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What is Adaptive Session Balancing?
Adaptive Session Balancing (ASB) is the ability of a network appliance to dynamically distribute session traffic over multiple endpoints. This real-time balancing optimizes network efficiency and bandwidth usage at any given moment, giving IT administrators increased control over network traffic. ASB can help with maximizing connection speeds over many different network types, including open internet, VPN, and intranet traffic.
Often part of a broader effort at the business level, ASB serves as a way of maximizing traffic prioritization to better serve users. As an example, a company with geographically separated branches might use adaptive session balancing on their VPN, to ensure video conferencing traffic can be dynamically prioritized over less essential functions, like email traffic or off-site archiving.
Adaptive Session Balancing is used in contrast to Static Session Balancing, in which all sessions are distributed over network transports using a round-robin policy, without regard to available bandwidth or resources. Adaptive Session Balancing therefore can achieve superior resource utilization and user experience.
How Adaptive Session Balancing Works
In Adaptive Session Balancing, all sessions are initially balanced statically over primary and secondary transports. However, metrics on bandwidth and latency usage are constantly gathered so that sessions with a significant lifetime can be routed to the best endpoint.
When selecting the transport, the firewall also takes asymmetric links into account, selecting the transport that offers the best upstream or downstream performance based on the selected balancing policy.
ASB Criteria and Metrics
- Dynamic Bandwidth Detection (DBD): also referred to as Adaptive Bandwidth Detection, is the practice of allocating shared network bandwidth on the fly between client connections. DBD controls both the inbound and outbound bandwidth rate, and can adjust network speeds accordingly. For example, if a user is downloading multiple files off a server, dynamic bandwidth can increase the available resources to that user, by adjusting the total inbound bandwidth, thereby increasing their download speed.
- Latency Detection: is used to determine server reachability by measuring signal delay between each client and its server interaction. This information is used to determine the best connection available to each client.
- Packet Drop Rate: the measurement of data lost in transit between a client and server. Also helps to inform the session balancer about which available endpoint will offer the best connection to a client.