Editing Traffic policing (communications) (section)

== Implementations ==
On Cisco equipment, both traffic policing and shaping are implemented through the [[token bucket]] algorithm.<ref>[http://www.cisco.com/en/US/docs/ios/12_2/qos/configuration/guide/qcfpolsh.html#wp1012025 What is a token bucket?] at Cisco</ref>

Traffic policing in ATM networks is known as [[UPC and NPC|Usage/Network Parameter Control]].<ref>Hiroshi Saito, Teletraffic Technologies in ATM Networks, Artech House, 1993. {{ISBN|0-89006-622-1}}.</ref> The network can also discard non-conformant traffic in the network (using [[Priority Control]]). The reference for both traffic policing and traffic shaping in ATM (given by the [[ATM Forum]] and the [[ITU-T]]) is the Generic Cell Rate Algorithm ([[GCRA]]), which is described as a version of the [[leaky bucket]] algorithm.<ref name="ATMF-GCRA" >ATM Forum, The User Network Interface (UNI), v. 3.1, Prentice Hall PTR, 1995, {{ISBN|0-13-393828-X}}.</ref><ref name="ITU-T-GCRA">ITU-T, ''Traffic control and congestion control in B ISDN'', Recommendation I.371, International Telecommunication Union, 2004, Annex A, page 87.</ref>

However, [[Token bucket#Comparison to leaky bucket|comparison of the leaky bucket and token bucket]] algorithms shows that they are simply mirror images of one another, one adding bucket content where the other takes it away and taking away bucket content where the other adds it. Hence, given equivalent parameters, implementations of both algorithms will see exactly the same traffic as conforming and non-conforming.

Traffic policing requires maintenance of numerical statistics and measures for each policed traffic flow, but it does not require implementation or management of significant volumes of packet buffer. Consequently, it is significantly less complex to implement than ''traffic shaping''.