Internet DRAFT - draft-xue-fmc-ps
draft-xue-fmc-ps
Network Working Group L. Xue
Internet-Draft B. Sarikaya
Intended status: Informational Huawei
Expires: April 25, 2013 D. von Hugo
Telekom Innovation Laboratories
October 22, 2012
Problem Statement for Fixed Mobile Convergence
draft-xue-fmc-ps-03.txt
Abstract
The purpose of this document is to analyze the issues that have
arisen so far and to propose several use cases for the Fixed Mobile
Convergence. This document gives a brief overview of the assumed
Fixed Mobile Convergence architecture and related works and then
introduces several Intarea type of use cases based on the partnership
in Fixed Mobile Convergence architecture, such as group
identification, mobility consideration, such as mobility status
reporting in Wi-Fi network.
Status of this Memo
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This Internet-Draft will expire on April 25, 2013.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 6
3. Key Issues in Fixed Mobile Converged Interworking . . . . . . 7
4. Group Id in Fixed Broadband Network . . . . . . . . . . . . . 7
5. UE Mobility in Fixed Broadband Network . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9.1. Normative References . . . . . . . . . . . . . . . . . . . 12
9.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
Growing availability of intelligent mobile devices and mature
networks of operators providing both reliable carrier grade
connectivity and affordable high bandwidth access offer to the
customer a nice climate of mobile broadband. With widespread
availability and easy usability of mobile broadband, mobile broadband
applications become more ubiquitous. Subscribers demand for various
service applications, especially Internet applications, such as
mobile Internet video, mobile Internet real-time communication, etc.
The subscribers requirements lay the foundation of mobile broadband.
On the other hand, simultaneously, the subscribers' services promote
the evolution of mobile broadband, which will impact the network
architecture. The flourishing mobile applications demand more and
more bandwidth offered by the operators. Even with wireless networks
becoming mature, such as 3G and LTE, the average bandwidth offered is
not comparable to data rates offered by fixed networks. With data
services rapidly increasing, the traditional cellular network
operating at a shared medium and thus being limited in transmission
rate often becomes the bottle-neck of mobile broadband. In addition
radio network technology generally requires high capital investment
and operational expenditures. Cellular network operators are facing
the challenge of increasing traffic demand at decreasing revenue and
have to provide means of more cost efficient access technology in a
highly competitive environment. With parallel availability of
different access technologies such as cellular and local wireless
networks a selection of the most (e.g. resource) efficient technology
is advantageous for both user and operator. Mobile industry has
specified functionalities to offload the data traffic to the fixed
broadband (FBB) network, via WLAN or a Home (e)NodeB (HNB or eNodeB,
aka. Femtocell) [TR23.829], which could alleviate traffic pressure
on the mobile network. That is to say, today, operators are able to
employ mechanisms to manage the subscriber service over both the
mobile and the fixed broadband network. We can say, FMC is emerging
on the basis of subscribers and operators requirements.
Fixed Mobile Convergence is a technology trend which aims to provide
the subscribers access to services regardless of the access network
type they are connecting to and provide the operators with the
flexibility to ensure transparency of services to the end user. For
a mobile subscriber to access services over both mobile and fixed
broadband networks seamlessly, additionally, the subscriber's end-to-
end service level agreement (SLA) must be maintained. This is
achieved by interworking between the control planes of the fixed
broadband network and the mobile network.
In the FMC interworking scenario addressed here, the fixed broadband
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network must partner with the mobile network to perform
authorisation, authentication, and accounting (AAA) and acquire the
policies for the mobile subscriber. Please note, a single converged
control plane, used for both the fixed broadband and the mobile
network, may be used in a truely converged, i.e. integrated
convergence scenario. This document only focuses on the interworking
scenario in this version. The convergence scenario is for further
study.
Figure 1 shows the assumed reference architecture of Fixed Mobile
Convergence Interworking for a Mobile (3GPP) Network and a fixed non-
3GPP access network as proposed by 3GPP and BroadBand Forum (BBF) as
an example in document [TR203].
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+--------------------------------------+
| Mobile Network |
| ---- |
| +------+ / \|
| +---+ PCRF | |Operator|
| | +---+--+ | Service|
| | | \ /|
| | | --+- |
+------+ +------+ | +------+ +---+--+ | | |
| UE | | eNB +----+ SGW +---+ PGW +----|---------+----------+
+------+ +------+ | +------+ +--+---+--+ | +------+| |
| +--+---+ +-|-----+M AAA || --+-
| | ePDG +--+ | +---+--+| / \
+------------+------+----|---------|---+ |Internet
| | | | Service
+---------------|--------|---------|---+ \ /
| Fixed Network | +---+--+ +---+--+| --+-
| | +---+ BPCF | |F AAA || |
| +--+-+-+ +------+ +---+--+| |
+------+ | | BNG +--------------+ | |
| Femto+----------+ +--+-+-+ | |
+------+ | | | +---------------------------+
+------+ | | +--+---+ |
| UE | | +----+ AN | |
+------+ +------+ | +--+---+ |
|WiFiAP|------------------+ |
| CPE | | |
+------+ | |
+--------------------------------------+
Legend:
M AAA Authentication Authorization Accounting in Mobile Network
F AAA Authentication Authorization Accounting in Fixed Network
AN Access Node
BPCF Broadband Policy Control Function
BNG Broadband Network Gateway
ePDG evolved Packet Data Gateway
PCRF Policy Charging Rule Function
PGW Packet Data Network Gateway
SGW Serving Gateway
UE User Equipment
CPE Customer Premises Equipment
Figure 1: Reference Architecture of Fixed Mobile Convergence
The policy and charging control (PCC) system is an important element
in FMC architecture. PCC system of FMC consists of policy decision
point (PCRF in the mobile network and BPCF in the fixed broadband
network) and the policy enforcement point (PGW and BNG,
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respectively), shown in Figure 1. PCC should support for controlling
the QoS (e.g., QoS class and bit rates) authorized for service, and
IP flow based charging. In FMC interworking scenario, these services
can be divided into four types.
1. Service via macrocell wireless network
2. Service via WiFi/Femtocell access routed back to 3GPP Evolved
Packet Core (EPC), where the fixed broadband network is used as
the access network,
* The service from a mobile UE is connected to WiFi or to
Femtocell Access Point (FAP) at the residential gateway (RG),
routed back to 3GPP Evolved Packet Core (EPC).
3. Services via WiFi access only fixed broadband routed
* The service from a mobile UE is connected to WiFi without
traversing the mobile network.
* In this scenario, the UE service may be guaranteed based on
subscriber's policy from the mobile network.
4. LIPA/SIPTO traffic
* Support of Local IP access (LIPA) and of Selected IP traffic
offload (SIPTO) for the Home (e)NodeB Subsystem and for the
macro layer network include a more integrated FMC scenario and
thus are for further study.
As for the services stated above, only the second and the third type
are related to FMC, where both the fixed broadband and the mobile
network are involved. The FMC architecture shall be capable to set
operator policies to support simultaneous access to these service.
In the network today, deploying FMC is a worthy way for operators to
satisfy subscriber's requirement and ease pressure from bandwidth.
In the following sections, we first describe the motivation and then
discuss the key issues that are at this time limited to the Intarea
and to FMC interworking scenario.
2. Conventions and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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3. Key Issues in Fixed Mobile Converged Interworking
There is a need to highlight and discuss the issues when facilitating
FMC. We systematically analyze the issues that have been proposed so
far and briefly assess the possible protocol extensions which could
solve the problems. In the network architecture, we target and limit
the scope to the interworking architecture for FMC.
Regarding the traffic management and control requirements in FMC
interworking scenario, these are the issues from an IETF Internet
Area and fixed broadband network point of view.
1. Group Id in fixed broadband network,
2. UE mobility status reporting in fixed broadband network.
There are many standardization issues related to FMC and protocol
extension work needed. If these issues are fixed, the advantages
brought out will be:
1. Optimize traffic management (per-UE granularity in the fixed
broadband network)
2. Enhance device management (via IP address synchronization between
fixed broadband network and mobile network)
3. Quick Responsiveness based on UE status
These issues are elaborated in the sections that follow.
4. Group Id in Fixed Broadband Network
Consumers in a fixed mobile convergence scenario nowadays are not
being limited by a single device such as only smart phone in
connecting to fixed broadband network. Increasingly, portable media
players, PCs, tablet, and mobile phones all belonging to the same
subscriber are being used. It is reported that more than 90
percentage of video streaming customers own more than one device.
Therefore, the same set of devices owned by one subscriber will have
the same personalized requirement. For example, one subscriber may
order the highest priority video streaming service from the operator,
an instant bandwidth tune service, security control, etc.
It is expected for consumers to receive network services seamlessly
in a convenient and economic way, irrespective of access
technologies. For example, consumers prefer to connect to the
Internet service via WiFi, instead of cellular access technology when
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moving into a Wi-Fi hotspot, if their mobile device is equipped with
WiFi (IEEE 802.11-based) interface.
Users must be able to access to services irrespective of the access
network. Operators need to have suitable user management ability, to
reduce the CAPEX and OPEX. For example, operators could apply the
unified policy control, and accounting control to the multiple
devices owned by one subscriber, or devices with multiple interfaces,
etc. This brings the need to identify each subscriber as one group
and given a group identifier.
Consider Figure 2 where several hosts are connected to the same RG in
a fixed broadband network. These hosts belong to different
subscribers. One of the subscribers has only one device shown as UE
in the figure. The second subscriber has multiple devices, one Pad,
one smart phone and a personal computer (PC). Each subscriber is
assigned a group id by the operator. Group Identifier (GroupId)
needs to be communicated to fixed broadband network nodes such as the
edge router (BNG).
A subscriber signs in the services of an operator. This subscriber
has several devices, e.g., two phones and one pad. She/he wishes to
share the subscription with these three devices. The operator could
assign a group id to the costumer, and any of the devices belonging
to the customer can be authenticated with this Id. Then all the
other devices can access the service - either in parallel or
sequentially - with unified policy control without additional
authentication.
A subscriber owns one pad and one Phone. This subscriber may take
photos on his trip away from home. It would be desirable that the
other device(s) which are left at home to be immediately syncronized
with these pictures in order to share them with the family. The
operator could ensure the device discovery belonging to one
subscriber by keeping an unified subscriber database in the network
containing all group ids of the subscribers.
Group id based traffic management changes the granularity of traffic
management that is currently in effect in cellular networks which is
based on per-UE or per-contract level. In current FMC procedures,
the broadband network can be made known of per-phone level traffic
control by way of the IP-CAN session [TS23.203] which denotes the
association between a UE and an IP network. The operator now will be
in a position to provide unified service to all the devices that
belong to the same group id, possibly carrying over UE's downloaded
traffic quality of service requirements to all other devices.
If several devices access service via multiple access technologies,
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the access technologies could belong to different network operators.
For example, WiFi network could be deployed by a different operator.
In this scenario, the subscriber ID semantics must be consistent
among these two operators. This can be achieved by agreement between
different operators.
Another problem that arises is efficient packet inspection.
Operators expect the fixed broadband network could be configured in
such a way that the traffic subject to packet inspection is routed
via the Traffic Detection Function (TDF) [TS29.212] usually
collocated with the edge router. Traffic inspection and then traffic
redirection that follows can be facilitated with group id. The same
inspection and redirection (to the local home network, to the mobile
network or to the Internet) rules can be applied in a unified manner
to all devices belonging to the same group.
Group +----+
Id | UE | Internet
1 +----+ /
W ^ Mobile
Group +----+ i | Network
Id | PC | F +----+ |
2 +----+ i | AP | +----------+ +----------+
+----+ | & | | | | |
|Pad | L | RG |---| | +-------------+ | |
+----+ i +----+ | Access |---| Aggregation | | Edge |
+-----+ n | Node | | Network |---| Router |
|Phone| k | | +-------------+ | |
+-----+ +----------+ +----------+
RG
Figure 2: Group Identification in Broadband Network
As discussed before, there are many drivers for the identification of
GroupId when the same subscriber accesses the broadband network using
several devices. They include efficient packet inspection, QoS
enforcement, charging. We can note that all these functions in FMC
depend on being able to identify the subscriber to which the device
belongs, i.e. group identification.
The subscriber ID must be contained in the traffic packet of the
subscriber in order to achieve policy enforcement in the device node
in the network. Currently the group id is not being communicated in
an IP packet. There are several possibilities which provide
solutions. IP (v4 or v6) level solution would call for including
group identifier in every packet the user sends. Such an approach
facilitates packet inspection to provide required Quality of Service
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since by looking at each packet the subscriber can be identified.
ICMP (both v4 and v6) or TCP/UDP protocol extensions can also be
other solution approaches. In this case the group id sent at the
beginning needs to be paired with the IP address of the device.
Packet inspection can then be conducted by first detecting the
address and then identifying the subscriber followed by enforcement
specific to this subscriber. It is difficult to foresee which is the
suitable solution among the various possibilities, more work needs to
be done.
5. UE Mobility in Fixed Broadband Network
The users are the mobile subscribers in FMC. Note that all the
services depend on the substantive character of subscriber's
mobility. It is important for operators to capture the user device
when it is moving into or outside the network, even in WiFi access.
Besides, the application and service from the subscriber must be
guaranteed based on the policy of operators.
In mobile network today, there are many mature solutions offered for
user's mobility already. Herein, only mobility in fixed access,
i.e., WiFi access, will be considered. For example, the user device
is attached to the home LAN (e.g., WiFi ) network, and establishes a
connection back to the subscriber's mobile service provider network
via the fixed broadband network. The mobile operator should
cooperate with the broadband access operator to deliver proper policy
for the service from UE.
+----+ +------+ +----------+
| UE1| |AP&RG |----| |
+----+ +------+ | |
W | AN |\
+----+ i+------+ | | \
| UE2| F|AP&RG |----| | \
+----+ i+------+ +----------+ \ +----------+
\ | |
L +-------------+ | |
i | Aggregation | | Edge |
n | Network |-------| Router |
k +-------------+ | |
+----------+ / +----------+
+----+ +-----+ | | /
| UE3| |AP&RG|----| AN |/
+----+ +-----+ | |
+----------+
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Figure 3: UE Mobility in Broadband Network
The mobility considered in the fixed access does not consider the use
of a mobility protocol. Consider Figure 3 where there are many
mobile nodes, i.e. UEs connected to the fixed broadband network.
Status of these nodes at a given time needs to be communicated to the
network by the access points. In this section, we divide the
mobility status reporting capability into two cases:
1. UE is moving into or outside the coverage area of WiFi AP
2. UE's WiFi access is dormant or not.
Figure 3 shows an example of the scenario where mobile UEs are served
in WiFi deployment over the fixed broadband network. RG embeds WiFi
AP. Each UE is provided with an IPv4/IPv6 address assigned within
the local network. A point-to-point link is established between the
UE and the edge router.
BPCF in fixed broadband network must have partnership with PCRF in
mobile network in order to maintain the service level agreement
(SLA). In order to allow the PCRF to retrieve the UE's policy to be
passed onto the BPCF in the fixed broadband network, it is mainly
concerned about the traffic and UE identification binding used to
achieve the actual traffic control. The BPCF/BNG will perform the
policy control based on the binding.
Since plenty of UEs may move into the coverage of WiFi AP, it is
possible that large amount of resources will be needed at the BPCF/
BNG. For optimum operation, the resources need to be released when
the UE goes out of the coverage of WiFi AP. So timely detection of
UE detachments is crucial in fixed mobile convergence environments.
That is to say the configuration must be updated regularly to satisfy
that the WiFi AP can serve thousands of UEs and proper resource
allocation at the BPCF/BNG.
Possible solutions approaches include extending the Control And
Provisioning of Wireless Access Points (CAPWAP) architecture RFC 5415
[RFC5415]. Access Controllers using an extended protocol can be
charged to keep track of the mobility status of the UEs that are
connected to the fixed broadband network using IEEE 802.11 links.
However, in Fixed Mobile Convergence, this information is needed by
entities not necessarily co-located with the Access Controller.
In some cases, e.g. home networks, CAPWAP protocol is not commonly
used. In such cases, it becomes even more challenging to keep track
of the UE mobility status. Protocol solutions need to be developed
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to solve this problem. During the solution process, CAPWAP protocol
could be used as an example.
6. IANA Considerations
This document makes no request to IANA.
7. Security Considerations
Serious concern of mobile operators towards FMC approaches has been
the customer access via networks not under control of the operator.
Operators would like to keep their own high security measures to
prevent various kinds of fraud or attack to the operators services
and network entities. Well known risks and vulnerabilities involved
in using IEEE 802.11 with the CAPWAP protocol are documented in
[RFC5416]. Any additional security considerations arising from FMC
are TBD.
8. Acknowledgements
Many people provided comments that have been incorporated into this
document including Mohamed Boucadair, David Binet, Pierrick Seite,
Daniel Park and Cameron Byrne.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5415] Calhoun, P., Montemurro, M., and D. Stanley, "Control And
Provisioning of Wireless Access Points (CAPWAP) Protocol
Specification", RFC 5415, March 2009.
[RFC5416] Calhoun, P., Montemurro, M., and D. Stanley, "Control and
Provisioning of Wireless Access Points (CAPWAP) Protocol
Binding for IEEE 802.11", RFC 5416, March 2009.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)",
RFC 5996, September 2010.
[TR23.829]
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"3GPP TR23.829, Local IP Access and Selected IP Traffic
Offload (LIPA-SIPTO)", October 2011.
[TS23.203]
"3GPP TS23.203, Policy and Charging control architecture",
September 2012.
[TS29.212]
"3GPP TS29.212, Policy and Charging Control (PCC) over
Gx/Sd reference point", September 2012.
9.2. Informative References
[TR203] "Broadband Forum Technical Report TR-203, Interworking
between Next Generation Fixed and 3GPP Wireless Access",
August 2012.
[TS24.302]
"3GPP TS24.302, Access to the 3GPP Evolved Packet Core
(EPC) via non-3GPP access networks", September 2012.
[WT146] "Broadband Forum Working Text WT-146, Subscriber
Sessions", June 2012.
Authors' Addresses
Li Xue
Huawei
No.156 Beiqing Rd. Z-park, Shi-Chuang-Ke-Ji-Shi-Fan-Yuan,
Beijing, HaiDian District 100095
China
Email: xueli@huawei.com
Behcet Sarikaya
Huawei
5340 Legacy Dr.
Plano, TX 75024
Email: sarikaya@ieee.org
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Dirk von Hugo
Telekom Innovation Laboratories
Deutsche-Telekom-Allee 7
D-64295 Darmstadt
Germany
Email: Dirk.von-Hugo@telekom.de
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