Re: [Softwires] Working group last call for draft-ietf-softwire-map-dhcp-07

[Ian Farrer <[e-mail]>]

Hi Ole,

>> Old:
>> When receiving the Port Parameters option with an explicit PSID, the
>>  client MUST use this explicit PSID in configuring its MAP interface.
>>  If the conveyed IPv4 address is not 32 bit-long, the option MUST be
>>  discarded.  The formula for this check is "prefix4-len + ea-len = 32"
>>  and serves to ensure that the explicit PSID is only applied to
>>  configurations with a completely formed IPv4 address.
>> New:
>> On receipt of the Port Parameters option with an explicit PSID, clients
>>  MUST configure their softwire interface with the received
>>  explicit PSID. For MAP-E and MAP-T clients, if the conveyed IPv4 address
>>  is not 32 bits-long, the option MUST be discarded.  The formula for 
>>  this check is "prefix4-len + ea-len = 32" and serves to ensure that 
>>  the explicit PSID is only applied to configurations with a completely
>>  formed IPv4 address.
> 
> what about keeping the old text with your change of s/MAP interface/softwire interface/.
> at least in theory LW46 could support IPv4 prefixes, or a new mechanism could come along that did.
> 

[ian] Actually, looking at this again, the original text isn’t particularly clear. It talks about provisioning ports sets, and then makes a leap to the length of the IPv4 address, which is not conveyed in this option. Also, the 32 bit address checking logic is MAP specific. So:

When receiving the Port Parameters option with an explicit PSID, the
 client MUST use this explicit PSID in configuring its softwire interface.
 If the client’s IPv4 address (configured via a separate sub-option) 
 is not 32 bit-long, the Port Parameters option MUST be discarded.  
For MAP-E and MAP-T clients, the formula for the address length check
is "prefix4-len + ea-len = 32” and serves to ensure that  the explicit
PSID is only applied to configurations with a completely formed IPv4 address.

Cheers,
Ian