Bandwidth management is the process of measuring and controlling the communications (traffic, packets) on a network link, to avoid filling the link to capacity or overfilling the link, which would result in network congestion and poor performance of the network. Bandwidth management is measured in bits per second (bit/s) or bytes per second (B/s).
Bandwidth management mechanisms and techniques
Bandwidth management mechanisms may be used to further engineer performance and includes:
Traffic shaping (rate limiting):
Token bucket
Leaky bucket
TCP rate control - artificially adjusting TCP window size as well as controlling the rate of ACKs being returned to the sender
Scheduling algorithms:
Weighted fair queuing (WFQ)
Class based weighted fair queuing
Weighted round robin (WRR)
Deficit weighted round robin (DWRR)
Hierarchical Fair Service Curve (HFSC)
Congestion avoidance:
RED, WRED - Lessens the possibility of port queue buffer tail-drops and this lowers the likelihood of TCP global synchronization
Policing (marking/dropping the packet in excess of the committed traffic rate and burst size)
Explicit congestion notification
Buffer tuning
Bandwidth reservation protocols / algorithms
Resource reservation protocol (RSVP)
Constraint-based Routing Label Distribution Protocol (CR-LDP)
Top-nodes algorithm
Traffic classification - categorising traffic according to some policy in order that the above techniques can be applied to each class of traffic differently
Issues which may limit the performance of a given link include:
TCP determines the capacity of a connection by flooding it until packets start being dropped (Slow-start)
Queueing in routers results in higher latency and jitter as the network approaches (and occasionally exceeds) capacity
TCP global synchronization when the network reaches capacity results in waste of bandwidth
Burstiness of web traffic requires spare bandwidth to rapidly accommodate the bursty traffic
Lack of widespread support for explicit congestion notification and Quality of Service management on the Internet
Internet Service Providers typically retain control over queue management and quality of service at their end of the link
Window Shaping allows higher end products to reduce traffic flows, which reduce queue depth and allow more users to share more bandwidth fairly
Packet sniffer
Network traffic measurement