[WG-BB] Study Report: CATV assignment guidline

[MAEMURA Akinori <maem@maem.org>]

Colleages,

WG-BB report was presented in the last Policy SIG in Taiwan.
We JPNIC IPwg reported it in JPNIC Open Policy Meeting but
there some SIers and CATV operators presented their opinion
around default bootstrap assignment size.

JPNIC IPwg had a meeting with concerned people and studied
this issue.  The Following is the study report.

As I asked Arano-san with a hat of chair of Policy SIG, I'd
like to present something based on this discussion, after 
discussing in this wg-bb.


Summary:
------------------------------------------------------------
  a)	Default assignment size should be considered upon
		"number of downstream port" and 
		"capacity specification" by the hardware,
	instead of simply number of CMTS.

  b)	In case of one 30Mbps type cable, /24 will typically
	last three months.  Considering it can connect 2,000
	users for example, it is never harmful if default 
	size for this is /23 which lasts six months.
------------------------------------------------------------
Discussions:

 1)	CMTS itself has various port density and capacity.
	some can connect multiple cables and there are two
	types of specifications which allow 10Mbps and 30Mbps.
	The difference of the capacity will be clearly 
	distinguished by product name.


 2)	some CMTS has a configuration with different numbers
	of upstream/downstream ports.  This is because down-
	stream cable can be divided into multiple with no
	significant signal loss but cable aggregation at up-
	stream cable will increase noise level so such a CMTS
	is designed to connect upsteam cables with no cable
	aggregators.

	Here the number of downsteam cables is the most 
	appropriate index for deciding default assignment 
	size if capacity specification is taken account into.


 3)	Maximum number of customers for a cable is suggested
	for each hardware for example 2,000 but the practical
	number will vary according to the design policy of
	each operator.


 4)	The proposed default assignment size that is a /24 
	for one CMTS is meets design condition of
	  a)	30Mbps type CMTS connecting one downstream
	  b)	Multiplexing late 1000%
	  c)	1Mbps throughput per user


 5)	Statistics of Cable Internet in Japan says average
	distributed capacity for one Cable Internet user is
	5Kbps to 12Kbps.  It corresponds ten times as many 
	customers as scenario in 4) while it is just an 
	avarage and it depends on service level design of 
	each operator.


 6)	Customer demand in the bootstrap phase of CATV 
	depends on its circumstances like existing xDSL 
	services in the area, IP awareness or someting like 
	these.  But /24 is likely to be a size that it lasts
	three months in bootstrap in a typical case.


 7)	In case of cisco hardware,  multiple secondary 
	addresses can be assigned to single cable interface
	so that Operator can easily add another assignment
	after it is implemented, however some hardwares do
	not allow this and single subnet must be assigned
	there.

------------------------------------------------------------



Regards,
Akinori
-
- This list (wg-bb) is handled by majordomo@lists.apnic.net