Network Bandwidth Throttling: Overview

Network Bandwidth Throttling lets you limit the amount of bandwidth that network-based operations, such as between clients and MediaAgents, are allowed to consume. This is useful for minimizing network traffic congestion.

Throttling is configurable at two levels:

  • Traffic between two network endpoints (clients and/or MediaAgents) can be throttled for all operations between those two endpoints. Optionally, you can define a schedule for when this applies. This throttling is set for client groups or clients (which includes MediaAgents).
  • You can also throttle traffic for only backup operations (at the subclient level) and auxiliary copy operations (between two MediaAgent computers).

Network traffic can be throttled when sending or receiving, or both.

Important: By default, network throttling is not enabled. You can enable it and set rules for individual clients, client groups, and MediaAgents. Once configured, the throttling options are applied to all data transfer and control message operations, such as backup (including laptop backups), copy (including DASH copy), and restore.

Multiple rules can be created for a client or client group. If multiple rules are defined, and their schedules and clients overlap, the lowest applicable value is used.

Available Limiting Methods

Bandwidth can be limited either at an absolute level (a hard limit set in Kilobits per second), or as a percentage of available bandwidth (known as relative bandwidth throttling). Relative bandwidth throttling is useful for ensuring acceptable performance when bandwidth available to the client computer is limited.

How Relative Bandwidth Throttling Works

While sending or receiving, each client in the group monitors the rate at which it can send and/or receive data. As long as the threshold you enter is below the unthrottled actual rate, clients send or receive as fast as the network will allow. If the actual transmission rate for a client in the group falls below the threshold you set, the client begins sending or receiving data at only the throttling percentage you have set. For example, if your threshold is 500Kb/sec, and your percentage is 40%, transmission is throttled back to 200Kb/sec.

The client imposes this constraint for a fixed period, then attempts to operate at full speed again. If it finds that conditions have improved (that is, that it can now send or receive data at a rate greater than the threshold you set), it begins sending data at whatever speed the network supports. If it still cannot send send or receive data above the threshold rate, it continues to operate at the throttled percentage for another period, then checks again, and so on, until the job completes.