IP Assignment Procedure for Cable Modem & ADSL Yi Lee Seednet 90/06/13

Two-way Cable Modem As per DOCSIS standards, Two-way cable modem must obtain one IP by DHCP to finish the registration CPE obtains one IP by DHCP in order to access Internet ==>One subscriber needs at least 2 IPs to utilize the cable internet service

Telco-Return Cable Modem Telco-return Cable Modem needs 2 IPs to get on-line, one for its RF interface and the other for its PPP interface CPE needs 1 IP to access Internet ==>One telco-return subscriber needs at least 3 IPs to get on-line

Current Practice (Cable Modem) Private IP is assigned to each cable modem’s RF interface Due to common share of RAS by telco- return subscribers and dial-up subscribers, 1 public IP is assigned to each telco-return CM’s PPP interface In both cases(two-way and telco-return), CPE is assigned 1 public IP

Current Practice (cont.) Each CMTS is assigned /24 in the “bootstrap” stage for ease of management Another /24 is assigned to the CMTS if IP utilization is over 80% Seednet keeps track of subscriber’s usage record for at least 6 months due to the requirement of law enforcement agency in Taiwan

ADSL 3 different service types in terms of IP usage are supported by current ADSL technologies Dynamic IP -- Subscriber is assigned 1 IP when on line and releases it when off line, suitable for residential users. 1 static IP -- Subscriber is assigned 1 static IP, suitable for SOHO or professional users.

ADSL (cont) Fixed IP Block -- Subscriber is assigned a block of IP (/27 or more), suitable for business users.

Current Practice (ADSL) Residential subscriber is assigned 1 dynamic IP by PPPoE with ATU-R running in the bridge mode. Professional subscriber is assigned 1 static IP with ATU-R running in the bridge mode Business subscriber is assigned 8 static IPs (/29) with ATU-R running in the router mode

Current Practice (ADSL) Supporting information like 073 form and purchase receipt is required for business subscriber applying for /28 or /27.

Issues It‘s difficult for ISP to project the IP address consumption The usage pattern generated by users is different ADSL/Two-way cable users are always on-line Telco-return cable users are quite similar with dial-up users in that they tend to be off-line after finishing internet activities.

Issues (cont) It’s more common for a residential subscriber to have more than one CPE More PPPoE or DHCP sessions are requested per subscriber More leased-line users switch to ADSL but want to keep the IP blocks previously assigned from lease-line.

Issues (cont) Publishing residential user information onto the Whois database put ISPs into the risk of violating the privacy law

Any Question?