South-bound vs North-bound Interfaces used for Network Management

Most people involved in the Network Management get confused with two terms frequently used to describe the interconnections between the network and the network managers as well as the interconnections between various management systems (OSS).

The terms that get people confused are:

• South Bound Interfaces (SBI)
• North Bound Interfaces (NBI)

The analogy used to name these interfaces is that of a compass, and can be explained with the below figure:

About South Bound Interfaces (SBI)

The South Bound Interfaces (SBIs) allow Network Management Systems to connect to the Network Elements (NEs) and manage them. Although SNMP is the most common one, actually there are a lot of other options available and sometimes these are used together with SNMP in order to perform actions that are not available for whatever reason from SNMP.

In particular, integration of Network Elements (NE) to Network Management Systems (NMS) is provided by the following interfaces:

• SNMP
• CLI
• FTP / SFTP
• Telnet / SSH

Read below an overview of the above interfaces, that can be used as a quick reference when comparing and analyzing Network Management Systems.

SNMP overview

SNMP is a TCP/IP-based network management protocol working at the application layer and using the UDP protocol at the transmission layer.
The SNMP interface typically supports the SNMPv1 /v2c standard and sometimes the v3 standard, and is used to connect to (and manage) elements implementing SNMP agents.

CLI overview

The Command Line Interface (CLI) is an interactive user interface toward an Network Element. With CLI, users respond to a visual prompt by typing in a command on a specified line, receive a response back from the system, and then enter another command, and so forth.

FTP/SFTP overview

FTP and SFTP are typically used for backing up Network Element data and upgrading NE software. FTP / SFTP are TCP/IP-based network management protocols working at the application layer and are dependent on the UDP protocol.
File Transfer Protocol (FTP) is a set of standard protocols for transferring files on networks. FTP transfers passwords and file contents in plain text. SSH FTP (SFTP) uses the SSH protocol to provide secure file transfer and processing. With SFTP, passwords and data are encrypted during transmission.

Telnet and SSH overview

Telnet and SSH are basic types of interfaces used for the remote login and management of the NEs. Telnet / SSH sometimes allow Network Managers to perform specific management functions not available through SNMP.

Telnet is a TCP/IP-based network management protocol working at the application layer. Users can login in to an NE and use CLI to run commands usually related with NE configuration and maintenance. Using the TCP protocol at the transmission layer, the Telnet protocol provides services for network communication. The Telnet protocol transmits communication data in plain text, which is not secure.

Secure Shell (SSH) is also a TCP/IP-based network management protocol working at the application layer. SSH makes use of the TCP protocol at the transmission layer for transmitting data encrypted at the application layer.

About North Bound Interfaces (NBI)

The North Bound Interfaces (NBIs) can comply with ITU-T or TMF series of standards and are used to enable  Alarm / Performance / Inventory / Provisioning / Configuration / Security related info of Network Elements to be forwarded to higher level management system than the NMS, typically referred to as OSS systems.

In particular, northbound integration is provided through the following interfaces:

· XML
· FTP
· SNMP
· SYSLOG · TACACS · LDAP

· CORBA is also another option, available from legacy management systems.

North Bound Interfaces typical usage

Not all interfaces are suited for all management features. It is common to use a particular interface for a specific function, e.g. to use SNMP to forward alarms to North Bound OSS systems. The below table presents this in detail: