DOCSIS Mini-PIM Interface Overview
This section includes the following topics:
Introduction
Data over Cable Service Interface Specifications (DOCSIS) define the communications and operation support interface requirements for a data-over-cable system. DOCSIS is used by cable operators to provide Internet access over their existing cable infrastructure for both residential and business customers. DOCSIS 3.0 is the latest interface standard allowing channel bonding to deliver speeds higher than 100 Mbps throughput in either direction, far surpassing other WAN technologies such as T1/E1, ADSL2+, ISDN, and DS3.
DOCSIS network architecture includes a cable modem on SRX Series Services Gateways with a DOCSIS Mini-Physical Interface Module (Mini-PIM) located at customer premises and a cable modem termination system (CMTS) located at the head-end or data center locations. Standards-based DOCSIS 3.0 Mini-PIM is interoperable with CMTS equipments. The DOCSIS Mini-PIM provides backward compatibility with CMTS equipment based on the following standards:
- DOCSIS 2.0
- DOCSIS 1.1
- DOCSIS 1.0
DOCSIS Mini-PIM is supported on SRX210 and SRX240 Services Gateways.
Software Features Supported on DOCSIS Mini-PIMs
Table 15 lists the software features related to DOCSIS Mini-PIMs.
Table 15: Software Features Supported on DOCSIS Mini-PIMs
Term | Definition |
|---|---|
DHCP and DHCPv6 Clients | DHCP and DHCPv6 clients are used to get the IP address from the CMTS by using DHCP protocol. DHCP is supported on IPv4 and IPv6. One of the main components of the configuration file is the static public IP address, which CMTS assigns to the cable modem. The management IP address is configured on the Mini-PIM’s hybrid fiber coaxial (HFC) interface, which performs the following tasks:
|
QoS Support | The SRX Series device Routing Engine is configured through the existing QoS CLI. Because the configuration on the SRX Series device Routing Engine and Mini-PIM is done together, the QoS configuration has to be consistent between the SRX Series Routing Engine and the cable modem interface. The QoS mechanisms on the SRX Series Routing Engine are decoupled from the QoS mechanisms on the Mini-PIM. The configuration file downloaded from CMTS contains parameters for primary and secondary flows. These parameters are programmed in the DOCSIS Mini-PIM. The Mini-PIM sends these parameters to the SRX Series Routing Engine through the PIM infrastructure. The secondary flows are prioritized over primary flows in the DOCSIS Mini-PIM. |
SNMP Support | The SNMP requests are issued by CMTS and go to the cable modem. The DOCSIS MIB on the SRX Series device Routing Engine displays the Ethernet interface of the cable modem. The following features are supported on the DOCSIS Mini-PIM:
|
MAC Address | The MAC address of the DOCSIS Mini-PIM is statically set at the factory and cannot be changed. The MAC address is retrieved from the Mini-PIM and assigned to the cable modem interface in the JUNOS Software. |
Transparent Bridging | The DOCSIS Mini-PIM performs transparent bridging by sending the packets received on the Ethernet interface with the SRX Series device to the HFC interface and vice versa, without any modifications to the packet. All the other services such as Web server, DHCP server, and DNS server are disabled on the DOCSIS Mini-PIM during transparent bridging. |
Configuring DOCSIS Mini-PIM
The cable modem interface of Mini-PIM is managed and monitored by CMTS through SNMP. This DOCSIS 3.0 Mini-PIM can be deployed in any multiple service operator (MSO) networks. The primary application is for distributed enterprise offices to connect to a CMTS network through the DOCSIS 3.0 (backward compatible to 2.0, 1.1, and 1.0) interface. The DOCSIS Mini-PIM uses PIM infrastructure developed for third-party PIMs.
The Mini-PIM can also be used with encapsulations other than GRE, PPPoE, and IP-in-IP.
Figure 10 illustrates a typical use of this Mini-PIM in a multiple service operator (MSO) network.
Figure 10: Typical DOCSIS End-to-End Connectivity and Topology Diagram
