KR20030048475A - Robust method and apparatus for processing cable modem configuration files - Google Patents

Abstract

An apparatus for processing simple network management protocol object identifiers in a network management file. Objects are classified according to scalar or table values, and further classified according to the number of digits in each object identifier and the number of unequal values within the digits. Packet data units are then created by integrating similar object types. Each packet data unit is processed separately. By categorizing and processing SNMP objects first, the effects of faulty or invalid objects in network management processing are minimized.

Description

Robust method and apparatus for processing cable modem configuration files

Internet access through a telephone modem is available today at speeds up to 56 Kbps. A telephone based modem modulates and demodulates data signals for transmission over a voice band telephone network. In contrast, cable modems provide Internet access through cable television systems that provide higher bandwidth and thus operate at higher data rates than telephone systems. The cable modem provides a connection between the user's computer or other communication device and the cable system headend from which access to the Internet or other external network is available, for example, via a T1 transmission line. In a cable network, data transmitted from the network headend to the user or subscriber is called downstream data, and data transmitted from the user to the network headend is called upstream data.

An exemplary prior art bidirectional cable system is shown in block diagram form in FIG. 1. Prior art cable systems include a headend device 101, a hybrid fiber coaxial (HFC) cable plant 103, a plurality of cable modems 105 and 106 (only two are shown), and corresponding communication links. Corresponding subscriber terminals 107 and 108 (only two are shown) connected to cable modems 105 and 106 via devices 116 and 117. Exemplary communication devices 107 and 108 include a computer, television or telephone. As is well known, the headend device 101 may include processors, routers, switches, broadband downstream transmitters, upstream receivers, distributors, combiners, subscriber databases, network management stations, dynamic host setup communications. Dynamic host configuration protocol (DHCP) and trivial file transfer protocol (TFTP) servers, call agents, media gateways, and tolling systems. The HFC cable plant 103 transmits through the shared downstream channel 110 from the headend device 101 to the cable modems 105 and 106, and the headend device (c) in the cable modems 105 and 106. Fiber optic cables, coaxial cables, fiber / coaxial nodes, amplifiers, filters, and taps that support transmissions over shared upstream channel 112 to 101. As discussed below, program signals are input to the headend device 101 as shown for broadcast to cable subscribers.

Each channel 110 and 112 may use different transport protocols to convey information. Typically, the modulation used to convey information over the downstream channel 110 (eg, quadrature amplitude modulation (QAM)) is used to convey information over the upstream channel 112. Higher order downstream than the upstream transmissions and higher order than the modulation used (e.g., differential quadrature phase shift keying (DQPSK) or hexadecimal QAM) To get them as a result. Cable systems where upstream transmission rates are slower than downstream transmission rates are typically referred to as "asymmetric" systems. Cable systems where upstream transmission rates are substantially equivalent to downstream transmission rates are typically referred to as "symmetric" systems.

In addition to the specific type of modulation used for each channel 110 and 112, the shared attributes of each channel 110 and 112 include other protocol requirements. For example, because the downstream channel 110 is shared, the downstream protocol includes address information, and each cable modem 105 and 106 monitors the downstream channel 110 for information packets addressed thereto. Addressed to a particular cable modem 105 or 106 (or attached communication devices 107 or 108) or to all cable modems 105 or 106 (or attached communication devices 107 or 108) Only the information packets (e.g., broadcast messages) that have been processed are processed by the cable modems 105 and 106 and, as appropriate, transmitted to the associated subscriber communication devices 107 and 108. Since the upstream channel 112 is shared, the upstream channel access protocol is designed to reduce the likelihood of collisions of conveyed information coming from the cable modems 105 and 106. Multiple multiple access protocols include ALOHA, slot-ALOHA, come division multiple access (CDMA), time division multiple access (TDMA), collision detection TDMA, and carrier sense multiple access (CSMA) It includes well known protocols such as sense multiple access, and exists to define upstream channel access.

Some bidirectional cable systems conform to and use the upstream and downstream channel protocols defined in the recently published standard heading, Data-Over-Cable System Interface Specification (DOCSIS) Version 1.0. The upstream protocol defined by the DOCSIS standard is that timing is controlled by the headend device 101 (called a cable modem termination station (CMTS) in DOCSIS) and the downstream channel 110 It is a TDMA scheme delivered to the cable modems 105 and 106 via time stamp synchronization messages transmitted via SMB. Thus, in order to generate upstream communication in turn, in a high quality manner, the time reference of each cable modem 105 and 106 is based on the information provided by the modems 105 and 106 by the subscriber communication devices 107 and 108. Before starting the transmission, it should be substantially synchronized with a similar time reference of the headend device 101. Without proper synchronization, transmissions from one modem 105 may conflict with transmissions from another modem 106.

The headend device 101 is typically a public switched telephone network (PSTN) via an appropriate communication link 119, such as a fiber distributed data interface (FDDI) link or a 100 baseT Ethernet link. A wide area packetized network, such as an external network 114 or the Internet. Thus, the bidirectional cable system provides a communication connection between subscriber communication devices 107 and 108 (and other similar devices not shown in FIG. 1) and Internet servers on external network 114, computer networks, and the like. .

2 is a block diagram of cable components at a user or subscriber site, including cable modem 105. In the subscriber's premises, the distributor 134 distributes the incoming signal so that the program signal is displayed on the television 140 under the control of the set top box 138. A second output terminal at distributor 134 provides a connection to cable modem 105. Downstream signals from the HFC cable plant 103 are supplied to a radio frequency (RF) tuner 142, which is assigned to the cable modem 105 during the modem's start-up phase. Tuned to frequency. The downstream signal is demodulated in demodulator 144, and the output therefrom is input to media access controller 146. The signal from the media access controller 146 is input to the data and control logic unit 148 that controls the overall operation of the cable modem 105 and further provides data control and allocation functions.

The communication device 108 is configured to receive data transmitted in the downstream direction from the HFC cable plant 103 and typically to transmit the data in the upstream direction to the final destination of the external network 114. The data and control logic unit 148 of the modem 105 is connected. Data exiting from communication device 108 is passed through data and control logic unit 148, through media access controller 146, and finally modulated by modulator 150. The upstream data is then passed through distributor 134 for transmission to HFC cable plant 103.

Referring back to FIG. 1, the headend device 101 may transmit program signals (satellite downlink, terrestrial microwaves or land lines) for broadcast to the communication devices 107 and 108 via the cable modems 105 and 106, respectively. Also via landlines). The program signals are carried over the 6 MHz segment of the downstream channel 110, which is the spectral bandwidth allocated to the cable television channel for the broadcast of program signals to all subscribers. (The international spectrum bandwidth is 8 MHz.) At the subscriber's location, the program signal is received by the set top box 138, while the downstream data is received separately by the cable modem 105 or 106. The number of upstream and downstream data channels in a given cable modem system is designed based on the service area, the number of users, the data rate assigned to each user and the available spectrum.

When the cable modem 105 or 106 is powered up, the Internet protocol (IP: Internet) can be transmitted downstream of the IP formatted data from the external network 114 to the cable modem 105 or 106. protocol is used to create a connection to the headend device 101. After powering on, the cable modems 105 and 106 receive channel assignments from the headend device 101. Cable modems 105 and 106 also contact a dynamic host configuration protocol (DHCP) server to download the name of the modem configuration file. Using this configuration file name, cable modems 105 and 106 contact a suitable trivial file transfer protocol (TFTP) server where the configuration file is stored. Finally, the configuration file is downloaded from the TFTP server to the cable modems 105 and 106. The information in the configuration file allows the cable modems 105 and 106 to identify which cable modem operating software is applicable and where the operating software can be downloaded to the cable modems 105 and 106.

The network manager executes network management functions to monitor and control various network elements. Exemplary network elements include cable modems 105 and 106, hosts, gateways, terminals, and servers. Each network element includes a management agent for executing network management functions as requested by the network manager. SNMP (Simple Network Management Protocol) protocol is used to convey network management information between the network management station and agents in each network element. The SNMP protocol defines a range of management information, a format for representing the management information, operations following management control, and the format and interpretation of data exchanges between management entities such as network management stations and management agents. Cable modems 105 and 106 may be configured to block access by unauthorized management stations.

According to the SNMP protocol, network management information is expressed in ASN.1 language (Abstract Syntax Notation, Version 1). The SNMP protocol defines various network management operations as changes or checks of variables in a TLV (type-length-value) data string stored within each network device agent. Thus, the network agent of the hardware device using the SNMP protocol interacts with the management station to retrieve (get) or change (set) the variables in the data string. The use of the TLV format limits the number of management functions that can be implemented by the management station to two: one operation assigns a value to a particular configuration or parameter data string and the other retrieves the value. Configurations or parameters that can be managed by the network manager are described in a management information base (MIB) in each network device agent.

The simple network management protocol is the most common protocol used by network management software applications to query or control a network agent. A network agent is software running on network devices such as workstations or routers, which in turn has the ability to gather information about device operations that can be retrieved by the network management station. The network management station collects and stores this data. Both network managers and network agents run network management software to enable data exchange between network managers and controlled network agents. In addition, the network management station executes network management software to enable network management functions, as is well known to those skilled in the art. The Internet Protocol version of SNMP is used by most network management software applications. The SNMP protocol runs on top of the Internet protocol.

The Management Information Base (MIB) describes data that can be retrieved or changed over the network by the network management station. Through the management information base, the network management station knows what information the network agent has and which aspects of the device are controllable. Control functions executed by the network manager include those relating to the operation of the device itself and device interaction with the network.

The management information base on the network agent is a repository of characters that identify certain operating parameters of the network device, such as a network interface card, hub, switch, or router. By changing these parameters, the network manager controls the network device. In addition to controlling the network device associated with it, the network agent collects statistics and responds to questions from the network manager in a manner specified by the applicable protocol.

As mentioned above, DOCSIS certified cable modems are configured by downloading configuration files from a TFTP server. The configuration file may include parameters formatted as SNMP type-length value words. The type field of the type length value format is a single byte identifier that specifies the configuration parameter described in the value field. The length field is also a single byte field that identifies the length of the next value field. The value field can range from 1 to 254 bytes and contains certain values of the configuration parameter. Cable modems 105 and 106 must handle all SNMP TLV's in the file, but ignore inappropriately formatted or unknown TLV's. Once an error is detected in the file type, the TLV's of that type are no longer processed. Thus, there is a need for a more efficient TLV's processing that allows for the processing of valid TLV's while allowing faulty or unknown TLV's to be ignored.

Each of cable modems 105 and 106 includes a network management agent and its associated MIB's. The DOCSIS specification identifies those MIB's that must be supported by the cable management network management agent. Each MIB refers to one or more attributes or features of the device, each attribute or feature indicated by an object identifier, also referred to as an OID. Each OID is a multiple digit number with digits separated by periods. For example, 1.3.5.7.8.10.12.3 is an OID. OID's for configurable or configurable device attributes are also associated with values for attributes such as speed, time, temperature. Non-configurable device attributes simply provide information, so the OID is not associated with a configurable element.

One technique for configuring cable modems is to place the OID in a configuration file and require the cable modem to handle the OID's as if they were set up by the network management station. As an example, there are certain OID's that determine which network managers are allowed access to the cable modem. Those who are familiar with the detailed operation of the cable modem can power cycle the modem, thereby enabling several features (by setting up some object through object identifiers), and by means of other network managers Other objects can be further configured to block access to the modem. If access is blocked, the objects cannot be reset or read by the network management station associated with the cable system. To prevent such occurrences, when the cable modem is powered on, appropriate information is included in the configuration file that sets the security features. Once the security features are set, only network management stations as identified in the security settings can be accessed and can set or record cable modem objects. In this way, the cable system operator ensures that only authorized network management stations can access the cable modem network agent.

The present invention relates generally to cable modems and, more particularly, to a method and apparatus for robust processing of cable modem configuration files in which the file is formatted as simple network management protocol (SNMP) objects.

1 and 2 are electrical block diagrams of a typical prior art bidirectional cable communication system.

3 illustrates a data packet unit in accordance with the teachings of the present invention.

4 is a process flow diagram embodying the teachings of the present invention.

The invention may be more readily understood when considered in view of the description of the preferred embodiments and the following figures, and further advantages and uses become more readily apparent.

Before describing in detail the particular method and apparatus for processing simplified management protocol type length value words in accordance with the present invention, it should be observed that the present invention primarily exists as a new combination of steps and device elements. Accordingly, the hardware components and method steps are those relevant to the present invention so that the disclosure will not be obscured by structural details having the benefit of the description herein, which will be readily apparent to those skilled in the art. In the drawings, only specific details are represented by conventional elements.

Under the SNMP standard, each object identifier is a numeric value representing some aspect or feature of a management device, such as cable modems 105 and 106. Object identifiers (or OID's) can be used to identify a particular object or column in a table, each consisting of a series of numbers. The MIB defines a series of numbers so that both network agents and network management stations can interpret them.

Upon reception of the configuration file at modem startup, the modems 105 and 106 receive a plurality of TLV's for processing. Cable modems 105 and 106 separate the TLV words into a plurality of packet data units based on the type field. OID's represent one type of TLV words, so all OID's are grouped into one packet data unit for processing. OID numeric strings are values in TLV format. Prior art SNMP agents according to applicable standards process all OID's as a single group until an error is detected for TLV's processing. Once an error is detected, the OID's of the packet data unit are no longer processed. An error and a failure to handle the remaining OID's can generate configuration errors or limit the network manager's ability to control and monitor the network agent.

In accordance with the teachings of the present invention, in cable modems 105 and 106, OID's are first sorted by lexicographical ordering by the network agent. It is based on the number of digits of the OID. For example, all six digit OID's are grouped together: all seven digit OID's are grouped together, and so forth. In addition to or instead of the lexicographical order, OID's are sorted by scalar (ie, single object values) and tabular object values. A table object value is one in which multiple objects are contained within a single row. Rather than treating all OID's as a group, the present invention groups OID's into multiple packet data units. In one embodiment, all scalar values are processed after being packaged in a single packet data unit. In addition, all table objects are packaged into single packet data for processing, or all OID's for a single table row are grouped into packet data units. In another embodiment, all identical digit OID's are packaged into a single packet data unit.

The following examples clarify the teachings of the present invention. Like the two described below, scalar values that always end with "0" are grouped together.

1.3.6.1.2.1.1.4.0 sysContact

1.3.6.1.2.1.1.5.0sysName

OID digits 1.3.6.1.2.1.1 identify the system group for the network agent. Two objects were identified above, one identified by the ".4" digit, and the other object by the ".5" digit. Two object identifiers terminate with zero and contain scalar values. In accordance with the rules for these objects, both provide read / write access by the network management station. The "sysContact" object is a textual identification of the contact for this managed node along with information about how to contact that person. The "sysName" object is the administratively assigned name for the managed node. Typically this is the full authorized domain name of the node.

These three objects are the table values taken from the same table and are therefore grouped together. Final (7) indicates that these objects are from the seventh row in the table. The second digits 2, 3 and 4 from the ending identify the second, third and fourth columns of the seventh row. Mark OID's never end with zero; Instead, they end with rows. According to the invention, it is further noted that these objects are separated from the two objects described above due to the different number of digits in the OID.

1.3.6.1.2.1.1.9.1.2.7sysORID

1.3.6.1.2.1.1.9.1.3.7sysORDESCR

1.3.6.1.2.1.1.9.1.4.7sysORUptimeNODE

The next three objects are also grouped together and identify columns 2, 3 and 4 because they are located in the fifteenth row of the table.

1.3.6.1.2.1.2.2.1.2.15ifDEFCR

1.3.6.1.2.1.2.2.1.3.15ifTYPE

1.3.6.1.2.1.2.2.1.4.15 ifMTU

As described above, objects defined with the same MIB share all the same OID digits up to the point where unique OID's need to identify different objects as defined by the MIB.

4 illustrates a process for processing objects in accordance with the teachings of the present invention. 4 begins at start step 210 and proceeds to step 212 where a configuration file is received by cable modem 105 or 106. Although a configuration file may be used as an example to which the teachings of the present invention may be applied, those skilled in the art recognize that the teachings may be applied to any network management using TLV and SNMP parameters in the form of OIDs. In step 214, SNMP objects in the configuration file are identified. Recall that the configuration file contains multiple parameters for setting up and configuring the cable modem; Many of these parameters are not related to network management aspects associated with the SNMP protocol. At decision step 215, a determination is made whether any OID's to be processed remain. If not present, the process moves to an operational state 226.

If the OID's to be processed remain, processing proceeds to step 216 where the OID's are evaluated. In essence, OID's have the same number of digits and only one digit value is separated from the other OID's in the group. To implement this grouping arrangement, at step 216, the number of digits in the OID is counted. The process then moves to decision step 218 to compare the number of digits of the oldest OID with the number of digits of the currently processed OID. For the first pass through decision step 218, the result is positive because there is no previous value for comparison. In affirmative response at decision step 218, processing moves to decision step 220 to compare the individual digit values of each OID. Recall that all OID's for a given object differ in only one digit. For the first pass through decision step 220, if the response is affirmative, processing returns to step 216 to retrieve and evaluate the next OID. Now, processing moves to decision step 218 to evaluate the next OID. If the first and second OID's have the same number of digits, the result at decision step 218 is positive and the process moves to decision step 220. Here, if the individual digits of OID's are examined and they differ only in one digit value, the process returns to step 216. In this way, as steps 216, 218, and 220 are executed, a similar group (with the same number of digits and only one digit value is defined as different) is formed. This group is closed when either of the decision steps 218 or 220 generates a negative response (see step 222). Once a group of similar OID's called packet data units is formed, they are processed in step 224. As discussed above, a group is called a packet data unit. The processing of the OID's involves determining if there are any errors or faulty bits, and setting the object so that the OIDs refer to the value associated with the OID. Further, in accordance with the teachings of the present invention, all scalar OID's are separated from table OID's, and table OID's from the same table are grouped together in one packet data unit.

Thus, in accordance with the teachings of the present invention, individual faulty or unreadable objects in the packet data unit do not cause all OID's in the configuration file to be ignored. Instead, since each packet data unit contains only the associated OID's, if a single OID in the packet is faulty and thus the entire packet is discarded, then the OID's in other packets are not affected, and thus device features or aspects. To establish or set them. This technique ensures maximum utilization of various SNMP objects, and thus provides maximum network management capabilities through network / manager agent relationships. In the prior art, multiple objects of a packet data unit are ignored when only one object is faulty or unreadable, thus limiting network management functionality.

Although the present invention has been described with reference to the preferred embodiments, those skilled in the art will understand that various changes may be made and equivalent elements may be substituted for them without departing from the scope of the present invention. In addition, modifications may be made to adapt to a particular situation that is more important to the teachings of the present invention without departing from its essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (19)

A method of processing a plurality of object identifiers in a network having a network manager for controlling the plurality of network agents through the use of object identifiers, the method comprising: Classifying the object identifiers into groups of similar object identifiers, Gathering each group of similar object identifiers into a packet data unit, and Processing each packet data unit independently. The method of claim 1, And the similar object identifiers include all object identifiers including n digits. The method of claim 2, The similar object identifiers include all object identifiers having n digits, and all values of the n digits are the same except for one value. The method of claim 1, And the similar object identifiers include all scalar object identifiers. The method of claim 1, And the similar object identifiers include all table object identifiers. The method of claim 4, wherein And the table object identifiers are grouped according to the number of table rows. The method of claim 1, And the network agents are associated with network devices. The method of claim 6, And the network devices comprise cable modems. In a cable system wherein network devices are configured via a configuration file comprising configuration variables in a format identifiable by a network agent, the method of processing a plurality of configuration variables, (a) identifying the configuration variable with n digits, (b) of each group of configuration variables having n digits, identifying the configuration variables different from only one digit in the n digits, (c) gathering the identified configuration variables into a packet data unit, and (d) processing each packet data unit. The method of claim 9, And the packet data unit includes all scalar configuration variables that have the same number of digits and differ only in the value of one of the digits. The method of claim 9, Wherein each packet data unit comprises table configuration variables in the same table row. The method of claim 9, And the configuration variables comprise object identifiers. The method of claim 9, And the network devices comprise cable modems. A computer usable medium having computer readable program code for processing a plurality of object identifiers in a network having a network manager for controlling the plurality of network agents through the use of object identifiers, the method comprising: Computer readable program code configured to classify the object identifiers into groups of similar object identifiers, Computer readable program code configured to aggregate each group of similar object identifiers into a packet data unit, and An article of manufacture comprising the computer usable medium containing computer readable program code configured to process each packet data unit independently. The method of claim 14, Wherein the similar object identifiers have n digits and include all other object identifiers at only one value of the n digits. The method of claim 14, The similar object identifiers include all table object identifiers. The method of claim 14, Wherein the similar object identifiers include all table object identifiers from the same table row number. The method of claim 14, The network agents include cable modems. An apparatus for processing a plurality of object identifiers in a network having a network manager for controlling the plurality of object agents through the use of object identifiers, the apparatus comprising: A first module for classifying the object identifiers into groups of similar object identifiers, A second module that aggregates each group of similar object identifiers into a packet data unit, and And a third module for independently processing each packet data unit.