Side_1_360

Traffic management includes nodal traffic con-
trol (e.g. traffic conditioning, queue manage-
ment, scheduling) and other functions that regu-
late traffic through the network or control access
to network resources. These activities can be
carried out continuously and in an iterative man-
ner. The activities are commonly divided into
proactive and reactive. In the former preventive
and perfective actions can be found, while cor-
rective actions would be part of the latter.

The TE actions would operate on various time
scales; coarse (days, years – like for capacity
management), intermediate (ms, days – like for
routing control), and, fine (ps, ms – like for
packet level processing).

The TE subsystems include capacity augmenta-
tion, routing control, traffic control and resource
control. Inputs to the TE system would include
network state variables, policy variables and
decision variables. A challenge is to introduce
automated capabilities that adapt fast and effi-
ciently to changes in the network state, while
stability is maintained. Performance evaluation
is then a critical part of this, to assess the effec-
tiveness of a TE method, to monitor a network
state and to verify compliance with performance
levels.

3 TE Settings and Activities

3.1 Settings

A number of settings for exercising TE activities
are identified in [ID_tepri]. To some extent these
can also be considered as steps, see Figure 4.
However, considering that TE activities are car-
ried out continuously the different steps may be
active at the same time, although possibly look-
ing at different instances of time for implement-
ing the solutions into the network.

The settings described are:

• Networkcontext; describing the situations
  where traffic engineering challenges are
  found. Such situations include network struc-
  ture, network policy, network characteristics,
  network constraints, network quality attri-
  butes, network optimisation criteria, etc.
  A network can be represented as a system, see
  Figure 5, consisting of: i) a set of intercon-
  nected resources; ii) a demand representing
  the offered load; and iii) a response consisting
  of network processes, protocols and mecha-
  nisms that carry the offered load through the
  network. All these elements may have specific
  characteristics, which for example may limit
  the flexibility. Several types of demand
  classes may be present, similar to traffic
  classes although also different customer types
  should be taken into account. This results in a
  request for differentiated services. The net-

work resource and the traffic handling-related

mechanisms also have their characteristics.

Some detail of how the network provides the

services will be given by the policies speci-

fied. In [ID_tepri] it is stated that requirements

on the service provision (traffic handling) can

either be statistical (e.g. by rates and burst

sizes) or deterministic (e.g. some effective bit

rate measure). Requirements on the QoS are

either of the integrity type (e.g. packet loss)

or of temporal nature (e.g. delay, delay varia-

tion).

• Problemcontext; defining the issues that TE
  addresses, like identification, abstraction, rep-
  resentation, formulation, requirement specifi-
  cation, solution space specification, etc. One
  class of problems is how to formulate the
  questions that traffic engineering should
  solve; how to describe requirements on the
  solution space, how to describe desirable fea-
  tures of good solutions, how to solve the prob-
  lems and how to characterise and measure the
  effectiveness of the solutions. Another prob-
  lem is how to measure and assess the network
  state parameters, including the network topol-
  ogy. A third class of problems is how to char-
  acterise and evaluate network states under a
  variety of scenarios. This can be addressed
  both on system level (macro states – “macro
  TE”) and resource level (micro state – “micro
  TE”). This asks for appropriate levels of
  abstractions being identified. A class of prob-

Figure 3 Basic resource types

related considered for Traffic

Engineering

Figure 4 Settings for

exercising TE activities

Link bandwidth/transfer capacity

Processing/computing capacity

Buffer space/storage capacity

Network context:

TE challenges

Problem context:

issues addressed

Implementation and

operational context:

implementing and

maintaining the solutions

Solution context:

how to solve the TE

problems

time