Subject: [ipcdn] Aging out docsSubMgtCpeIpTable entries

From: "ian wheelock" <[email-masked]>
Date: Fri, 4 Apr 2003 19:06:07 +0100

Hi

can entries in the docsSubMgtCpeIpTable ever be 'aged' out ?

the draft states 

   "The learning mechanism is not defined by this document.",

it does not state anything about the duration an entry is retained 
in the table or how/if "aging" should be part of the table operation.

the draft also states  

  "In particular, this MIB provides two capabilities: first, to limit
   the IP addresses behind a modem, and, second, to provide protocol
   filtering to and from a modem."

does the first capability suggest  
1/ limiting the 'number' of ip addresses,  OR
2/ limiting the 'specific' ip addresses (learned on a first-come basis, 
and once learned will NEVER be removed unless the table is reset) ?

if it is suggesting 1, then would 'aging' be acceptable ?

'aging' would enable new/different IP addresses to replace old/aged out 
'learned' IP addresses, while continuing to support the limiting of the 
number of IP addresses to the configured maximum (docsSubMgtCpeControlMaxCpeIp). 

Supporting aging would require an additional mib variable to be able to 
configure/read the aging interval.

i realise that there is a 'reset' option to clear out all 'learned' addresses.

Ian
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---

From: [email-masked]
Date: Fri, 4 Apr 2003 13:21:49 -0500

The short answer is 'yes', entries can be aged out.

We avoided specifying the learning mechanism because we wanted to leave it
open to a variety of mechanisms likely to already be part of the forwarding
process of CMTSs - for example, the ARP cache, bridge learning, DHCP
gleaning, etc. I'd think that the same rationale would apply to aging -
whatever replacement mechanisms and aging are part of CMTS forwarding table
maintenance could also be applied to the CpeIpTable.

The goal of the CpeIpTable is to prevent address spoofing. Any
aging/replacement process that is reasonably long duration (minutes) should
fulfill this purpose. Keep in mind, too, that the subscriber can always
clear the table by re-registering the modem.

- Wilson Sawyer

                      "ian wheelock"                                                                                                
                      <[email-masked]>          To:       <[email-masked]>                                                           
                      Sent by:                 cc:                                                                                  
                      ipcdn-admin@ietf.        Subject:  [ipcdn] Aging out docsSubMgtCpeIpTable entries                             
                      org                                                                                                           

                      04/04/03 01:06 PM                                                                                             

Hi

the draft states

the draft also states

'aging' would enable new/different IP addresses to replace old/aged out
'learned' IP addresses, while continuing to support the limiting of the
number of IP addresses to the configured maximum
(docsSubMgtCpeControlMaxCpeIp).

i realise that there is a 'reset' option to clear out all 'learned'
addresses.

Ian

---

From: "Woundy, Richard" <[email-masked]>
Date: Fri, 4 Apr 2003 12:25:58 -0700

Consider the following example of CMTS management of the CPE entries. If a
particular CPE with IP address 24.1.1.1 is renumbered (via DHCP) to IP
address 24.2.2.2, then it makes a lot of sense for the CMTS to replace the
24.1.1.1 entry with a 24.2.2.2 entry in the CPE table.

The example above shows a key motivation of why I don't see value in an
explicit "aging timer" MIB object. The CPE entry invalidation may be based
on DHCP gleaning by the CMTS -- and the DHCP messages are driven by timers
in the DHCP client (CPE) and DHCP server, not the CMTS.

-- Rich

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
Sent: Friday, April 04, 2003 1:22 PM
To: ian wheelock
Cc: [email-masked]
Subject: Re: [ipcdn] Aging out docsSubMgtCpeIpTable entries

- Wilson Sawyer

                      "ian wheelock"

                      Sent by:                 cc:

                      ipcdn-admin@ietf.        Subject:  [ipcdn] Aging out
docsSubMgtCpeIpTable entries                             
                      org

                      04/04/03 01:06 PM

Hi

the draft states

the draft also states

Ian