Side_1_360

The different modules are:

• The RSVP process taking care of processing
  of RSVP PATH and RESV messages.


• The Policy control module being responsible
  for enforcing policies. That is, the policy con-
  trol module answers questions like “is the user
  allowed to do this” (ref. [Jens01a]).


• The admission control module being responsi-
  ble for ensuring that there are enough re-
  sources for the admitted flows. If there is a
  shortage of resources the admission control
  module will deny reservation requests.


• The Packet Classifier and Scheduler support-
  ing appropriate handling of the traffic flows.
  The Packet Classifier looks at every data
  packet to determine whether the appropriate
  flow has a reservation and which service class
  the flow belongs to. The Packet Scheduler
  then makes the forwarding decision according
  to the class.


• The RSVP process would also interwork with
  the Routing process since the routing informa-
  tion is subject to dynamic changes.

RSVP identifies a communication session by the
combination of destination address, transport-
layer protocol type, and destination port number,
as given by the Multi-Field. It is important to
note that each RSVP operation only applies to
packets of a particular flow; therefore, every
RSVP message must include details of the flow
to which it applies.

The primary messages used by RSVP are the

PATH message, which originates from the traf-

fic sender; and the RESV message, which origi-

nates from the traffic receiver. The primary

functions of the PATH message are firstly to

install reverse routing state in each router along

the path, and secondly to provide receivers with

information about the characteristics of the

sender traffic and end-to-end path so that they

can make appropriate reservation requests. The

primary function of the RESV messages is to

carry reservation requests to the routers along

the distribution tree between receivers and

senders.

RSVP messages can be transported “raw” within

IP packets using protocol number 46, although

hosts without this raw input/output (I/O) capabil-

ity might first encapsulate the RSVP messages

within a UDP header.

7.1.1 TE-related Parameters

As described above, the sender initiates a PATH

message, which carries a number of fields. Two

of these fields are of special interest as seen from

a traffic engineering point of view; Sender_TSpec,

and AdSpec. The Sender_TSpec field carries

information about the traffic to be generated.

This information is given as a set of token

bucket parameters: token bucket rate [r], token

bucket size [b], peak data rate [p], minimum

policed unit [m] and maximum packet size [M].

For IntServ, these parameters are given for both

Guaranteed and Controlled Load service class,

ref. Chapter 5.

The AdSpec field includes flags telling whether

or not resources can be reserved along the com-

Policy

Control

Module

Admis-

sion

Control

Admis-

sion

Traffic Control

Control

Traffic

Control

Host Router

RSVP Messages

Policy

Control

Module

RSVP

Process

Appli-

cation

Packet

Scheduler

Packet

Class-

ifier

Packet

Scheduler

Packet

Class-

ifier

RSVP

Process

Routing

Process

Figure 25 RSVP

implementation overview