To understand a little more about DOCSIS specifications, you should start by understanding the OSI model a little more. The Open System Interconnection model is a conceptual model that characterizes and standardizes the communication functions of a telecom or computing system without regard to its underlying internal structure and technology. Its goal is the interoperability of diverse communication systems with standard communication protocols. It defines the interconnection of open systems under the conceptual model defined by the ISO (International Organization for Standardization), in which standard protocols are defined for various communications systems to communicate with each other. This model uses seven main layers, on which all the specifications to consider for the interoperability of constituents are based.
The specification of DOCSIS services is oriented to the different layers of the OSI model, centered on layers 1 and 2 of the model, allowing it to support different components of voice, data and TV. This specification has evolved over the last decades significantly. In 1996, the specification version 1.0 of the standard was generated, with some speed evolutions up to 3.1 in the year 2013. From this moment, the organizations supporting the standard continued improving different features until they arrived at version 4.0, whose specification was carried out in 2019.
Previous generations of DOCSIS were commonly referred to as DOCSIS interfaces 1.0, 1.1, 2.0, 3.0 and 3.1. DOCSIS 4.0 is compatible with earlier versions of integrated equipment with earlier specifications, except for DOCSIS 1.0 CM. DOCSIS 4.0 compliant CM interoperates perfectly with DOCSIS 4.0, DOCSIS 3.1, and DOCSIS 3.0 CMTS. DOCSIS 4.0 compliant CMTS supports DOCSIS 3.1, DOCSIS 3.0, DOCSIS 2.0 and DOCSIS
The advantage of version 4.0 of the standard, compared to its previous versions, is based on the symmetrical transmission capacity (it is a type of connection in which the data upload and download speed is equal. For practical purposes, the speed at which a video is uploaded to youtube or played is the same). The fundamental pillars of this technology are:
- Speed: multigigabit symmetry for simultaneous loading and downloading of content
- Low latency: built into DOCSIS 3.1 and improved, which reduces the delay between the issuance and receipt of an operation/transaction.
- Improved safety: novelty in each new standard.
- Increased reliability: the ability to detect network problems.
For DOCSIS 4.0, functional areas of network management defined in the FCAPS model, which is the ISO application for data network management, are defined. Defines the features for the areas of Fault (Fault), Configuration (Configuration), Accounting (Accounting), Performance (Performance) and Security (Security). These definitions make it possible to define protocols to be considered for the different network elements so that the installed capacity can be supported. For each of the features you have:
- Fault management seeks to identify, isolate, correct, and record system failures.
- Configuration management modifies system configuration variables and collects configuration information.
- The accounts management collects statistics on the use of subscribers, statistics establishing usage fees, and invoices to users depending on their use of the system.
- Performance focuses on the collection of performance metrics, the analysis of these metrics, and the setting of thresholds and tariff limits.
- Security management covers the identification and authorization of users and equipment, provides audits and alert functions and provides a vulnerability assessment.
Basic Architecture DOCSIS 4.0
The general architecture proposed for DOCSIS 4.0 has the following basic components without including all of them.
- SNMP manager, which performs SNMP configuration and queries against the CM agent.
- Configuration file server, responsible for transferring configuration files to devices via TFTP or HTTP.
- Firmware file server responsible for providing firmware images to devices.
- Server for log or syslog storage.
- DHCP server is responsible for assigning IPv4 or IPv6 addresses, along with particular parameters that allow devices to obtain configuration files.
- Time server or ToD.
- IPDR collection servers for information collection between CM and CMTS.
- TR-069 server, which is under the protocol of the same name, allows the abstract of the maintenance of the devices that are in the end user. For this service, the final device must support the respective protocol.
- In the northern layer lies the entire business logic part, which is oriented to the management layer to meet the capabilities of contracted services.
In summary, the DOCSIS specification will make it possible to reuse the capacity installed in the network of operators, offering greater speed in their services based on capacity standards, monitoring and management and error resolution. It is time to assess the costs of making this change and identify the benefits of revitalizing the already installed network or switching directly to other technologies that offer higher speeds.