Side_1_360

4 End-to-end QoS Support

in UMTS

In Chapter 3 we described the QoS functionality
internally to the UMTS network and the differ-
ent components necessary to support QoS for
different traffic types. To be able to support end-
to-end QoS there has to be mechanisms to trans-
late the UMTS QoS parameters to external QoS
mechanisms and protect the UMTS network
from external networks, e.g. given by policy
rules. These rules contain information regarding
what traffic is allowed to enter the other opera-
tors’ domains, how to ensure that the rules are
not violated and what action to take if the rules
are violated. As Figure 3-2 depicts, the UMTS
bearer service interfaces the external bearer ser-
vice at the GW node, i.e. the GGSN. The GGSN
therefore acts as the EDGE node towards exter-
nal networks. The GGSN has therefore been
equipped with functionality to police traffic
entering and leaving the UMTS network and
(re)negotiate external resources by communicat-
ing with external resource managers, e.g. by
means of RSVP signalling.

In the following we describe the main function-
ality for end-to-end QoS provisioning in UMTS.
In particular, we describe the concept of the IP
bearer manager and the IP policy framework
applied to UMTS. Finally we address the prob-
lem of co-ordination of the call control with the
bearer control.

4.1 IP Bearer Manager

Figure 4-1 depicts the enhanced QoS framework
indicating the new entities necessary for end-to-
end IP layer QoS support. Both at the UE and at
the GGSN a new functional entity known as the
IP bearer manager is depicted. Not all UEs are

expected to have implemented an IP bearer man-

ager. For these terminals end-to-end QoS is pro-

visioned by UMTS internal QoS mechanisms

within the UMTS network (i.e. PDP context)

and these are mapped to external QoS mecha-

nisms at the GGSN. The IP BS Manager in the

GGSN is used to control the external IP bearer

service and communicate with the eventual UE’s

IP Bearer manager entity for end-to-end QoS

(re)negotiation. As described earlier the UMTS

bearer manager controls the QoS internally in

the UMTS network. To support end-to-end QoS

the UMTS bearer service manager has to com-

municate with the IP bearer service manager,

and vice versa.

Due to the usage of different QoS mechanisms

within the IP network, the IP bearer manager

communicates with the UMTS BS manager

through a translation function (ref Figure 4-1).

The translation function translates the external

QoS classification to UMTS specific QoS classi-

fication and vice versa. For example the UMTS

QoS classes have to be translated into external

QoS mechanisms, e.g. DiffServ code points.

This translation is similar to the mapping func-

tion from UMTS QoS classes to/from the Diff-

Serv implementation across the Iu and Gn inter-

face as described in 3.5.2.

4.2 IP Layer UMTS Policy Framework

The policy framework in UMTS is constructed

very similar to the IETF policy framework as

described in IETF RFC 2753 “A Framework for

Policy-Based Admission Control”. The two main

RAB

Manager

UTRAN CN EDGE Gateway Ex.

Netw.

protocol interface

UE

UTRA

ph. BS M

UTRA

ph. BS M

lu NS

Manager

lu NS

Manager

BB NS

Manager

BB NS

Manager

Radio BS

Manager

Radio BS

Manager

lu BS

Manager

lu BS

Manager

CN BS

Manager

CN BS

Manager

UMTS BS

Manager

UMTS BS

Manager

UMTS BS

Manager

Transl. Transl.

IP BS

Manager

IP BS

Manager

Ext.

Service

Adm/Cap Control

Control

Adm/Cap

Control

Adm/Cap

Control

Subsc.

Control

Adm/Cap

Control

local

SIP proxy

Policy Control

Function

P-CSCF

service primitive interface

Figure 4-1 QoS management

functions for the end to end

IP QoS