One document matched: draft-xue-fmc-ps-02.txt
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Network Working Group L. Xue
Internet-Draft B. Sarikaya
Intended status: Informational Huawei
Expires: April 18, 2013 D. von Hugo
Telekom Innovation Laboratories
October 15, 2012
Problem Statement for Fixed Mobile Convergence
draft-xue-fmc-ps-02.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 User Equipment
identification, mobility consideration, such as mobility status
reporting in Wi-Fi network and transporting Wi-Fi link
characteristics type of considerations.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 18, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 6
3. Key Issues in Fixed Mobile Converged Interworking . . . . . . 7
4. UE identification in Fixed Broadband Network . . . . . . . . 7
5. UE Mobility in Fixed Broadband Network . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
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. The trend of offloading the traffic
to fixed broadband network is emerging. 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 the control planes of the fixed broadband
network and the mobile network.
In the FMC interworking scenario addressed here, the fixed broadband
network must partner with the mobile network to perform
authorisation, authentication, and accounting (AAA) and acquire the
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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
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,
respectively), shown in Figure 1. PCC should support for controlling
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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. UE identification in fixed broadband network
2. UE mobility status reporting in fixed broadband network
3. Transportation of UE link characteristics in fixed broadband
network.
There are many standardization issues related to FMC and protocol
extension work needed are stated in this document. 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. UE identification in Fixed Broadband Network
Nowadays, a subscriber is always provided with a single private IPv4
address at their home or small business, which should reduce the
pressure on the available public IPv4 addresses which are now
exhausted. For instance, in the fixed broadband network, each host
within the local network will be assigned a private IPv4 address,
then NA(P)T function is responsible for translating the private IPv4
address to the public IPv4 address assigned to the CPE (Customer
Premises Equipment) by operators, and vice versa.
As a result of maintaining growth of IPv4 service, private addressing
plan will require address sharing, which will cause issues for
operators, such as traffic management, QoS enforcement, etc. in the
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FMC scenarios, where the policy control must be based on the
fundamental concept of per-UE granularity. Note that ultimately,
deploying IPv6 without NA(P)T function is the only perennial way to
ease pressure on the public IPv4 address without the need for address
sharing mechanisms that give rise to the issues identified herein.
But in the interim, however, IPv4 services are also very important
for end-users, and service providers, which can not be ignored.
Consider Figure 2 where several UEs are connected to the same RG in a
fixed broadband network in an address sharing scheme. Each UE is
assigned a private IPv4 address which are shared by RG private/public
Wide Area Network (WAN) interface IPv4 address. Problems are
introduced because of address sharing via NA(P)T and UEs
identification or Host Identifier (HOST_ID) needs to be communicated
to fixed broadband network nodes such as the edge router (BNG) or
Traffic Detection function (TDF) [RFC6269].
In FMC network, it is assumed that fixed broadband network manages
the traffic in per-UE granularity. The important consideration is
that today's PCC (including QoS control and IP flow based charging)
must be based on the concept of IP Connectivity Access Network (IP-
CAN) in per-UE granularity. IP-CAN session [TS23.203] is the
association between a UE and an IP network.
Obviously, the fixed broadband network and mobile network must
support inter-operator subscribers policy exchange, this introduces a
major challenge on how to coordinate UE identification across the
operators' domains so that the mobile network can inform the suitable
policy to the serving fixed broadband access network that its mobile
user equipment (UE) is attached to so that the fixed broadband
network can provide the appropriate FMC interworking policy and
bearer control on UE's traffic.
There may be limitations with BNG implementations with respect to the
level of granularity (per-UE) of the enforcement. A key problem is
to identify offloaded traffic from a UE behind the NA(P)T embedded
into RG. There is no longer a unique IP address per UE, in addition,
the UDP port behind NA(P)T is not bound to the special UE.
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], otherwise, the
traffic that is not subject to packet inspection may bypass the TDF.
This assumption only holds if it is possible to identify individual
UEs behind NA(P)T in fixed broadband network, shown in Figure 2.
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+----+
| UE | +----+ Internet
+----+ |TDF |--->
W +----+ Mobile
+----+ i | Network
| UE | F +----+ |
+----+ i | AP | +----------+ +----------+
+----+ | & | | | | |
| UE | L | RG |----| | +-------------+ | |
+----+ i +----+ | Access |-----| Aggregation | | Edge |
+----+ n | Node | | Network |---| Router |
| UE | k | | +-------------+ | |
+----+ +----------+ +----------+
RG with
NA(P)T
Figure 2: UE's Identification in Broadband Network
As discussed before, there are many drivers for the identification of
the host or UE when an IP (v4 or v6) address is shared among several
users in the broadband network. They include efficient packet
inspection, QoS enforcement, charging. We can note that all these
functions in FMC depend on being able to identify UEs behind the
NA(P)T functionality.
There are several possibilities which provide solutions. There are
several possible IP, ICMP (both v4 and v6) or TCP/UDP protocol
extensions, discussed in [I-D.ietf-intarea-nat-reveal-analysis].
Additionally, there may be other possibilities, such as some other
new identifier to be defined as the host identifier to be passed by
the subscriber to a server such as BNG or TDF. It is difficult to
foresee which is the suitable solution, more work needs to be done.
There are also several possibilities which provide link layer
solutions. Using VLANs or link layer address/ MAC address of the UE
provide the necessary identification for the UE. Link layer
solutions to UE identification are left out of scope.
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.
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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 |/
+----+ +-----+ | |
+----------+
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 braodband 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 and NA(P)T function. Each UE is provided with a single private
IPv4 address assigned within the local network. NA(P)T in RG is
responsible for translating the private IPv4 address to the public
IPv4 address assigned by the fixed operator.
BPCF in fixed broadband network must have partnership with PCRF in
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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.
Based on the UE's mobility, problems will arise. For example, the
PCRF will download the policy to the BPCF when UE first attaches the
AP after the UE is authenticated and an IP address/prefix is
assigned. Consider the two UEs, shown in Figure 3. UE1 and UE2 are
assigned different private/public IP addresses within the local
network, IP1 and IP2 respectively. BPCF/BNG will perform the
admission control and policy enforcement on the UE1 and UE2 traffic.
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
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.
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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 which are
common to any NA(P)T application are documented in the NAT
specification [RFC2663]. 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.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)",
RFC 5996, September 2010.
[RFC6269] Ford, M., Boucadair, M., Durand, A., Levis, P., and P.
Roberts, "Issues with IP Address Sharing", RFC 6269,
June 2011.
[TR23.829]
"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.
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9.2. Informative References
[I-D.ietf-intarea-nat-reveal-analysis]
Boucadair, M., Touch, J., Levis, P., and R. Penno,
"Analysis of Solution Candidates to Reveal a Host
Identifier (HOST_ID) in Shared Address Deployments",
draft-ietf-intarea-nat-reveal-analysis-04 (work in
progress), August 2012.
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations",
RFC 2663, August 1999.
[RFC6264] Jiang, S., Guo, D., and B. Carpenter, "An Incremental
Carrier-Grade NAT (CGN) for IPv6 Transition", RFC 6264,
June 2011.
[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
Phone:
Email: Dirk.von-Hugo@telekom.de
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