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