Data monitoring switch
A Data Monitoring Switch is a networking hardware appliance that provides a pool of monitoring tools with access to traffic from a large number of network links. It provides a combination of functionality that may include aggregating monitoring traffic from multiple links, regenerating traffic to multiple tools, pre-filtering traffic to offload tools, and directing traffic according to one-to-one and many-to-many port mappings. Data Monitoring Switches enable organizations to use their monitoring tools more efficiently, to centralize traffic monitoring functions, and to share tools and traffic access between groups.
Several other terms have been used to describe this class of device, including data access switch, tool aggregator, net tool optimizer, and distributed filter tap.
Function
A Data Monitoring Switch typically provides 24 to 38 ports in a 1U 19-inch chassis, with higher port density devices expected in the future. Ports may be dedicated as network inputs or tool outputs, or may be configurable as either. Network input ports may be paired to provide in-line connectivity (integrated Tap function), or independent to take input from external network Taps or network switch SPAN ports. Some devices have the ability to interconnect chassis to configure logical systems with hundreds of ports.
When a number of monitoring tools are connected to the Data Monitoring Switch’s tool ports, copies of traffic from any of the network ports can be switched to any of the tools using the data monitoring switch’s management interface. A unique characteristic of the Data Monitoring Switch, as opposed to matrix switches and aggregating Taps, is that it can support a flexible set of port mappings including:
- One network link to one monitoring tool
- One network link to many monitoring tools (regeneration)
- Many network links to one monitoring tool (aggregation)
- Many network links to many monitoring tools
In addition to directing monitoring traffic, Data Monitoring Switches are capable of filtering traffic by Layer 2 to Layer 4 protocol criteria such as protocol and IP address, enabling only traffic of interest to be sent to specific tools. This capability can prevent tool oversubscription and facilitate drilling down on issues.
Additional capabilities found in some Data Monitoring Switches include load balancing across multiple tool ports, filtering on patterns in packet payloads, and converting media and data rates so tools can be used to monitor traffic from dissimilar links. [1]
Device Management
Most Data Monitoring Switches support several management interfaces:
- A text-based command-line interface (CLI) accessed with a terminal emulation program either locally over a serial port or remotely over a secure (e.g., SSH) network connection; this interface is usually preferred by network administrators
- A Web browser based graphical interface; this interface is usually preferred by casual users and non-experts
- A platform (Windows) based server; this interface is preferred for managing a large number of devices through a single interface
- Third-party SNMP management tools; this interface in preferred in environments with centralized SNMP management systems such as IBM Tivoli or HP OpenView [2]
Advantages
Data Monitoring Switches facilitate centralizing network traffic monitoring in the NOC.
By providing remote monitoring and control, they save the time and expense of traveling to remote locations to install monitoring tools.
They make it easier to share tools among groups.
With data rate conversion capabilities, they enable 1 Gigabit tools to support 10 Gigabit links, and 10 Gigabit tools to monitor traffic aggregated from multiple 1 Gigabit links. [3]
They prevent tool oversubscription by pre-filtering traffic.
They can Tap network links directly, instead of relying on switch SPAN ports for monitoring access.
Because of their high port densities compared to discreet Taps, they save rack space and power, and can have a lower price per port.
They are fully passive, unable to disrupt network traffic in any circumstances. (Integrated Taps, if present have fail-to-wire on power failure.) This is compared to SPAN ports, where network traffic can be disrupted if the switch is not properly configured while setting up the SPAN port. [4]
Disadvantages
Data Monitoring Switches take a simple concept, the passive network Tap, and make it an expensive, complex device that requires configuration and management.
They are non-standard – different vendors’ devices operate and are managed differently.
Entry-level pricing is expensive – if just a few links or tools need to be instrumented, price per port will be high.
References
See also