Exploration of Data Center Automated Operation and Maintenance Technology: NETCONF

Data center switches realize automated operation and maintenance (O&M). Zero configuration online technology (ZAM) only completes the fixed configuration known in advance, mainly some basic intercommunication and login-related configuration. Future services are changing, so specific service-related configurations need to be configured or updated according to particular needs. NETCONF (Network Configuration Protocols) protocol provides a solution for automated service configuration deployment.

So how did NETCONF come about? Why did NETCONF need to be developed? What can NETCONF do? What is its development trend? This article will introduce and discuss data center operation and maintenance automation technologies in response to the above questions.
 

Problems with SNMP

When talking about NETCONF, SNMP cannot be avoided. SNMP (Simple Network Management Protocol) was first developed by IETF (Internet Engineering Task Force) in the late 1980s. Since its birth, SNMP has been used to monitor (such as alarms and performance management) network devices. Most professional network devices have SNMP agents. These agents are activated and configured to communicate with SNMP management NMS (Network Management System).

A complete SNMP system includes the management information base (MIB), structure of management information (SMI), and SNMP message protocol.

1. MIB

MIB, a Management Information Base, summarizes and stores the unique correspondence between resources and OIDs. NMS finds the corresponding OID in MIB according to the queried resources and sends the read OID information to the network device through an SNMP query message. The network device queries the corresponding resource information according to OID, and finally encapsulates it into an SNMP response message and sends it to NMS.

As shown in Figure 1, the OID corresponding to the query resource iso.org.dod.internet.mgmt.mib.ip.ipInReceives is 1.3.6.1.2.1.4.3.

Figure 1: MIB tree hierarchy

2. SMI

SMI (Structure of Management Information), is a language used in SNMP to define specific data in managed network entities (i.e., network devices). It defines data types, object models, and rules for writing and modifying management information.

3. SNMP Message

SNMP specifies five types of protocol data units (PDUs) (SNMP messages) for information exchange between management processes and agents.

As shown in Figure 2:

●  get-request, used to retrieve one or more parameter values from the proxy process;

● get-next-request, used to retrieve the next parameter value following the current parameter value from the proxy process;

● set-request, used to set one or more parameter values of the proxy process;

● get-response, used for one or more parameter values returned by the agent to the management process;

● Trap: A message actively sent by the agent process to notify the management process that certain events have occurred.
 

Figure 2: Five types of SNMP message operations
 

From the design of the SNMP protocol, we can see that although it has some configuration functions, SNMP itself is not a configuration-oriented protocol, nor is it suitable for developing client applications for configuration. A large number of operation and maintenance practices have also proved that SNMP is more of a tool for monitoring the status of network devices, and at the configuration management level, SNMP cannot yet become a mature tool.

Even at the network device monitoring level, SNMP still has other problems, such as:

●  Poor performance and low efficiency;

● Based on UDP protocol transmission, the reliability is poor and can only rely on its mechanism to ensure reliability, which affects performance;

● Private MIB makes it difficult to uniformly manage devices from multiple manufacturers.

It is precisely because of the various deficiencies and defects of SNMP that NETCONF was created.

The origin of NETCONF

In 2001 and 2002, the IAB ( Internet Architecture Board) organized several special working meetings on network management, bringing together network managers and protocol developers to discuss the problems of the mainstream network management protocols ( SNMP, CLI, etc.) simultaneously. The meeting results eventually formed RFC 3535. In this document, 14 requirements were proposed to address the problems in network management at the time, the most critical of which are:

●  Ease of use;

● Clearly distinguish between configuration data, data describing operational status, and statistical data;

● Configuration management for services and networks, rather than individual devices;

● Import and export of configuration data are independent of original personnel operations;

● Text-based configuration;

● Standardized data models, etc.

In response to the requirements listed in RFC 3535, the NETCONF working group was established in 2003, and the design of NETCONF follows RFC 3535. In 2006, the NETCONF core RFC 4741 was released, and in 2011, the updated version of RFC 6241 was released (repealing RFC 4741).

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