очередь приоритета SKB (SKB Priority Queue)
Имя (Name)
skbprio - SKB Priority Queue
Синопсис (Synopsis)
tc qdisc ... add skbprio [ limit packets ]
Описание (Description)
SKB Priority Queue is a queueing discipline intended to
prioritize the most important packets during a denial-of-service
( DoS ) attack. The priority of a packet is given by
skb->priority , where a higher value places the packet closer to
the exit of the queue. When the queue is full, the lowest
priority packet in the queue is dropped to make room for the
packet to be added if it has higher priority. If the packet to be
added has lower priority than all packets in the queue, it is
dropped.
Without SKB priority queue, queue length limits must be imposed
on individual sub-queues, and there is no straightforward way to
enforce a global queue length limit across all priorities.
SKBprio queue enforces a global queue length limit while not
restricting the lengths of individual sub-queues.
While SKB Priority Queue is agnostic to how skb->priority is
assigned. A typical use case is to copy the 6-bit DS field of
IPv4 and IPv6 packets using tc-skbedit(8). If skb->priority is
greater or equal to 64, the priority is assumed to be 63.
Priorities less than 64 are taken at face value.
SKB Priority Queue enables routers to locally decide which
packets to drop under a DoS attack. Priorities should be
assigned to packets such that the higher the priority, the more
expected behavior a source shows. So sources have an incentive
to play by the rules.
Алгоритм (Algorithm)
Skbprio maintains 64 lists (priorities go from 0 to 63). When a
packet is enqueued, it gets inserted at the tail of its priority
list. When a packet needs to be sent out to the network, it is
taken from the head of the highest priority list. When the queue
is full, the packet at the tail of the lowest priority list is
dropped to serve the ingress packet - if it is of higher
priority, otherwise the ingress packet is dropped. This algorithm
allocates as much bandwidth as possible to high priority packets,
while only servicing low priority packets when there is enough
bandwidth.
Параметры (Parameters)
limit Maximum queue size specified in packets. It defaults to
64. The range for this parameter is [0, UINT32_MAX].
Смотри также (See also)
tc-prio(8), tc-skbedit(8)
