NAME

       skbprio - SKB Priority Queue

SYNOPSIS

       tc qdisc ... add skbprio [ limit packets ]

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.

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.

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>