Internet Area WG Praveen Muley
Internet Draft Wim Henderickx
Intended status: Informational Nokia
Expires: July 31, 2018 Geng Liang
China Mobile
Hans Liu
D-Link Corp
Loris Cardullo
Jonathan Newton
Vodafone
SungHoon Seo
Korea Telecom
Sagiv Draznin
Verizon Wireless
Basavaraj Patil
AT&T
January 31, 2018
Network based Bonding solution for Hybrid Access
draft-muley-network-based-bonding-hybrid-access-02
Abstract
In order to address increasing bandwidth demands, operators are
considering bundling of multiple heterogeneous access networks
(Hybrid access) for residential and enterprise customers. This
document describes a solution for Hybrid access and covers the use
case scenarios.
Requirements Language
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].
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/.
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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 July 31, 2018.
Copyright Notice
Copyright (c) 2018 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
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. Terminology....................................................3
3. Reference Architecture.........................................4
4. Network Based Bonding Solution Overview........................5
4.1. Separate BNG and PGW......................................5
4.2. Integrated BNG and SGW/PGW................................6
5. HAG Function...................................................7
5.1. Address Assignment........................................7
5.1.1. Separate BNG and PGW.................................7
5.1.2. Integrated BNG and SGW/PGW...........................8
5.2. Setup and Tunnel Management...............................9
5.3. Traffic distribution policies............................10
5.4. Path Management..........................................11
5.5. Backward compatibility...................................12
6. Applicability in Mobile networks..............................12
7. Inter-working with MP-TCP.....................................14
8. Security Considerations.......................................14
9. IANA considerations...........................................15
10. References...................................................15
10.1. Normative References....................................15
10.2. Informative References..................................15
11. Acknowledgments..............................................16
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1. Introduction
To address the increasing demand of bandwidth by residential and
enterprise customers, operators are looking for alternatives that
can avoid rebuilding of the existing fixed access networks.
In Hybrid Access network, a Customer Premise Equipment
(CPE) is connected to heterogeneous access networks (e.g. DSL, LTE
etc) simultaneously. Traffic is distributed in flexible manner over
these heterogeneous links thus increasing the bandwidth capacity of
a residential or an enterprise customer.
This document describes a solution to implement the
network based bonding Hybrid Access architecture. The solution is
generic enough that it is applicable to fixed as well mobile nodes
with multiple Access technologies.
2. Terminology
All mobility related terms are to be interpreted as defined in
[RFC5213] and [RFC5844]. Additionally, this document uses the
following terms
IFOM IP flow mobility
NB-IFOM Network based IFOM
ePDG Evolved Packet Data Gateway (defined in 3GPP [24.302])
RR Routing Rule
HAG Hybrid Access Gateway
PcRF Policy and Charging Rules Function
NBF Network based Bonding Function
MCP Multi-path conversion point (defined in [NAMPTCP])
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3. Reference Architecture
+----+ ------
| | / \
|HOST| +-----+ | Wireless +-----\+-----+
| +-----+ | +-+ 3G/4G | | | *****
+----+ Wireless +-+ \ / | | ** **
| | ------ | | * *
+----+ | CPE | | HAG +---* Internet *
| | | | ------ | | * *
|HOST+-----+ +-+ / \ | | ** **
| |Wired| | +-+ | | | *****
+----+ +-----+ | Fixed +-----/+-----+
\ /
------
Figure 1 Network based bonding Hybrid Access Architecture
A CPE with HAG Figure 1 shows the network based bonding hybrid
access architecture. In this architecture, HAG with network bonding
function is deployed at the remote side of the CPE. The HAG receives
the downstream traffic from internet and can apply the policies to
distribute downstream traffic towards the CPE over available paths.
An in-band control protocol between the CPE and the
HAG MAY be used to negotiate the traffic distribution policies for
uplink traffic.
However, there SHOULD be flexibility to download the
traffic distribution policies OUT-of-band.
Traffic distribution policies on CPE and HAG can have
independent packet-based behavior.
Operators can have flexibility to distribute flows over
multiple paths or associate affinity of flow to a particular access
type. Traffic policies can also be applied taking into account the
access networks link status such as latency, state etc.
Operator can also apply policy to fill one access link
first before utilizing other (MAX-FILL). Affinity to one access MAY
be due to cost or application characteristics. In this case the
distribution of traffic is adjusted dynamically based on the load.
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Behavior to adjust on moving around flows or packet is a matter of
local policy.
4. Network Based Bonding Solution Overview
4.1. Separate BNG and PGW
<--------Fixed Path-----> | <----- PMIPv6/GTP ---->|
+------+ +------+
| AAA | | PCRF |
+------+ +------+
| |
| |
+---+ _----_ +------+ _----_ +------+ ****
| | _(Fixed )_ | | _( )_ | HAG | ** **
|CPE|<==( Access )==| BNG |==( Operator )==|(NBF/ |==*Internet*
+---+ (_ _) | | (_Network_) | PGW) | ** **
^ '----' +------+ '----' +------+ ****
| DSL Access PMIPv6/GTP Tunnel ^
| |
| |
| |
| Non-3GPP access |
| =================================== |
| 3GPP Access |
| +----+ |
| +------|MME |----+ |
| | +----+ | |
| | | |
| S1-AP | | S11 |
| | | |
| +---+ +-----+ S5-c |
+=======|eNB|============| SGW |===============+
+---+ S1-u +-----+ S5-u
<----GTP----> | <---PMIPV6/GTP--->|
Figure 2 Hybrid access service in Fixed mobile convergence
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In Figure 2, CPE (either home or enterprise) is connected to
internet via fixed access network using DSL as well as wireless
access network using 4G cellular network.
The fixed access network BNG is connected to the
PGW using 3GPP s2b reference point [TS23401]. The 4G cellular
network is connected to the same PGW using S5 reference point (GPRS
Tunneling Protocol (GTP) or Proxy Mobile IPV6 (PMIPV6) [RFC5213]) as
specified by the 3GPP system architecture [TS23401].
The 3GPP as well non-3GPP access is bonded in CPE
and the HAG which consist of NBF and PGW function. The bonding at
HAG is achieved by allocating the same "IP address" when LTE access
is setup on s5 and fixed (DSL) access over s2b.
The packet distribution policies applied to the bonded
session on the HAG and CPE. Policies applied on HAG helps steering
downlink traffic on specific access type or distribute percentage of
traffic across both access types on per flow basis or per packet
basis. Similarly policies applied CPE helps steering uplink traffic
on specific access type or distribute percentage of traffic on per
flow basis or per packet basis.
4.2. Integrated BNG and SGW/PGW
<----------------Fixed Path-------------->
+------+ +------+
| AAA | | PCRF |
+------+ +------+
|---------- |
|
+---+ _----_ +---+ _----_ +------+ ****
|CPE| _(Fixed )_ | | _( )_ | HAG | ** **
| |<==( Access )==|SN |==( Operator )==|(S/PGW|==*Internet*
+---+ (_ _) | | (_Network_) | BNG) | ** **
^ '----' +---+ '----' +------+ ****
| DSL Access PMIPv6/GTP Tunnel
| ^ ^
| Non-3GPP access | |
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| ================================= | |
| 3GPP Access | |
| +----+ | |
| +------|MME |--------------------+ |
| | +----+ S11-c |
| | S1-AP |
| | |
| +---+ |
+=======|eNB|================================+
+---+ S1-u
<------------GTP------------>
Figure 3 Integrated BNG,SGW,PGW with HAG
In Figure 3 , CPE is connected to internet through HAG by fixed and
wireless access. HAG consist of BNG,SGW/PGW and NBF function.
HAG performs address assignment for all access types and acts as IP
anchor point for IP services.
5. HAG Function
5.1. Address Assignment
======== :::::::: =======
CPE LTE/DSL HAG
======== :::::::: =======
5.1.1. Separate BNG and PGW
Following are steps for address allocation when BNG and PGW are
separate. HAG in this case performs the NBF and PGW function.
[...CPE obtains LTE WAN IF address "A" during Pdp from HAG...]
(...CPE performs LTE attach for IMSI "X" APN "Y"...)
(...HAG allocates address "A" from APN.............)
[...CPE obtains DSL WAN IF address "A" during PPPoE from HAG...]
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(...CPE begins the PPPoE setup with BNG....................)
(...BNG authenticates the CPE .............................)
(...BNG receives all the 3GPP attributes from AAA server...)
(...BNG signals on s2b to HAG for address allocation.......)
(...HAG receives the s2b attach for APN "Y" with same IMSI.)
(...HAG finds session for IMSI "X" in APN "Y" RAT=LTE......)
(...HAG bonds the LTE session with s2b session.............)
(...HAG returns address "A" in S2b response to BNG.........)
(...BNG stitches the PPPoE session with s2b session .......)
(...BNG returns the address "A" in PPPoE/DHCP to CPE.......)
HAG performs Address assignment for all access type which acts as
anchor point for IP services.
APN "Y" on HAG is configured with property of "bonding" so that it
can accept request from another access type for the same IMSI within
same APN for same Pdp type. This helps in bonding the session with
another access type session instead of treating it as handover.
BNG performs authentication of CPE. As part of
authentication, it also receives the 3GPP attributes like IMSI, APN
and HAG information from AAA server. It uses (3GPP) S2b reference
point in [TS23402], specified by the 3GPP system architecture to get
IP address from HAG and stitches the fixed access (PPPoE/IPoE)
session with the s2b session both in control plane and data-plane.
The CPE remains unchanged as it uses standard method of IP
address management for IPv4 and IPv6, on LTE link as well as DSL
link.
5.1.2. Integrated BNG and SGW/PGW
Following are the steps for address allocation when BNG, SGW and PGW
function is integrated along with the HAG function
[...CPE obtains LTE WAN IF address "A" during Pdp from PGW/HAG...]
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(...CPE performs LTE attach for IMSI "X" APN "Y"...)
(...HAG allocates address "A" from APN.............)
[...CPE obtains DSL WAN IF address "A" during PPPoE from BNG/HAG..]
(...CPE begins the PPPoE setup with on BNG.................)
(...BNG authenticates the CPE .............................)
(...BNG receives all the 3GPP attributes from AAA server...)
(...BNG/HAG finds session for IMSI "X" in APN "Y" RAT=LTE..)
(...BNG bonds the PPPoE session with LTE session...........)
(...BNG returns the address "A" in PPPoE/DHCP to CPE.......)
Address assignment is done in the HAG for all access type which acts
as anchor point for IP services.
APN "Y" on HAG is configured with property of "bonding" so that it
can accept request from another access type for the same IMSI within
same APN for same Pdp type. This helps in bonding the session with
another access type.
BNG performs authentication of CPE. As part of
authentication, it also receives the 3GPP attributes like IMSI, APN
and PGW information from AAA server. BNG detects that the PGW is
local and hence internally bonds the fixed (PPPoE/IPoE) session with
the LTE session with the same IMSI and APN. As part of bonding it
uses the same IP allocated for the LTE session and sends back in
PPPoE response or waits for DHCP to request for the address in the
DHCP response. Traffic distribution policies are applied to the
bonded LTE and fixed (PPPoE/IPoE) session to distribute the traffic.
The CPE remains unchanged as it uses standard method of
IP address management for IPv4 and IPv6, on LTE link as well as DSL
link.
5.2. Setup and Tunnel Management
There is no extra tunnel apart from the link tunnels representing
each access used in this solution.
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Any link can be setup first. The link that sets up access tunnel
first gets the IP address from HAG. The link which comes later is
bonded in HAG with the control plane to the existing access tunnel
and the same IP address is returned to the later tunnel setup.
BNG stitches the fixed (PPPoE/IPoE) tunnel to the s2b tunnel
setup towards the HAG. As part of it, it maps the setup and tear
down event of the fixed (PPPoE/IPoE) tunnel to the s2b tunnel and
vice versa.
5.3. Traffic distribution policies
As mentioned in earlier section, traffic distribution policies for
upstream traffic is applied at CPE where as the downstream policies
are applied at HAG. Given that single IP is allocated to all access
type in this solution, it greatly helps to do flow mobility within
the accesses.
Traffic distribution can be done on per flow basis, per MP-
TCP sub-flow basis or on per packet. Flow based traffic distribution
avoids out-of-order packets resulting out of differential latencies
on each access tunnel and doesn't require buffering resources at the
CPE or HAG to re-order the packets.
Policies applied in CPE can be downloaded out-of-band using
ANDSF mechanism. Some CPEs are capable of sending initial uplink
traffic on access type using random hashing but are able to move the
flow to the access type chosen by network for the downlink traffic
of that flow. Such CPEs need zero to minimal traffic policy
configuration.
Traffic distribution policies applied at HAG for downlink
traffic distribution can help in distributing flows or packets using
hashing.
Traffic policies MUST have the flexibility to
configure the amount of percentage of traffic to be steered over a
given access type. This allows addressing the use case where
operator MAY want to send a particular type of traffic over a
specific access type (Video over DSL). In this case a video rule
with affinity of DSL access can be set to steer 100 percent of
traffic over DSL link whereas traffic matching any-any rule can be
set to steer 50% over DSL and 50 % over LTE.
Traffic policies MUST allow asymmetric affinity association of
access type for upstream and downstream traffic which allows
splitting of a flow in upstream and downstream direction. Applying
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such polices operators can use LTE for uplink where as fixed (DSL)
for downlink. Studies of such configuration have shown application
performance improvement over use same access for an application.
For the use case where a desired access link bandwidth is
filled first (MAX-FILL) and use of second link is for the bandwidth
overflow, one can use flow based or packet based approach for
traffic distribution. The desirability of preferred access can be
due to cheap access path or link characteristics for the given
application.
To fulfill this requirement, two rate Three color marker
(trTCM) can be used. Each access link uses token buckets to meter
the packets as per configuration both at CPE and the HAG. Colored
based policy is applied at CPE and HAG to steer packets to an access
based on color. For ex. Green packets are steered to DSL if that is
the preferred access, whereas yellow packets are steered over LTE
access.
If flow based distribution is used, then on reaching certain
thresholds there MUST be flexibility to move the flows from
preferred access (say DSL) to another (LTE) by changing the
percentage distribution. However, moving of FAT flows MAY result in
under utilization of preferred access link. Similarly once the
threshold drops, the traffic can be move back to preferred access by
reverting the percentage distribution.
To avoid FAT flow distribution issues, packet based
traffic distribution can be used to fully utilize the preferred
access. Packets sent over different access for the same flow can
reach out-of-order at the receiving end, due to differential
transport latencies. Hence receiving end needs buffering and re-
ordering capabilities to deliver flow packets correctly to an
application.
5.4. Path Management
This solution relies of existing mechanism of Path management for
wireless (LTE) and fixed (PPPoE/IPoE) tunnels.
In case of failure of any access tunnel the traffic MUST be
switched to the alternate available access tunnel based on the
traffic distribution policies.
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5.5. Backward compatibility
This solution does not introduce any new protocol extensions. In
this solution the CPE uses ANDSF routing rules to do the traffic
distribution downloaded off-band in the CPE.
The policies at the HAG are either local configured or downloaded
from PCRF. The existing service (ex. IPTV traffic MUST remain on DSL
access) remains untouched by configuring appropriate traffic
distribution policies. The exact configuration of those policies is
outside the scope of this document.
6. Applicability in Mobile networks
A mobile node (MN) (also called User Equipment UE) connected to a
3GPP access network specified by the 3GPP system architecture
[TS23401] is connected over the S5 reference point (Proxy Mobile
IPV6 (PMIPV6) [RFC5213] or GPRS Tunneling Protocol (GTP)) to the PGW
where the mobile node's session is anchored.
The (3GPP) S2b reference point in [TS23402], specified by
the 3GPP system architecture defines a mechanism for allowing the
mobile node (MN) attached to an "untrusted" non-3GPP IP access
network to securely connect to a 3GPP network and access IP
services. In this scenario, the mobile node establishes an IPSec ESP
tunnel [RFC4303] to the security gateway called evolved packet data
gateway (ePDG) and which in turn establishes a GPRS Tunneling
Protocol (GTP) [TS23402] or Proxy Mobile IPV6 (PMIPV6) [RFC5213]
tunnel to the packet data gateway (PGW) [TS23402] where the mobile
node's session is anchored.
The figure below shows the hybrid access figure where the
mobile node is connected to 3GPP and non-3GPP access simultaneously
getting access to IP services via a PGW.
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<---------- IKEv2/IPsec ------> | <------ PMIPv6/GTP ----->|
+------------+
| ePDG |
| +--------+ |
+---+ _----_ | | IPsec | | _----_ +-----+ ****
|MN | _( )_ | | Module | | _( )_ | HAG/| ** **
| |<=( Internet )=| +--------+ |=( Operator )=|(PGW)|-*Internet*
+---+ (_ _) | : | (_Network_) +-----+ ** **
^ '----' | +--------+ | '----' ^ ****
| IPsec Tunnel| | GTPv2 | |PMIPv6/GTP Tunnel |
| | | MAG | | |
| | +--------+ | |
| +------------+ |
| Non-3GPP access |
| ======================================= |
| 3GPP Access |
| +----+ |
| +------|MME |----+ |
| | +----+ | |
| | | |
| S1-AP | | S11 |
| | | |
| +---+ +-----+ S5-c |
+=======|eNB|============| SGW |=================+
+---+ S1-u +-----+ S5-u
<------GTP-------> | <---PMIPV6/GTP--->|
Figure 4 Hybrid access service in Mobile network
In the hybrid access architecture, an User equipment (UE) is
connected to multiple access technology at the same time. It MAY
connect to same network or different IP network based on the
operator service. A mobile node with Third Generation Partnership
Project (3GPP) access technology such as LTE, UMTS and non-3GPP
access such as WIFI having simultaneous network connections is a use
case of hybrid access in mobile networks.
As shown in Figure 4, the LTE access is bonded with the
WIFI access and the same IP address is allocated on s2b as well as
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s5 3gpp reference point. As discussed above, traffic distribution
policies can be applied to steer traffic over specific access type
or distribute over both access type to increase the bandwidth for
the mobile node.
In some mobile networks, WIFI is preferred access since
it's cheap, in that case policies described in MAX-FILL can be
applied.
In some mobile networks, mobile nodes are configured to prefer
WIFI access as local break out policy. However it's been observed
that if mobile node has LTE access as well WIFI access available and
if the mobile node connects to WIFI access over the s2b reference
point to the same PGW, the PGW treats it as 3GPP to non-3GPP access
handover and disconnecting the LTE access. But since mobile node is
configured to be always connected over LTE access, mobile node
reconnects over LTE and the PGW treats it as non-3GPP to 3GPP access
handover disconnecting the WIFI access. This results in ping-pong
effect. Since both accesses are simultaneously connected, in this
solution, it helps in addressing the ping-pong issue as well.
7. Inter-working with MP-TCP
When used flow based hashing, it is possible that a FAT flow may
cause to over congest the access link. To address FAT flow issues
operator can deploy a MCP with the NBF. Operator in that case can
apply policy to ensure the FAT flow traffic is split among small
multi-path flows which can be seamlessly moved between the access
types based on traffic distribution policies.
Inter-working helps operators in using MP-TCP for
selective traffic thus ensuring effective utilization of buffering
resources both at CPE as well as at MCP.
8. Security Considerations
The security considerations applicable while deploying the access
types independently remains same while deploying network based
bonding hybrid access architecture. This specification does not
introduce any new security vulnerabilities.
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9. IANA considerations
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, December 2005.
[24.008] 3GPP, "Technical specification Group Core Network and
Terminals: Mobile radio interface Layer 3 specification;
Core network protocols; Stage 3"
[24.301] 3GPP, "Technical specification Group Core Network and
Terminals: Non-Access-Stratum (NAS) protocol for Evolved
Packet System (EPS); Stage 3"
[NAMPTCP] M.Bouchadair et al. "draft-nam-mptcp-deployment-
considerations-00", (work in progress), October 2016
10.2. Informative References
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V.,Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
Mobile IPv6", RFC 5844, May 2010.
[TS23402] 3GPP, "Architecture enhancements for non-3GPP accesses",
.
[TS23401] 3GPP, General Packet Radio Service (GPRS) enhancements
for Evolved Universal Terrestrial Radio Access Network (E-
UTRAN) access.
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11. Acknowledgments
The authors are thankful for the detailed review and valuable
feedback provided by Guiu Fabregas and Laurent Thiebaut.
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Authors' Addresses
Praveen Muley
Nokia
805. E. Middle Field Rd.
Mountain View, CA, 94043
Email: praveen.muley@nokia.com
Wim Henderickx
Nokia
Coperniscuslaan 50
Antwerp 2018
Belgium
Email: wim.henderickx@nokia.com
Geng Liang
China Mobile
32 Xuanwumen West Street,
Xicheng District, Beijing, 100053,
China
Email: gengliang@chinamobile.com
Hans Liu
D-Link Corporation
289, Sinhu 3rd Road,
Neihu District, Taipei City, 11494,
Taiwan, R.O.C.
Email: hans_liu@dlink.com.tw
Loris Cardullo
Vodafone
Italy
Email: Loris.Cardullo@vodafone.com
Jonathan Newton
Vodafone
United Kingdom
Email: Jonathan.Newton@vodafone.com
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SungHoon Seo
Korea Telecom
South Korea
Email: sh.seo@kt.com
Sagiv Draznin
Verizon Wireless
USA
Email: Sagiv.Draznin@VerizonWireless.com
Basavaraj Patil
AT&T
2900 W. Plano Pkwy
Plano, Texas 75075
USA
Email: bp801n@att.com
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