RE: [dhcwg] DHCP Option for CableLabs Client Configuration

["Sumanth Channabasappa" <[e-mail]>]

Hi,


	[Cosmo, Patrick] The CM must be completely provisioned before the MTA can (successfully) do DHCP, correct? So why can't you send the sub-option 1/2 data to the CM in its config file or through SNMP, and then let it pass it along to the MTA? 
	[sumanth] Not sure if I can answer this - there were various possible ways of doing it, however, changing the DOCSIS spec was not a sought after option and we had a suboption being introduced for PCBL which could be easily re-used with minimal changes. Besides it was not necessary to 'protect this info' as we havent addressed DHCP security.
	 
	 
	You want to ensure that the MTA gets a list of "legal telephony DHCP server addresses". This implies that without opts 1/2, the MTA may get DHCP from a server outside this list. Can anyone say whether there is a mechanism that ensures the CM only gets DHCP from valid servers (does the CMTS ensure this?)? This question has already been posited to Richard Woundy, but perhaps someone else knows? You can't protect the MTA from bogus DHCP servers, if you are trying to do it using data, forwarded from a CM, that originates from those same bogus DHCP servers. Similarly, this opt 1/2 mechanism does not allow the access provider to gain tighter control over its DHCP/DNS infrastructure if the CM can get DHCP from servers outside this infrastructure.
	 
	[sumanth] I guess Rich answered the Q on DHCP servers.
	 
	However, in case of Packetcable the architecture kept in mind that there could potentially be 'different' data and telephony service providers' using the same 'embedded' device ( EMTA ). This would mean that the 'data service provider' and the 'telephony service provider' could use different 'backoffice components' - which means that valid DHCP servers can
	still affect each others n/w - given that the MTAs come from behind the same MTA and mostly recognised as 'CPEs'
	- meaning multiple DHCP servers might have the same scopes.
	 
	To avoid any such scenarios it is advisable to let the MTA know which servers it could accept the OFFERs from and
	ofcourse you can have values like 255.255.255.255 if it does not apply.
	( Ofcourse, there are other ways to accomplish the same - this was what was chosen ). 
	 
	regards
	Sumanth