
> Sent: Friday, March 11, 2005 4:12 AM
> To: Dhcwg (dhcwg@ietf.org)
> Subject: [dhcwg] RFC2131 - option multiple times - which ones ?
> 
>  Hi,
> Thank you for your replies.
> My question was much simpler:
>  RFC2131 says:
> 
>    The values to be passed in an 'option' tag may be too long 
> to fit in
>    the 255 octets available to a single option (e.g., a list 
> of routers
>    in a 'router' option [21]).  Options may appear only once, unless
>    otherwise specified in the options document.  The client 
> concatenates
>    the values of multiple instances of the same option into a single
>    parameter list for configuration.
> 
> I interpreted it like this:
>   The rule is, that a specific option may appear only once in
>   a dhcp message.
>   The exception from this rule is, that the option document 
> (RFC2132 or
> other)
>   tells , that the option may appear multiple times.
>   Then the multiple instances of the option have to be 
> concatenated into
>   one instance before interpretation.
> 
>   So I am missing in RFC2131 hints, which option may appear 
> multiple times
> and
>   therefore have to be concatenated during reception(e.g. 
> router option ?)
> 
>   I think all options using charackter strings or lists (of 
> ip addresses)
> may
>   be split during send and have to be concatenated during reception
>  , but RFC2132 tells nothing about this.
> 
> Best regards
>   Peter
> 
>   
> 
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RE: [dhcwg] RFC2131 - option multiple times - which ones ?