SKBPRIO(8)              (13 August 2018)               SKBPRIO(8)

     NAME
          skbprio - SKB Priority Queue

     SYNOPSIS
          tc qdisc ... add skbprio [ limit packets ]

     DESCRIPTION
          SKB Priority Queue is a queueing discipline intended to pri-
          oritize 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 straight-
          forward 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.

     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

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     SKBPRIO(8)              (13 August 2018)               SKBPRIO(8)

          priority packets when there is enough bandwidth.

     PARAMETERS
          limit
               Maximum queue size specified in packets. It defaults to
               64.  The range for this parameter is [0, UINT32_MAX].

     SEE ALSO
          tc-prio(8), tc-skbedit(8)

     AUTHORS
          Nishanth Devarajan <devarajn@uci.edu>, Michel Machado
          <michel@digirati.com.br>

          This manpage maintained by Bert Hubert <ahu@ds9a.nl>

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