Side_1_360

(between the terminal/host and the edge router)

while other schemes are used in other parts of

the network.

2.4.5 Functions Related to Network-

centric Admission Control

In order to implement an explicit full-guarantee

admission control, the features indicated in Fig-

ure 12 should be available. Note that some of

these may be optional depending on the configu-

ration and the overall solution for traffic han-

dling.

Pivotal for having admission control is naturally

to implement an algorithm making the admission

decisions (accept/reject). In order to carry out

such a ruling, the status of the resource situation

(and the present load) as well as characteristics

of the flow related to the request have to be

made available, i.e. given as input. As described

earlier this information could be provided by dif-

ferent means and with various levels of details

and dynamics. Additional inputs may also be rel-

evant, like user/application profiles that could be

part of policy matters. Another function needed

is called classification, i.e. that the packets arriv-

ing are recognised as belonging to the traffic

flow in question.

In addition to the mechanisms present in the net-

work, the terminal/application must also be able

to formulate, categorise and convey the relevant

information. An example of blocks adopted from

Windows/Microsoft is depicted in Figure 13.

The Subnet Bandwidth Manager (SBM) can be

considered as a server connected to the LAN

controlling the bandwidth usage between the

different hosts connected. The SBM is presented

in [RFC2814]. This can be considered as a sig-

nalling protocol supporting admission control

over IEEE 802-type networks by utilising RSVP.

Hence, it provides a method for mapping sig-

nalling protocols, like RSVP, onto the IEEE

802-type of networks, including operations of

terminals and routers in order to allow for reser-

vation of LAN resources.

From [Bern00a] admission control agents may

be allocated at key locations, referring to con-

gestion points. Examples of such are:

• Single interface: a classic RSVP model could
  be applied.


• DiffServ domain: admission control at ingress
  router may be introduced.


• 802-based domain: Subnet Bandwidth Manager
  (SBM) could be introduced, ref. [RFC2814].


• ATM subnetwork: admission control at ATM
  edge devices


• Provider domain: admission control as part of
  bandwidth broker.

Still in the end system, a congestion manager

may be implemented as described in [ID_cm].

Figure 13 Microsoft QoS
components, from [Bern00]

Traffic control

consumers

Traffic control

providers

Network management

application

QoS-aware

application

QoS SP

TCP/IP

Packet

scheduler

Netcards

Packet Classifier

TC API

WinSock2 API

SBM/ACS

ACS = Admission Control Service

SBM = Subnet Bandwidth Manager