Internet DRAFT - draft-ietf-v6ops-ipv6-roaming-analysis
draft-ietf-v6ops-ipv6-roaming-analysis
Network Working Group G. Chen
Internet-Draft H. Deng
Intended status: Informational China Mobile
Expires: April 22, 2015 D. Michaud
Rogers Communications
J. Korhonen
Broadcom
M. Boucadair
France Telecom
A. Vizdal
Deutsche Telekom AG
October 19, 2014
Analysis of Failure Cases in IPv6 Roaming Scenarios
draft-ietf-v6ops-ipv6-roaming-analysis-07
Abstract
This document identifies a set of failure cases that may be
encountered by IPv6-enabled mobile customers in roaming scenarios.
The analysis reveals that the failure causes include improper
configurations, incomplete functionality support in equipment, and
inconsistent IPv6 deployment strategies between the home and the
visited networks.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 22, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Roaming Architecture: An Overview . . . . . . . . . . . . 4
2.1.1. Home Routed Mode . . . . . . . . . . . . . . . . . . 4
2.1.2. Local Breakout Mode . . . . . . . . . . . . . . . . . 5
2.2. Typical Roaming Scenarios . . . . . . . . . . . . . . . . 6
3. Failure Case in the Network Attachment . . . . . . . . . . . 7
4. Failure Cases in the PDP/PDN Creation . . . . . . . . . . . . 8
4.1. Case 1: Splitting Dual-stack Bearer . . . . . . . . . . . 9
4.2. Case 2: IPv6 PDP/PDN Unsupported . . . . . . . . . . . . 10
4.3. Case 3: Inappropriate Roaming APN Set . . . . . . . . . . 11
4.4. Case 4: Fallback Failure . . . . . . . . . . . . . . . . 11
5. Failure Cases in the Service Requests . . . . . . . . . . . . 11
5.1. Lack of IPv6 Support in Applications . . . . . . . . . . 11
5.2. 464xlat Support . . . . . . . . . . . . . . . . . . . . . 12
6. HLR/HSS User Profile Setting . . . . . . . . . . . . . . . . 12
7. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 14
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9. Security Considerations . . . . . . . . . . . . . . . . . . . 15
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
Many Mobile Operators have deployed IPv6, or are about to, in their
operational networks. A customer in such a network can be provided
IPv6 connectivity if their User Equipment (UE) is IPv6-compliant.
Operators may adopt various approaches to deploy IPv6 in mobile
networks such as the solutions described in [TR23.975]). Depending
on network conditions, either dual-stack or IPv6-only deployment
schemes can be enabled.
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A detailed overview of IPv6 support in 3GPP architectures is provided
in [RFC6459].
It has been observed and reported that a mobile subscriber roaming
around a different operator's areas may experience service disruption
due to inconsistent configurations and incomplete functionality of
equipment in the network. This document focuses on these issues.
1.1. Terminology
This document makes use of these terms:
o Mobile networks refer to 3GPP mobile networks.
o Mobile UE denotes a 3GPP device which can be connected to 3GPP
mobile networks.
o The Public Land Mobile Network (PLMN) is a network that is
operated by a single administrative entity. A PLMN (and therefore
also an operator) is identified by the Mobile Country Code (MCC)
and the Mobile Network Code (MNC). Each (telecommunications)
operator providing mobile services has its own PLMN [RFC6459].
o The Home Location Register (HLR) is a pre-Release-5 database (but
is also used in Release-5 and later networks in real deployments)
that contains subscriber data and information related to call
routing. All subscribers of an operator and the subscribers'
enabled services are provisioned in the HLR [RFC6459].
o The Home Subscriber Server (HSS) is a database for a given
subscriber and was introduced in 3GPP Release-5. It is the entity
containing the subscription-related information to support the
network entities actually handling calls/sessions [RFC6459].
"HLR/HSS" is used collectively for the subscriber database unless
referring to the failure case related to General Packet Radio Service
(GPRS) Subscriber data from the HLR.
An overview of key 3GPP functional elements is documented in
[RFC6459].
"Mobile device" and "mobile UE" are used interchangeably.
2. Background
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2.1. Roaming Architecture: An Overview
Roaming occurs in two scenarios:
o International roaming: a mobile UE enters a visited network
operated by a different operator, where a different Public Land
Mobile Network (PLMN) code is used. The UEs could, either in an
automatic mode or in a manual mode, attach to the visited PLMN.
o Intra-PLMN mobility: an operator may have one or multiple PLMN
codes. A mobile UE could pre-configure the codes to identify the
Home PLMN (HPLMN) or Equivalent HPLMN (EHPLMN). Intra-PLMN
mobility allows the UE moving to a different area of HPLMN and
EHPLMN. When the subscriber profile is not stored in the visited
area, HLR/HSS in the Home area will transmit the profile to
Serving GPRS Support Node (SGSN)/Mobility Management Entity (MME)
in the visited area so as to complete network attachment.
When a UE is turned on or is transferred via a hand-over to a visited
network, the mobile device will scan all radio channels and find
available PLMNs to attach to. The SGSN or the MME in the visited
networks must contact the HLR or HSS to retrieve the subscriber
profile.
Steering of roaming may also be used by the HPLMN to further restrict
which of the available networks the UE may be attached to. Once the
authentication and registration stage is completed, the Packet Data
Protocol (PDP) or Packet Data Networks (PDN) activation and traffic
flows may be operated differently according to the subscriber profile
stored in the HLR or the HSS.
The following sub-sections describe two roaming modes: Home routed
traffic (Section 2.1.1) and Local breakout (Section 2.1.2).
2.1.1. Home Routed Mode
In this mode, the subscriber's UE gets IP addresses from the home
network. All traffic belonging to that UE is therefore routed to the
home network (Figure 1).
GPRS roaming exchange (GRX) or Internetwork Packet Exchange (IPX)
networks [IR.34] are likely to be invoked as the transit network to
deliver the traffic. This is the main mode for international roaming
of Internet data services to facilitate the charging process between
the two involved operators.
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+-----------------------------+ +------------------------+
|Visited Network | |Home Network |
| +----+ +--------+ | (GRX/IPX) | +--------+ Traffic Flow
| | UE |=======>|SGSN/MME|====================>|GGSN/PGW|============>
| +----+ +--------+ | Signaling | +--------+ |
| |------------------------>+--------+ |
| | | |HLR/HSS | |
| | | +--------+ |
+-----------------------------+ +------------------------+
Figure 1: Home Routed Traffic
2.1.2. Local Breakout Mode
In the local breakout mode, IP addresses are assigned by the visited
network to a roaming mobile UE. Unlike the home mode, the traffic
doesn't have to traverse GRX/IPX; it is offloaded locally at a
network node close to that device's point of attachment in the
visited network. This mode ensures a more optimized forwarding path
for the delivery of packets belonging to a visiting UE (Figure 2).
+----------------------------+ +----------------+
|Visited Network | |Home Network |
| +----+ +--------+ | Signaling | +--------+ |
| | UE |=======>|SGSN/MME|------------------->|HLR/HSS | |
| +----+ +--------+ | (GRX/IPX) | +--------+ |
| || | | |
| +--------+ | | |
| |GGSN/PGW| | | |
| +--------+ | | |
| Traffic Flow || | | |
+--------------------||------+ +----------------+
\/
Figure 2: Local Breakout
The international roaming of IP Multimedia Subsystem (IMS) based
services, e.g., Voice over LTE (VoLTE)[IR.92], is claimed to select
the local breakout mode in [IR.65]. Data service roaming across
different areas within an operator network might use local breakout
mode in order to get more efficient traffic forwarding and also ease
emergency services. The local breakout mode could also be applied to
an operator's alliance for international roaming of data service.
EU Roaming Regulation III [EU-Roaming-III] involves local breakout
mode allowing European subscribers roaming in European 2G/3G networks
to have their Internet data routed directly to the Internet from
their current VPLMN.
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Specific local breakout-related configuration considerations are
listed below:
o Operators may add the APN-OI-Replacement flag defined in 3GPP
[TS29.272] into the user's subscription-data. The visited network
indicates a local domain name to replace the user requested Access
Point Name (APN). Consequently, the traffic would be steered to
the visited network. Those functions are normally deployed for
the intra-PLMN mobility cases.
o Operators may also configure the VPLMN-Dynamic-Address-Allowed
flag [TS29.272] in the user's profile to enable local breakout
mode in Visited Public Land Mobile Networks (VPLMNs).
o 3GPP specified Selected IP Traffic Offload (SIPTO) function
[TS23.401] since Release 10 in order to get efficient route paths.
It enables an operator to offload a portion of the traffic at a
network node close to the visiting UE's point of attachment to the
visited network.
o GSMA has defined Roaming Architecture for Voice over LTE with
Local Breakout (RAVEL) [IR.65] as the IMS international roaming
architecture. Local breakout mode has been adopted for the IMS
roaming architecture.
2.2. Typical Roaming Scenarios
Three stages occur when a subscriber roams to a visited network and
intends to invoke services:
o Network attachment: this occurs when the UE enters a visited
network. During the attachment phase, the visited network should
authenticate the subscriber and make a location update to the HSS/
HLR in the home network of the subscriber. Accordingly, the
subscriber profile is offered from the HSS/HLR. The subscriber
profile contains the allowed Access Point Names (APN), the allowed
PDP/PDN Types and rules regarding the routing of data sessions
(i.e., home routed or local breakout mode) [TS29.272]. The SGSN/
MME in the visited network can use this information to facilitate
the subsequent PDP/PDN session creation.
o PDP/PDN context creation: this occurs after the subscriber UE has
been successfully attached to the network. This stage is
integrated with the attachment stage in the case of 4G, but is a
separate process in 2/3G. 3GPP specifies three types of PDP/PDN to
describe connections, i.e., PDP/PDN Type IPv4, PDP/PDN Type IPv6
and PDP/ PDN Type IPv4v6. When a subscriber creates a data
session, their device requests a particular PDP/PDN Type. The
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allowed PDP/PDN types for that subscriber are learned in the
attachment stage. Hence, SGSN/MME could initiate PDP/PDN request
to GGSN/PGW modulo subscription grants.
o Service requests: when the PDP/PDN context is created
successfully, UEs may launch applications and request services
based on the allocated IP addresses. The service traffic will be
transmitted via the visited network.
Failures that occur at the attachment stage (Section 3) are
independent of home routed and the local breakout mode. Most failure
cases in the PDP/PDN context creation (Section 4) and service
requests (Section 5) occur in the local breakout mode.
3. Failure Case in the Network Attachment
3GPP specified PDP/PDN type IPv4v6 in order to allow a UE get both an
IPv4 address and an IPv6 prefix within a single PDP/PDN bearer. This
option is stored as a part of subscription data for a subscriber in
the HLR/HSS. PDP/PDN type IPv4v6 has been introduced at the
inception of Evolved Packet System (EPS) in 4G networks.
The nodes in 4G networks should present no issues with the handling
of this PDN type. However, the level of support varies in 2/3G
networks depending on SGSN software version. In theory, S4-SGSN
(i.e., an SGSN with S4 interface) supports the PDP/PDN type IPv4v6
since Release 8 and a Gn-SGSN (i.e., the SGSN with Gn interface)
supports it since Release 9. In most cases, operators normally use
Gn-SGSN to connect either GGSN in 3G or Packet Data Network Gateway
(PGW) in 4G.
The MAP (Mobile Application Part) protocol, as defined in 3GPP
[TS29.002], is used over the Gr interface between SGSN and HLR. The
MAP Information Element (IE) "ext-pdp-Type" contains the IPv4v6 PDP
Type that is conveyed to SGSN from the HLR within the Insert
Subscriber Data (ISD) MAP operation. If the SGSN does not support
the IPv4v6 PDP Type, it will not support the "ext-pdp-Type" IE and
consequently it must silently discard that IE and continue processing
of the rest of the ISD MAP message. An issue that has been observed
is that multiple SGSNs are unable to correctly process a subscriber's
data received in the Insert Subscriber Data Procedure [TS23.060]. As
a consequence, it will likely discard the subscriber attach request.
This is erroneous behavior due to the equipment not being compliant
with 3GPP Release 9.
In order to avoid encountering this attach problem at a visited SGSN,
both operators should make a comprehensive roaming agreement to
support IPv6 and ensure that it aligns with the GSMA documents, e.g.,
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[IR.33], [IR.88] and [IR.21]. Such an agreement requires the visited
operator to get the necessary patch on all its SGSN nodes to support
the "ext-pdp-Type" MAP IE sent by the HLR. To ensure data session
continuity in Radio Access Technology (RAT) handovers the PDN Type
sent by the HSS to the MME could be consistent with the PDP Type sent
by the HLR to the Gn-SGSN. Where roaming agreements and visited SGSN
nodes have not been updated, the HPLMN also has to make use of
specific implementations (not standardized by 3GPP, discussed further
in Section 6) in the HLR/HSS of the home network. That is, when the
HLR/HSS receives an Update Location message from a visited SGSN not
known to support dual-stack in a single bearer, subscription data
allowing only PDP/PDN type IPv4 or IPv6 will be sent to that SGSN in
the Insert Subscriber Data procedure. This guarantees that the user
profile is compatible with the visited SGSN/MME capability. In
addition, HSS may not have to change, if the PGW is aware of
subscriber's roaming status and only restricts the accepted PDN type
consistent with PDP type sent by the HLR. For example, an AAA server
may coordinate with the PGW to decide the allowed PDN type.
Alternatively, HPLMNs without the non-standardized capability to
suppress the sending of "ext-pdp-Type" by the HLR may have to remove
this attribute from APNs with roaming service. PDN Type IPv4v6 must
also be removed from the corresponding profile for the APN in the
HSS. This will restrict their roaming UEs to only IPv4 or IPv6 PDP/
PDN activation. This alternative has problems:
o The HPLMN cannot support dual-stack in a single bearer at home
either where the APN profile in the HLR/HSS is also used for
roaming.
o The UE may set-up separate parallel bearers for IPv4 and IPv6
where only single stack IPv4 or IPv6 service is preferred by the
operator.
4. Failure Cases in the PDP/PDN Creation
When a subscriber's UE succeeds in the attach stage, the IP
allocation process takes place to retrieve IP addresses. In general,
a PDP/PDN type IPv4v6 request implicitly allows the network side to
make several IP assignment options, including IPv4-only, IPv6-only,
IPv4 and IPv6 in single PDP/PDN bearer, IPv4 and IPv6 in separated
PDP/PDN bearers.
A PDP/PDN type IPv4 or IPv6 restricts the network side to only
allocate requested IP address family.
This section summarizes several failures in the Home Routed (HR) and
Local Breakout (LBO) mode as shown in Table 1.
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+-------+-------------+------------------------+---------+
| Case# | UE request | PDP/PDN IP Type | Mode |
| | | permitted on GGSN/PGW | |
+-------+-------------+------------------------+---------+
| | IPv4v6 | IPv4v6 | HR |
| #1 |-------------+------------------------+---------+
| | IPv4v6 | IPv4 or IPv6 | LBO |
+-------+-------------+------------------------+---------+
| #2 | IPv6 | IPv6 | HR |
+-------+-------------+------------------------+---------+
| #3 | IPv4 | IPv6 | HR |
+-------+-------------+------------------------+---------+
| #4 | IPv6 | IPv4 | LBO |
+-------+-------------+------------------------+---------+
Table 1: Failure Cases in the PDP/PDN Creation
4.1. Case 1: Splitting Dual-stack Bearer
Dual-stack capability is provided using separate PDP/PDN activation
in the visited network that doesn't support PDP/PDN type IPv4v6.
That means only separate parallel single-stack IPv4 and IPv6 PDP/PDN
connections are allowed to be initiated to separately allocate an
IPv4 address and an IPv6 prefix. The SGSN does not support the Dual
Address Bearer Flag (DAF) or does not set DAF because the operator
uses single addressing per bearer to support interworking with nodes
of earlier releases. Regardless of home routed or local breakout
mode, GGSN/PGW will change PDN/PDP type to a single address PDP/PDN
type and return the Session Management (SM) Cause #52 "Single address
bearers only allowed" or SM Cause #28 "Unknown PDP address or PDP
type" as per [TS24.008] and [TS24.301] to the UE. In this case, the
UE may make another PDP/PDN request with a single address PDP type
(IPv4 or IPv6) other than the one already activated.
This approach suffers from the followings drawbacks:
o The parallel PDP/PDN activation would likely double PDP/PDN bearer
resource on the network side and Radio Access Bearer (RAB)
resource on the RAN side. It also impacts the capacity of the
GGSN/PGW, since only a certain amount of PDP/PDN activation is
allowed on those nodes.
o Some networks may only allow one PDP/PDN be alive for each
subscriber. For example, an IPv6 PDP/PDN will be rejected if the
subscriber has an active IPv4 PDP/PDN. Therefore, the subscriber
would not be able to obtain the IPv6 connection in the visited
network. It is even worse as they may have a risk of losing all
data connectivity if the IPv6 PDP gets rejected with a permanent
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error at the APN-level and not an error specific to the PDP-Type
IPv6 requested.
o Additional correlations between those two PDP/PDN contexts are
required on the charging system.
o Policy and Charging Rules Function (PCRF) [TS29.212]/ Policy and
Charging Enforcement Function (PCEF) treats the IPv4 and IPv6
session as independent and performs different Quality of Service
(QoS) policies. The subscriber may have unstable experiences due
to different behaviors on each IP version connection.
o Mobile devices may have a limitation on allowed simultaneous PDP/
PDN contexts. Excessive PDP/PDN activation may result in service
disruption.
In order to avoid the issue, the roaming agreement in the home routed
mode should make sure the visited SGSN supports and set the DAF.
Since the PDP/PDN type IPv4v6 is supported in the GGSN/PGW of home
network, it's expected that the visited SGSN/MME could create dual-
stack bearer as UE requested.
In the local breakout mode, the visited SGSN may only allow single IP
version addressing. In this case, DAF on visited SGSN/MME has to be
unset. One approach is to set a dedicated Access Point Name (APN)
[TS23.003] profile to only request PDP/PDN type IPv4 in the roaming
network. Some operators may also consider not adopting the local
breakout mode to avoid the risks.
4.2. Case 2: IPv6 PDP/PDN Unsupported
PDP/PDN type IPv6 has good compatibility to visited networks during
the network attachment. In order to support the IPv6-only visitors,
SGSN/MME in the visited network is required to accept IPv6-only PDP/
PDN activation requests and enable IPv6 on user plane towards the
home network.
In some cases, IPv6-only visitors may still be subject to the SGSN
capability in visited networks. This becomes especially risky if the
home operator performs roaming steering targeted to an operator that
doesn't allow IPv6. The visited SGSN may just directly reject the
PDP context activation. Therefore, it's expected that visited
network is IPv6 roaming-friendly to enable the functions on SGSN/MME
by default. Otherwise, operators may consider steering the roaming
traffic to the IPv6-enable visited network that has IPv6 roaming
agreement.
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4.3. Case 3: Inappropriate Roaming APN Set
If IPv6 single stack with the home routed mode is deployed, the
requested PDP/PDN type should also be IPv6. Some implementations
that support roaming APN profile may set IPv4 as the default PDP/PDN
type, since the visited network is incapable of supporting PDP/PDN
types IPv4v6 (Section 4.1) and IPv6 (Section 4.2). The PDP/PDN
request will fail because the APN in the home network only allows
IPv6. Therefore, the roaming APN have to be compliant with the home
network configuration when home routed mode is adopted.
4.4. Case 4: Fallback Failure
In the local breakout mode, PDP/PDN type IPv6 should have no issues
to pass through network attachment process, since 3GPP specified the
PDP/PDN type IPv6 as early as PDP/PDN type IPv4. When a visitor
requests PDP/PDN type IPv6, the network should only return the
expected IPv6 prefix. The UE may fail to get an IPv6 prefix if the
visited network only allocates an IPv4 address. In this case, the
visited network will reject the request and send the cause code to
the UE.
A proper fallback scheme for PDP/PDN type IPv6 is desirable, however
there is no standard way to specify this behavior. Roaming APN
profile could help to address the issue by setting PDP/PDN type IPv4.
For instance, the Android system solves the issue by configuring the
roaming protocol to IPv4 for the Access Point Name (APN). It
guarantees that UE will always initiate a PDP/PDN type IPv4 in the
roaming area.
5. Failure Cases in the Service Requests
After the successful network attachment and IP address allocation,
applications could start to request service based on the activated
PDP/PDN context. The service request may depend on specific IP
family or network collaboration. If traffic is offloaded locally
(Section 2.1.2 ), the visited network may not be able to accommodate
UE's service requests. This section describes the failures.
5.1. Lack of IPv6 Support in Applications
Operators may only allow IPv6 in the IMS APN. VoLTE [IR.92] or Rich
Communication Suite (RCS) [RCC.07] use the APN to offer the voice
service for visitors. The IMS roaming in RAVEL architecture [IR.65]
offloads voice and video traffic in the visited network, therefore a
dual-stack visitor can only be assigned with an IPv6 prefix but no
IPv4 address. If the applications can't support IPv6, the service is
likely to fail.
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Translation-based methods, for example 464xlat [RFC6877] or Bump-in-
the-host (BIH) [RFC6535], may help to address the issue if there are
IPv6 compatibility problems. The translation function could be
enabled in an IPv6-only network and disabled in a dual-stack or IPv4
network, therefore the IPv4 applications only get the translation in
the IPv6 network and perform normally in an IPv4 or dual-stack
network.
5.2. 464xlat Support
464xlat[RFC6877] is proposed to address the IPv4 compatibility issue
in an IPv6-only connectivity environment. The customer-side
translator (CLAT) function on a mobile device is likely used in
conjunction with a PDP/PDN IPv6 type request and cooperates with a
remote NAT64 [RFC6146] device.
464xlat may use the mechanism defined in [RFC7050] or [RFC7225] to
detect the presence of NAT64 devices and to learn the IPv6 prefix
used for protocol translation[RFC6052].
In the local breakout approach, when a UE with the 464xlat function
roaming on an IPv6 visited network may encounter various situations.
For example, the visited network may not deploy DNS64 [RFC6147] but
only NAT64, CLAT may not be able to discover the provider-side
translator (PLAT) translation IPv6 prefix used as a destination of
the PLAT. If the visited network doesn't deploy NAT64 and DNS64,
464xlat can't perform successfully due to the lack of PLAT
collaboration. Even in the case of the presence of NAT64 and DNS64,
pre-configured PLAT-side IPv6 prefix in the CLAT may cause the
failure because it can't match the PLAT translation.
Considering the various network's situations, operators may turn off
local breakout and use the home routed mode to perform 464xlat.
Alternatively, UE may support the different roaming profile
configurations to adopt 464xlat in the home networks and use
IPv4-only in the visited networks.
6. HLR/HSS User Profile Setting
A proper user profile configuration would provide a deterministic
outcome to the PDP/PDN creation stage where dual-stack, IPv4-only and
IPv6-only connectivity requests may come from devices. The HLR/HSS
may have to apply extra logic (not standardized by 3GPP) to achieve
this. It is also desirable that the network could set-up
connectivity of any requested PDP/PDN context type.
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The following are examples to illustrate the settings for the
scenarios and decision criteria to apply when returning user profile
information to the visited SGSN.
user profile #1:
PDP-Context ::= SEQUENCE {
pdp-ContextId ContextId,
pdp-Type PDP-Type-IPv4
....
ext-pdp-Type PDP-Type-IPv4v6
...
}
user profile #2:
PDP-Context ::= SEQUENCE {
pdp-ContextId ContextId,
pdp-Type PDP-Type-IPv6
....
}
Scenario 1: Support of IPv6-only, IPv4-only and dual-stack devices.
The full PDP-context parameters are referred to Section 17.7.1
"Mobile Service date types" of [TS29.002]. User profiles #1 and #2
share the same "ContextId". The setting of user profile #1 enables
IPv4-only and dual-stack devices to work. And, the user profile #2
fulfills the request if the device asks for IPv6 only PDP context.
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user profile #1:
PDP-Context ::= SEQUENCE {
pdp-ContextId ContextId,
pdp-Type PDP-Type-IPv4
....
ext-pdp-Type PDP-Type-IPv4v6
...
}
user profile #2:
PDP-Context ::= SEQUENCE {
pdp-ContextId ContextId,
pdp-Type PDP-Type-IPv4
....
}
Scenario 2: Support of dual-stack devices with pre-R9 vSGSN access.
User profiles #1 and #2 share the same "ContextId". If a visited
SGSN is identified as early as pre-Release 9, the HLR/HSS should only
send user profile#2 to the visited SGSN.
7. Discussion
Several failure cases have been discussed in this document. It has
been illustrated that the major problems happen at three stages,
i.e., the initial network attachment, the PDP/PDN creation and
service requests.
In the network attachment stage, PDP/PDN type IPv4v6 is the major
concern to the visited pre-Release 9 SGSN. 3GPP didn't specify PDP/
PDN type IPv4v6 in the earlier releases. That PDP/PDN type is
supported in new-built EPS network, but isn't supported well in the
third generation network. Visited SGSNs may discard the subscriber's
attach requests because the SGSN is unable to correctly process PDP/
PDN type IPv4v6. Operators may have to adopt temporary solutions
unless all the interworking nodes (i.e., the SGSN) in the visited
network have been upgraded to support the ext-PDP-Type feature.
In the PDP/PDN creation stage, PDP/PDN types IPv4v6 and IPv6 support
on the visited SGSN is the major concern. It has been observed that
IPv6 single stack with the home routed mode is a viable approach to
deploy IPv6. It is desirable that the visited SGSN could enable IPv6
on the user plane by default. For support of the PDP/PDN type
IPv4v6, it is suggested to set the DAF. As a complementary function,
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the implementation of roaming APN configuration is useful to
accommodate the visited network. However, it should consider roaming
architecture and permitted PDP/PDN type to make proper setting on the
UE. Roaming APN in the home routed mode is recommended to align with
home network profile setting. In the local breakout case, PDP/PDN
type IPv4 could be selected as a safe way to initiate PDP/PDN
activation.
In the service requests stage, the failure cases mostly occur in the
local breakout case. The visited network may not be able to satisfy
the requested capability from applications or UEs. Operators may
consider using home routed mode to avoid these problems. Several
solutions either in the network side or mobile device side can also
help to address the issue. For example,
o 464xlat could help IPv4 applications access IPv6 visited networks.
o Networks can deploy an AAA server to coordinate the mobile device
capability. Once the GGSN/PGW receives the session creation
request, it will initiate an Access-Request to an AAA server in
the home network via the RADIUS protocol. The Access-Request
contains subscriber and visited network information, e.g., PDP/PDN
Type, International Mobile Equipment Id (IMEI), Software Version
(SV) and visited SGSN/MME location code, etc. The AAA server
could take mobile device capability and combine it with the
visited network information to ultimately determine the type of
session to be created, i.e., IPv4, IPv6 or IPv4v6.
8. IANA Considerations
This document makes no request of IANA.
9. Security Considerations
Although this document defines neither a new architecture nor a new
protocol, the reader is encouraged to refer to [RFC6459] for a
generic discussion on IPv6-related security considerations.
10. Acknowledgements
Many thanks to F. Baker and J. Brzozowski for their support.
This document is the result of the IETF v6ops IPv6-Roaming design
team effort.
The authors would like to thank Mikael Abrahamsson, Victor Kuarsingh,
Heatley Nick, Alexandru Petrescu, Tore Anderson, Cameron Byrne,
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Holger Metschulat and Geir Egeland for their helpful discussions and
comments.
The authors especially thank Fred Baker and Ross Chandler for their
efforts and contributions which substantially improved the
readability of the document.
11. References
11.1. Normative References
[IR.21] Global System for Mobile Communications Association,
GSMA., "Roaming Database, Structure and Updating
Procedures", July 2012.
[IR.65] Global System for Mobile Communications Association,
GSMA., "IMS Roaming & Interworking Guidelines", May 2012.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, April 2011.
[RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van
Beijnum, "DNS64: DNS Extensions for Network Address
Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
April 2011.
[RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
Combination of Stateful and Stateless Translation", RFC
6877, April 2013.
[TS23.060]
3rd Generation Partnership Project, 3GPP., "General Packet
Radio Service (GPRS); Service description; Stage 2 v9.00",
March 2009.
[TS23.401]
3rd Generation Partnership Project, 3GPP., "General Packet
Radio Service (GPRS) enhancements for Evolved Universal
Terrestrial Radio Access Network (E-UTRAN) access v9.00",
March 2009.
[TS29.002]
3rd Generation Partnership Project, 3GPP., "Mobile
Application Part (MAP) specification v9.12.0", December
2009.
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[TS29.272]
3rd Generation Partnership Project, 3GPP., "Mobility
Management Entity (MME) and Serving GPRS Support Node
(SGSN) related interfaces based on Diameter protocol
v9.00", September 2009.
11.2. Informative References
[EU-Roaming-III]
"http://www.amdocs.com/Products/Revenue-
Management/Documents/
amdocs-eu-roaming-regulation-III-solution.pdf", July 2013.
[IR.33] Global System for Mobile Communications Association,
GSMA., "GPRS Roaming Guidelines", July 2012.
[IR.34] Global System for Mobile Communications Association,
GSMA., "Guidelines for IPX Provider networks", November
2013.
[IR.88] Global System for Mobile Communications Association,
GSMA., "LTE Roaming Guidelines", January 2012.
[IR.92] Global System for Mobile Communications Association
(GSMA), , "IMS Profile for Voice and SMS Version 7.0",
March 2013.
[RCC.07] Global System for Mobile Communications Association
(GSMA), , "Rich Communication Suite 5.1 Advanced
Communications Services and Client Specification Version
4.0", November 2013.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
[RFC6459] Korhonen, J., Soininen, J., Patil, B., Savolainen, T.,
Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
Partnership Project (3GPP) Evolved Packet System (EPS)",
RFC 6459, January 2012.
[RFC6535] Huang, B., Deng, H., and T. Savolainen, "Dual-Stack Hosts
Using "Bump-in-the-Host" (BIH)", RFC 6535, February 2012.
[RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
the IPv6 Prefix Used for IPv6 Address Synthesis", RFC
7050, November 2013.
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[RFC7225] Boucadair, M., "Discovering NAT64 IPv6 Prefixes Using the
Port Control Protocol (PCP)", RFC 7225, May 2014.
[TR23.975]
3rd Generation Partnership Project, 3GPP., "IPv6 migration
guidelines", June 2011.
[TS23.003]
3rd Generation Partnership Project, 3GPP., "Numbering,
addressing and identification v9.0.0", September 2009.
[TS24.008]
3rd Generation Partnership Project, 3GPP., "Mobile radio
interface Layer 3 specification; Core network protocols;
Stage 3 v9.00", September 2009.
[TS24.301]
3rd Generation Partnership Project, 3GPP., "Non-Access-
Stratum (NAS) protocol for Evolved Packet System (EPS) ;
Stage 3 v9.00", September 2009.
[TS29.212]
3rd Generation Partnership Project, 3GPP., "Policy and
Charging Control (PCC); Reference points v9.0.0",
September 2009.
Authors' Addresses
Gang Chen
China Mobile
53A,Xibianmennei Ave.,
Xuanwu District,
Beijing 100053
China
Email: phdgang@gmail.com
Hui Deng
China Mobile
53A,Xibianmennei Ave.,
Xuanwu District,
Beijing 100053
China
Email: denghui@chinamobile.com
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Dave Michaud
Rogers Communications
8200 Dixie Rd.
Brampton, ON L6T 0C1
Canada
Email: dave.michaud@rci.rogers.com
Jouni Korhonen
Broadcom
Porkkalankatu 24
FIN-00180 Helsinki, Finland
Email: jouni.nospam@gmail.com
Mohamed Boucadair
France Telecom
Rennes,
35000
France
Email: mohamed.boucadair@orange.com
Vizdal Ales
Deutsche Telekom AG
Tomickova 2144/1
Prague 4, 149 00
Czech Republic
Email: ales.vizdal@t-mobile.cz
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