In queueing theory, Kendall's notation (or sometimes Kendall notation) is the standard system used to describe and classify the queueing model that a queueing system corresponds to. First suggested by D. G. Kendall in 1953 as a threefactor A/B/C notation system for characterising queues, it has since been extended to include up to six different factors.
The notation now appears in most standard reference work about queueing theory. e.g. ^{[1]}
Contents 
A queue is described in shorthand notation by A/B/C/K/N/D or the more concise A/B/C. In this concise version, it is assumed K = ∞, N = ∞ and D = FIFO.
A code describing the arrival process. The codes used are:
Symbol  Name  Description 

M  Markovian  Poisson process (or random) arrival process. 
M^{X}  batch Markov  Poisson process with a random variable X for the number of arrivals at one time. 
MAP  Markovian arrival process  Generalisation of the Poisson process. 
BMAP  Batch Markovian arrival process  Generalisation of the MAP with multiple arrivals 
MMPP  Markov modulated poisson process  Poisson process where arrivals are in "clusters". 
D  Degenerate distribution  A deterministic or fixed interarrival time. 
Ek  Erlang distribution  An Erlang distribution with k as the shape parameter. 
G  General distribution  Although G usually refers to independent arrivals, some authors prefer to use GI to be explicit. 
PH  Phasetype distribution  Some of the above distributions are special cases of the phasetype, often used in place of a general distribution. 
This gives the distribution of time of the service of a customer. Some common notations are:
Symbol  Name  Description 

M  Markovian  Exponential service time. 
D  Degenerate distribution  A deterministic or fixed service time. 
Ek  Erlang distribution  An Erlang distribution with k as the shape parameter. 
G  General distribution  Although G usually refers to independent arrivals, some authors prefer to use GI to be explicit. 
PH  Phasetype distribution  Some of the above distributions are special cases of the phasetype, often used in place of a general distribution. 
The number of service channels (or servers).
The capacity of the system, or the maximum number of customers allowed in the system including those in service. When the number is at this maximum, further arrivals are turned away. If this number is omitted, the capacity is assumed to be unlimited, or infinite.
The size of calling source. The size of the population from which the customers come. A small population will significantly affect the effective arrival rate, because, as more jobs queue up, there are fewer left available to arrive into the system. If this number is omitted, the population is assumed to be unlimited, or infinite.
The Service Discipline or Priority order that jobs in the queue, or waiting line, are served:
Symbol  Name  Description 

FIFO/FCFS  First In First Out/First Come First Served  The customers are served in the order they arrived in. 
LIFO/LCFS  Last in First Out/Last Come First Served  The customers are served in the reverse order to the order they arrived in. 
SIRO  Service In Random Order  The customers are served in a random order with no regard to arrival order. 
PNPN  Priority service  Priority service, including preemptive and nonpreemptive. (see Priority queue) 
PS  Processor Sharing 
