Table of Contents

Cisco IOS Software Release Feature Sets

Base IP (DOCSIS-Compliant) Bridging
Home Office (Easy IP)

Feature Descriptions

Cable Monitor Web Diagnostics Tool
DOCSIS-Compliant Bridging
DOCSIS Baseline Privacy Interface
DHCP Server
IP Address Negotiation
Network Address Translation and Port Address Translation
Quality of Service
Quality of Service---DOCSIS 1.0+ Extensions
Routing Information Protocol Version 2
Secure Shell Version 1

Initial Provisioning

Overview

This chapter provides a basic understanding of the software feature sets for the Cisco uBR910 series cable data service unit (DSU). This manual also describes the processes used for provisioning the Cisco uBR910 series DSU within a cable network and configuring it for different services.

This chapter contains the following sections:

• Cisco IOS Software Release Feature Sets

• Initial Provisioning

Note The Cisco uBR910 series includes the Cisco uBR914 DSU.

Cisco IOS Software Release Feature Sets

This section describes the common feature sets supported by the Cisco uBR910 series DSU. Each feature set contains a number of features that provide a specific functionality, such as the Easy IP feature set.

• Base IP (DOCSIS-Compliant) Bridging---Provides a high-speed connection to the Internet, using the standards in the Data Over Cable Service Interface Specification (DOCSIS). This feature set is included in all software images that are available for the Cisco uBR910 series DSU.

• Home Office (Easy IP)---Provides a high-speed connection to the Internet, along with server functions that simplify the administration of IP addresses. In addition to simplifying network management, this allows the Cisco uBR910 series DSU to connect a small number of computers to the Internet through the cable interface. This is the default software image for the Cisco uBR910 series DSU.

The following sections describe each feature set in more detail.

Note This manual describes the Cisco uBR910 series DSU and feature sets as they exist in Cisco IOS Release 12.1(3)T.

Base IP (DOCSIS-Compliant) Bridging

The Base IP Bridging feature set includes DOCSIS-compliant bridging and DOCSIS Baseline Privacy Interface (BPI) encryption. It allows the Cisco uBR910 series DSU to function as a cable modem that can interoperate with any DOCSIS-qualified Cable Modem Termination System (CMTS).

Note The Base IP (DOCSIS-compliant) Bridging feature set exists in all software images for the Cisco uBR910 series DSU.

DOCSIS-compliant bridging (also referred to as "plug-and-play" bridging) is the default configuration for the Cisco uBR910 series DSU. In this mode, the Cisco uBR910 series DSU automatically does the following at power-on and system reset:

• Acquires temporary downstream and upstream channels

• Finds the appropriate Time of Day (ToD), Trivial File Transfer Protocol (TFTP), and Dynamic Host Configuration Protocol (DHCP) servers

• Obtains the current time of day from the ToD server

• Obtains an IP address from the DHCP server

• Downloads a DOCSIS configuration file from the TFTP server

• Configures itself for its permanent downstream and upstream channels

• Obtains other DHCP parameters to work in bridging mode

• Downloads a Cisco IOS image and Cisco IOS configuration file (if specified in the DOCSIS configuration file)

• Establishes a BPI session (if enabled on both the Cisco uBR910 series DSU and CMTS)

When in DOCSIS-compliant bridging mode, the Cisco uBR910 series DSU acts as a transparent IP bridge for the PCs on the customer's local area network (LAN). In this mode, IP traffic is bridged between the Cisco uBR910 series serial and cable interfaces; the cable provider can optionally maintain the IP addressing of the PCs on the customer's LAN.

Note A maximum of 254 CPE devices are supported when both the Cisco uBR910 series DSU and access router are operating in bridging mode. The actual number of CPE devices also depends on the value of the "MAX CPE" field in the DOCSIS configuration file. The MAX CPE field defaults to one CPE device unless set otherwise. The number of CPE devices is not limited when either the Cisco uBR910 series DSU or access router is operating in IP routing mode.

Home Office (Easy IP)

The Home Office feature set provides high-speed Internet connectivity for customers who have a small home network. In addition to DOCSIS-compliant bridging, the Home Office feature set provides the Easy IP set of features that simplifies the administration of IP addresses in a cable network. This feature set supports intelligent DHCP Server functions, such as DHCP Relay Agent and DHCP Client functionality. It also supports Network Address Translation and Port Address Translation.

The DHCP features provide intelligence and flexibility in the handling and distribution of IP addresses for the PCs and other CPEs being connected to the cable network. The NAT/PAT features allow the customer to use private IP addresses on the local network, while still maintaining connectivity to the Internet.

Feature Descriptions

This section describes the particular features that are contained in the feature sets supported by the Cisco uBR910 series DSU. See the release notes for a particular release for information on which features are contained in a particular Cisco IOS image.

Cable Monitor Web Diagnostics Tool

The Cable Monitor is a web-based diagnostic tool to display the current status and configuration of the Cisco uBR910 series DSU. The Cable Monitor can also be used when the cable network is down, providing an easy way for subscribers to provide necessary information to service technicians and troubleshooters.

DOCSIS-Compliant Bridging

DOCSIS-compliant bridging allows the Cisco uBR910 series DSU to operate as a DOCSIS 1.0 cable modem, so that it can interoperate with any DOCSIS-qualified CMTS. This is the default mode of operation for the Cisco uBR910 series DSU.

DOCSIS Baseline Privacy Interface

The DOCSIS Baseline Privacy Interface (BPI) feature is based on the DOCSIS BPI Specification (SP-BPI-I02-990319 or later revision). It provides data privacy across the hybrid fiber-coaxial (HFC) network by encrypting traffic flows between the Cisco uBR910 series DSU and the cable operator's CMTS.

The BPI+ (BPI Plus) feature is an enhancement to the BPI feature and is based on the DOCSIS BPI+ Specification (SP-BPI+-I04-000407 or later revision), which is still in development. In addition to the regular BPI features, BPI+ provides more secure authentication of cable modems through the use of digital certificates. Also, a cable modem can use a digital signature to verify that the software image it has downloaded has not been altered or corrupted in transit.

Note The CMTS and Cisco uBR910 series DSU must both support and enable BPI+ to use its features. If the CMTS does not support BPI+, the Cisco uBR910 series DSU defaults to using standard BPI.

DHCP Server

The DHCP server feature on the Cisco uBR910 series DSU includes both Intelligent DHCP relay and DHCP Client functionality. A DHCP relay agent is any host that forwards DHCP packets between clients and servers---this enables the client and server to reside on separate subnets. If the Cisco uBR910 series DHCP server cannot satisfy a DHCP request from its own database, it can also act as a DHCP proxy agent by forwarding the DHCP request to one or more secondary DHCP servers.

IP Address Negotiation

Cisco IOS Release 12.1(3)T for the Cisco uBR910 series DSU adds support for the ip address dhcp command on the cable interface. Previous releases used the ip address negotiated command for this purpose, but this command is now reserved for serial interfaces.

Network Address Translation and Port Address Translation

Network Address Translation (NAT) and Port Address Translation (PAT) frees a private network from needing a worldwide unique IP address for every computer connected to the Internet. Instead, the Cisco uBR910 series DSU translates the IP addresses used on the private network into a global IP address that can be used on the Internet. One IP address can be used for multiple computers because a unique port address identifies the individual computers on the private network.

Note NAT and PAT are defined in Requests for Comments (RFC) 1631 .

Quality of Service

Quality of service (QoS) is a set of features that identify different types of traffic on a network so that certain types of traffic can be given higher priority than traffic that has only a "best effort" attempt at delivery. This feature is especially important for real-time traffic, such as voice traffic, where delays would have a serious impact on the traffic's usefulness.

Depending on the software image used, the Cisco uBR910 series DSU supports the following QoS features:

• Resource Reservation Protocol (RSVP)---Layer 3 QoS signaling protocol that provides for the reservation of resources across an IP network. Applications running on IP end systems can use RSVP to indicate to other nodes the nature (such as bandwidth, jitter, and maximum burst) of the packet streams they want to receive. RSVP is defined in R FC 2205.

• Committed Access Rate (CAR)---Specifies the minimum bandwidth that is guaranteed for a particular type of traffic.

• Multi-Service Identifier (SID)---Allows a service provider to offer different classes of service to its customers, so that different types of traffic can be given different priorities of service.

• Traffic Shaping---Process of delaying packets that would otherwise be dropped because they exceed the rate limit on a particular cable modem's upstream. The Cisco uBR910 series DSU buffers the upstream packet until bandwidth is available. This is particularly important with TCP/IP traffic because when a TCP packet is dropped, the destination device automatically drops all other packets it currently contains in its receive buffer and then requests the retransmission of those packets. This retransmission of packets increases the congestion that already exists in this situation, drastically reducing overall throughput. Traffic shaping helps avoid this retransmission of packets.

Quality of Service---DOCSIS 1.0+ Extensions

In addition to the other QoS features, DOCSIS 1.1 supports a number of features that are required for the reliable delivery of high-quality voice traffic. To use these features before the DOCSIS 1.1 specification is finalized, Cisco has created the DOCSIS 1.0+ extensions that contain the most important of these features.

• Concatenation---DOCSIS concatenation combines multiple upstream packets into one packet to reduce packet overhead and overall latency, as well as increase transmission efficiency. Using concatenation, a DOCSIS cable modem makes only one bandwidth request for multiple packets, as opposed to making a different bandwidth request for each individual packet; this technique is especially effective for bursty, real-time traffic, such as voice calls.

• Dynamic Multi-SID Assignment---To give higher priority to different traffic flows, the Cisco uBR910 series DSU can assign a different SID to each flow. Without the DOCSIS 1.0+ extensions, the DSU must create these SIDs during the provisioning process, and the SIDs remain in effect until the DSU is rebooted with a different configuration. To make sure that each SID has sufficient bandwidth for its needs, a minimum guaranteed bandwidth is permanently allocated to these SIDs; this bandwidth remains reserved even when not used.

To avoid wasting bandwidth in this manner, the DOCSIS 1.0+ extensions support the dynamic creation of multiple SIDs. New MAC messages dynamically add, modify, and delete SIDs when needed. When a SID is deleted, it automatically releases its allocated bandwidth, so that this bandwidth can be used by other traffic.

Note Both the Cisco uBR910 series DSU and the CMTS router must support the dynamic multi-SID and concatenation features for them to be used on the cable network. If using the Cisco uBR7200 series universal broadband router as the CMTS, Cisco IOS Release 12.0(7)XR or 12.1(1)T (or later revisions) is required to use these features.

Routing Information Protocol Version 2

When configured for routing mode, the Cisco uBR910 series DSU supports the Routing Information Protocol Version 2 (RIPv2). In routing mode, the Cisco uBR910 series DSU automatically configures itself to use the headend's IP address as its IP default gateway. This allows the Cisco uBR910 series DSU to send packets not intended for the private LAN to the headend for delivery to the Internet and other networks.

RIPv2 routing is useful for small internetworks because it optimizes Network Interface Center (NIC)-assigned IP addresses by defining Variable-Length Subnet Masks (VLSMs) for network addresses, and it allows Classless Interdomain Routing (CIDR) addressing.

Note The Cisco uBR910 series DSU supports only static routes and the RIP routing protocol.

Secure Shell Version 1

The Cisco uBR910 series DSU supports the Secure Shell (SSH) Version 1 protocol, which allows network administrators to make a secure Telnet connection with the Cisco uBR910 series DSU. SSH provides for authentication and encryption at the application layer, providing a secure connection even when BPI or IPSec authentication and encryption are not used at the network layer.

By default, the SSH feature uses 56-bit DES encryption. If the Cisco IOS image supports the 168-bit 3DES feature set, SSH also supports using the higher security 3DES encryption. (The SSH server and client must support the same level of encryption.)

SSH server support for the Cisco uBR910 series DSU is introduced in Cisco IOS Release 12.1(1)XD. SSH client support is introduced in Cisco IOS Release 12.1(3)T.

Note For configuration and other information, see the Secure Shell Version 1 Client feature module, available on CCO and the Documentation CD-ROM.

Initial Provisioning

The Cisco uBR910 series DSU typically ships from the Cisco factory ready to work in the Base IP (DOCSIS-Compliant) Bridging mode. However, before the Cisco uBR910 series DSU can transmit traffic, the CMTS at the headend must properly provision the Cisco uBR910 series DSU as follows:

• The appropriate service must be purchased from the service provider. If necessary, a license for the appropriate Cisco IOS software image must also be purchased.

• The service provider must create a DOCSIS configuration file for the Cisco uBR910 series DSU. This file must be stored on a TFTP server---each Cisco uBR910 series DSU could have its own unique DOCSIS configuration file, or the same file could be used for multiple systems, depending on the needs of the subscribers.

• When the Cisco uBR910 series DSU is first brought online, the CMTS at the headend downloads the DOCSIS configuration file to the Cisco uBR910 series DSU. This file is a binary file that configures the Cisco uBR910 series DSU for the appropriate level of services and that sets other parameters for cable operations.

• At this point, the Cisco uBR910 series DSU is completely configured for basic DOCSIS bridging, but when additional features are required, the DOCSIS configuration file specifies that the CMTS should download a second Cisco IOS image to the Cisco uBR910 series DSU.

• Finally, any additional configuration on the Cisco uBR910 series DSU must be done. At the minimum, the serial interface on the Cisco uBR910 series DSU must be configured with the proper parameters. This can be done in the following ways:

  • Enter the appropriate CLI commands into the Vendor Specific Information Field (using option 131) in the DOCSIS configuration file.

  • The Cisco uBR910 series DSU can download a Cisco IOS configuration file from a host workstation specified by the DOCSIS configuration file. The Cisco IOS configuration file is an ASCII text file that contains the Cisco IOS commands needed to configure the Cisco uBR910 series DSU for routing operations across the serial interface.

  • A system administrator can manually configure the Cisco uBR910 series DSU by giving Cisco IOS commands at the CLI interface. This can be done either locally by connecting to the RJ-45 console port or remotely by establishing a Telnet connection with the system.

Note The CMTS typically downloads the DOCSIS configuration file, Cisco IOS image (if needed), and Cisco IOS configuration file (if needed) only once when the system is initially brought online. However, a new configuration file or image can be downloaded whenever necessary, such as when the cable service offers new services or when subscribers upgrade their services.

To ensure that subscribers obtain the exact services they have ordered, the Cisco uBR910 series DSU has a unique identifier (UID) that consists of a serial number as well as the media access control (MAC) address that is assigned to the cable interface. These factory-assigned values are on a label at the bottom of the chassis for convenience, these values are also in a barcode label that can be scanned in for easy entry into the service provider's provisioning and billing system.

Using the MAC address of the Cisco uBR910 series DSU as the key, the CMTS downloads the DOCSIS configuration file and Cisco IOS image that will provide the services this particular subscriber has purchased. Service technicians at the headend typically create a number of standard configuration files to match the range of services offered by the provider; these configuration files can be created manually or with tools that Cisco Systems provides for this purpose.

Note For a more detailed description of the provisioning process, see the Cisco uBR910 Series Hardware Installation Guide, available on CCO and the Documentation CD-ROM.

Posted: Fri Jul 21 12:34:34 PDT 2000
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