Lte outbound roaming_session

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco PublicBRKSPG-2022 1
LTE Outbound Roaming
Session for PCRF
Samir Mohanty

Agenda
 Overview
 Roaming Network Architecture
 QoS in details
 PCRF Roaming Feature
 Configuring Roaming Tables
 Lab Session
 Q&A

LTE Outbound Roaming Overview
 Service to ATT LTE subscribers roaming on
another carrier’s PLMN network with compatible
LTE devices.
 Serving both 2G/3G and 4G roaming needs for
outbound LTE subscribers.
 Traffic will pass through the IXC Zone, which is a
new zone physically connected to the core zone in
the Gn VRF.

LTE Roaming Architecture

GERAN/UTRAN Roaming Architecture
with S4-SGSN

GERAN/UTRAN Roaming Architecture
with Gn/Gp SGSN connected to
PGW

Nodes, Interfaces and Protocols
Node Interface Protocol
SGW – PGW S8 GTP (GTP-C 3GPP TS 29.274 and GTP-
U 3GPP TS 29.281)
MME - HSS S6a Diameter Base Protocol (IETF RFC 3588)
and 3GPP TS 29.272)
S4-SGSN - HSS S6d Diameter Base Protocol (IETF RFC 3588)
and 3GPP TS 29.272)
Gn/Gp SGSN -
HLR
Gr MAP protocol over SS7
hPCRF - vPCRF S9 Diameter Base Protocol (IETF RFC 3588)
and 3GPP TS 29.125)

3GPP and GSMA
 3GPP Specs describe 10 ways to roam
 GSM IR.88 reduces the number to 4
 Interfaces to support:
1. S8: Inter-PLMN reference point providing user and control plane between
the Serving GW in the VPLMN and the PDN GW in the HPLMN. S8 is the
inter PLMN variant of S5. The S8 interface (GTP based) uses GTP version 1
for the User plane, and GTP version 2 for the Control plane. Nodes supporting
the S8-GTP based interface are compliant to 3GPP TS 29.274 Release 8 or
later, and 3GPP TS 29.281 Release 8 or later.
2. Gp: Inter-PLMN reference point providing user and control plane between
the SGSN in the VPLMN and the PDN GW in the HPLMN acting as a GGSN.
Gp is the inter PLMN variant of Gn.

Scenario 1: HPMN only has PGW as the gateway
for roaming, 2G/3G Access via Gp interface
NOTE: For simplicity, HSS, PCRF, and MME
are omitted in the figures.

Scenario 2: HPMN has both GGSN and PGW as
the gateway for roaming, 2G/3G Access via Gp
interface

Scenario 3: HPMN has only PGW as the gateway
for roaming, 2G/3G Access via S4/S8 interfaces.

Scenario 4: HPMN has both PGW and GGSN as
the gateway for roaming, 2G/3G Access via S4/S8
or Gp interfaces

SMS over SGs Roaming Architecture

Circuit Switched Fallback (CSFB)
Roaming Architecture

GRX Network
 GRX: GRPS Roaming eXchange
 GRX created to carry GTP-tunnels between
different GSM operators
 GRX interconnects in excess of 300 networks and
has proven highly successful
 GRX specification does not meet requirements of
an all-IP LTE network
 IPX as replacement

GRX Model (GPRS Roaming eXchage)

IPX Network
 IPX: IP Packet eXchange
 IPX is an inter-Service Provider IP backbone
network architecture which connects Mobile
Network Operators (MNOs), Fixed Network
Operators (FNOs) Internet Service Providers (ISPs)
and Application Service Providers (ASPs)
 Core enhancement to GRX are end-to-end QoS
and introduction of IPX Proxy
 IPX is isolated from the public Internet and security
rules are defined to prevent unintended access
to/from

IPX Model (IP eXchange)
End-to-end SLA

GRX and IPX Networks
 GRX becomes one of the Service Community types
in the IPX Network
 Only Service Providers that are GPRS/UMTS/LTE
network operators connect to the GRX
 Other types of Service Providers in the IPX Network
do not connect to the GRX service

GRX and IPX Networks (cont.)

Aicent IPX

ATT Logical Architecture

Impacted Elements

Roaming Architecture with DEA

Syniverse IPX Topology

SPGW/GGSN Connectivity to VPLMN

Overall ATT Mobile Core

ASR5500 Overview

Neo Consumer Architecture

DNS Flow Diagram

High Level Logical View of IXC Zone

High Level Logical Network View

Functions of IXC Zone
 Access to GRX/IPX providers for both inbound and
outbound roaming.
 Access layer for roaming specific platforms such as
DEA and IXC DNS.
 Security between external GRX/IPX providers and
core zone.
• A pair of IXC firewalls will control access into the IXC
zone.
• There will also be intrusion protection systems deployed
in the zone to inspect all DNS traffic.

EPS Bearers
 EPS bearers provide the UE access to PDN
services and associated applications
 Default Bearer is established during initial attach
and maintained throughout the lifetime of the
connection (always-on IP connectivity)
 Additional Dedicated Bearers can be established
dynamically when UE requests specific services
(e.g. VoLTE)

LTE Bearer Stacking

ESP Bearers Types
 2 types of EPS Bearers
 Guaranteed Bit Rate (GBR)
Associated ARP and QCI
Allocates resources at admission control
May have separate Maximum Bit Rate (MBR)
 Non-Guaranteed Bit Rate (non-GBR)
Associated ARP and QCI
No resource reservation
May have a Maximum Bit Rate (MBR)

EPS Bearer Types (cont.)
 GBR bearers are established on demand
 Inactivity timers used to free up resources
 Non-GBR bearers can remain established for long
periods (always connected)

QoS Performance Measures
 Throughput: Bit rate, i.e. speed
 Delay: Specified by the packet delay budget. LTE
defines nine categories for delay, with 50 ms being
tightest and 300 ms being the slackest. The latter
value is used for delay tolerant applications
 Packet Loss: Defined as the Packet Error Loss
Rate, and is similar to the packet delay budget in
having nine categories with 10−6 being best and
10−2 being the worst
 Priority: Specified by the Allocation/Retention
Priority (APR) parameter

Service Level QoS Parameters
 Applied per SDF (Service Data Flow) or per SDF
aggregate
 Parameters are:
 QCI: QoS Class Identifier
 ARP: Allocation and Retention Priority
 GBR: Guaranteed Bit Rate
 MBR: Maximum Bit Rate
 AMBR: Aggregate Maximum Bit Rate

QCI and ARP
 QoS Class Identifier (QCI)
To control packet forwarding treatment
 Allocation and Retention Priority (ARP)
To decide if bearer establishment can be accepted or
rejected in case resource limitations exist

QoS Class Identifier
 QCI: QoS Class Identifier
 Used as a reference to a specific packet forwarding
behavior (e.g. packet loss rate,packet delay budget)
to be provided to a service data flow (SDF)
 May be implemented in the access network by the
QCI referencing node specific parameters that
control packet forwarding treatment (e.g.
scheduling weights, admission thresholds, queue
management thresholds, link layer protocol
configuration, etc.), that have been pre-configured
by the operator at a specific node(s) (e.g. eNodeB).

Standardized QCI Values

Allocation/Retention Priority (ARP)
 ARP encoding:
 PCI: Pre-emption Capability
 PL: Priority Level
 PVI: Pre-emption Vulnerability
Bits
Octets 8 7 6 5 4 3 2 1
1 Type = 155 (decimal)
2 to 3 Length = n
4 Spare Instance
5 Spare PCI PL Spare PVI
6 to (n+4) These octet(s) is/are present only if explicitly specified

Priority Level
 PL: Priority Level
 Used for deciding whether a bearer establishment
or modification request can be accepted or needs
to be rejected in case of resource limitations
 Typically used for admission control of GBR traffic
 Also used to decide which existing bearers to pre-
empt during resource limitations
 Values 1 to 15 with 1 as the highest priority level

Pre-emption Vulnerability
 PVI: Pre-emption Vulnerability
 1-bit value: 0 or 1
 Indicates whether a service data flow can lose
resources assigned to it in order to admit a service
data flow with a higher priority level
 Enabled: 0
 Disabled: 1
 Default EPS-Bearer has PVI enabled

Pre-emption Capability
 PCI: Pre-emption Capability
 1-bit value: 0 or 1
 Indicates whether a service data flow can get
resources that were already assigned to another
service data flow with a lower priority level
 Enabled: 0
 Disabled: 1
 Default EPS-Bearer has PCI disabled

Dedicated EPS Bearer Rates
 GBR (Guaranteed Bit Rate): Network resources
allocated based on GBR are fixed and do not
change after bearer establishment or modification.
This is hence a guaranteed service data flow.
 MBR (Maximum Bit Rate): This parameter limits the
bit rate that can be expected to be provided to GBR
bearer, and is enforced by network shaper to
restrict the traffic to its maximum bit rate
agreement.

Default EPS Bearer Rates
 AMBR (Aggregate Maximum Bit Rate): This
parameter is used for non-GBR flows, and has two
types, APN-AMBR and UE-AMBR
 APN-AMBR (Access Point Name AMBR): The
APN-AMBR parameter refers to the maximum bit
rate that can be consumed by all non-GBR bearers
and all PDN connections of a specific APN. This
parameter is enforced in both the downlink and the
uplink.
 UE-AMBR (User Equipment AMBR): refers to the
maximum bit rate allowed for all non-GBR bearer
aggregates for the respective UE. The parameter is
enforced in both the downlink and the uplink.

Uplink/Downlink
 GBR and MBR are defined per bearer while the
AMBR parameters are defined per a group of
bearers
 All throughput parameters (GBR, MBR, APN-AMBR
and UE-AMBR) have two components, one for
downlink and another for uplink.
 Uplink and downlink are usually set to different
values (higher downlink)

Default Bearer Setup
HSS sends APN-
AMBR, ARP and
QCI to MME
HSS sends APN-
AMBR, ARP and
QCI to MME
MME stores
receicev QoS
values in UE
context
MME stores
receicev QoS
values in UE
context
APN-AMBR/QCI/ARP
sent in CSR
APN-AMBR/QCI/ARP
sent in CSR
APN-
AMBR/QCI/ARP
forwarded to PCRF
APN-
AMBR/QCI/ARP
forwarded to PCRF
PCRF modifies
QoS values if
needed and
responds back to
PGW with new
values
PCRF modifies
QoS values if
needed and
responds back to
PGW with new
values
PGW forwards
new values in
response
PGW forwards
new values in
response

ATT QoS Settings for Default EPS Bearer
 APN-AMBR based on SSTI (Subscribed Speed Tier
Indicator) from MIND
 QCI set to 8
 ARP: Priority 10, PCI and PVI enabled
Speed Tier
Indicator
APN-AMBR DL APN-AMBR UL
Low 3.072Mbps (LTE/3G) 3.072Mbps (LTE/3G)
Medium 6.144Mpbs(LTE/3G) 6.144Mpbs(LTE) – 5.696Mbps
(3G)
High 70Mbps(LTE) – 21Mbps(3G) 25Mbps(LTE) – 5.696Mbps (3G)

PCRF behavior in ATT
 For POST subscribers (grandfathered unlimited)
PCRF mirrors back QoS values received from PGW
 For MRC (Monthly Recurring Charge– new
subscribers or ungrandfathered) and SBP (Session
Based Pricing) based on the SSTI of the subscriber
APN-AMBR is enforced
 For MRC and SBP subscribers threshold triggers
are set in the PGW
 For MRC if the threshold is reached (e.g.
3GB/month) speed is throttled
 For SBP the session is blocked

QoS while roaming
 QoS values for on-net subscribers might not be
supported on visited PLMN
 QCI value restrictions might be in place in visited
PLMN (e.g. ATT currently does not allow QCI=7)
 Speed restrictions might be in place in visited
PLMN
 Initial HSS provided values might not be mapped as
desired in visited MME
 PCRF assigned QoS values might mot be
acceptable in visited PLMN

PCRF Roaming Feature
 Introduced to address potential QoS issues for
roaming subscribers
 Addition of 2 new tables in PCRF decision core:
 Location Mapping Table: Allows PCRF to
differentiate QoS assignments based on PLMN ID
(MCC/MNC) and APN
 QoS Mapping Table: Once PLMNID/APN
determined, allows granular QoS assignments
based on RAT type, Billing Plan and Tracking or
Routing Areas

Location Mapping Decision Table
 LocMapping Table maps the APN and PLMNID to a
ROAMING-GROUP
 ROAMING-GROUP used as Input to QoS Mapping
Table
LOCMapping Table
Input Input Output
apn plmnid ROAMING_GROUP
PHONE 302720 1
BROADBAND 302720 1
any any 0

QoS Mapping Decision Table
 QOSMapping table maps roaming_group, RAT
type, RAI/TAI, billing plan and SSTI attributes to
QoS_Ref, roaming_zone and domestic
 If QoS_Ref is not defined (operator error) then subscriber will be defaulted to POST and
QoS values will be mirrored back to PCEF
 Catch all entry for Roaming_Group=1 is to cover CCR-Update cases
QoSMapping Table
Input Input Input Input Input Input Input Input Output Output Output
ROAMING_GROUP rat_type RAI_LAC RAI_RAC TAI_TAC_HB TAI_TAC_LB billing_plan ssti QOS_REF
ROAMING_ZON
E domestic
1 EUTRAN ANY ANY ANY ANY MRC H 1 Off-Net No
1 EUTRAN ANY ANY ANY ANY SBP H 2 Off-Net No
1 ANY ANY ANY ANY ANY ANY ANY mirror
ANY ANY ANY ANY ANY ANY ANY ANY 0

QoS Profiles Table
 Output from the QoS Mapping Table is QoS Ref
 Assigns a specific QoS to subscriber
 AMBR values should be consistent with GTP Coding (TS29.274 and 29.060); otherwise,
PGW will choose the largest value that conforms with GTP code but lower than what's
provisioned
QoSProfiles Table
QoSRef APNAMBR-UL APNAMBR-DL QoS Class PCI PL (Priority
Level)
PVI
1 100kbps 100kbps Interactive-4 Disabled 10 Disabled
2 1500Kbps 3500Kpbs Interactive-4 Disabled 10 Disabled
3 10000kpbs 40000kbps Interactive-4 Disabled 10 Disabled

QoS Class to QCI mapping
QOS-Class to QCI mapping
QoS Class QCI
Conversational-1 1
Conversational-2 2
Streaming-1 3
Streaming-2 4
Interactive-1 5
Interactive-2 6
Interactive-3 7
Interactive-4 8
Background 9

RMS Table
 Roaming Management Service Table
 Maintained by ATT
 Downloaded nightly to PCRF
 Contains all known MCC/MNC and SGSN IP
addresses from ATT and foreign PLMNs
 Output is Roaming Zone and Domestic indicator

Decision Logic
Credit Control Request (MCC/MNC,
SGSN-IP-Address, APN) received by
PCRF from PCEF (PGW)
is
MCC/MNC
defined in
RMS table?
No
Yes
Use MCC/MNC and Roaming Zone values from RMS table
is SGSN_IP
address
defined in
RMS table?
Exit and execute the
default processing
(Roaming zone
=ON_NET, and default
QoS value configured
based on Speed Tier
and RAT type)
Exit and execute the
default processing
(Roaming zone
=ON_NET, and default
based on Speed Tier
and RAT type)
No
Yes

Decision Logic (cont.)
is
ROAMING
GROUP = 0?
Select first ROAMING_GROUP to match
MCC/MNC and APN the Location Mapping Table
Yes
Exit and execute
default processing
(Roaming zone =From
RMS table, and default
based on Speed Tier
and RAT type).
Exit and execute
default processing
(Roaming zone =From
based on Speed Tier
and RAT type).
No
From the Qos Mapping Table select the first entry
that matches Roaming Group, RAT, TAI or RAI,
Billing Plan, SSTI

Decision Logic (cont.)
is QoS_Ref
equal to
“mirror”?
Yes
Exit and mirror back
received QoS values
Exit and mirror back
received QoS values
No
is QoS_Ref
equal to 0?
Yes
Exit and execute
default processing
(Roaming zone =From
based on Speed Tier
and RAT Type)
Exit and execute
default processing
(Roaming zone =From
based on Speed Tier
and RAT Type)
No
• From the QoS Profiles Table (QoSProfiles)
using the QoSRef as key select QoS values
• PCRF replies with CCA-I with the selected
QoS values, either AMBR or
AMBR/QCI/ARP
• From the QoS Profiles Table (QoSProfiles)
using the QoSRef as key select QoS values
• PCRF replies with CCA-I with the selected
QoS values, either AMBR or
AMBR/QCI/ARP

Implementation
 Initial creation of Location Mapping Table and QoS
Mapping Table
 Done as part of the Implementation Guide
 Following slides will cover the addition of a visited
PLMN for customized QoS assignment to roaming
ATT subscribers

PCRF Log in
 Log in to PCRF, click Cisco logo
 Select Decision Tables

Decision Tables

Location Mapping Table
 Select Location Mapping Table
 Use green down arrow key to add a row and green minus sign to
remove a row under Actions
 Enter new PLMN_ID, APN and ROAMING_GROUP
 At a minimum, LOCMapping table should have the catch-all entry
(*ANY*,*ANY*,0)
Add
Remove

Import table from CSV file
 In place of manual entry, a CSV file is imported

Select CSV file to import

QoS Mapping Table
 Select QoS Mapping Table
 Use green down arrow key to add a row and green minus sign
to remove a row under Actions
 At a minimum, QOSMapping table should have the catch-all
entry
Add
Remove

Import table from CSV file
 In place of manual entry, a CSV file is imported

Select CSV file to import

QoS Defintion
 Two types of QoS definitions
 APN Aggregate: To set only APN-AMBR DL/UL
 Extended Default EPS Bearer: To set APN-AMBR
DL/UL, QCI and ARP
 QoS Definitions are named and an appropriate
naming scheme is required, e.g.:
AGG_LOR_01
AGG_LOR_EXT_01

APN Aggregate Definition
 Log in to PCRF and select PCRF
 Go to Configuration->QOS -> QOS Information
 Click “+” to add new QOS. Select APN Aggregate
for QOS Level
 Populate the necessary fields.

APN Aggregate Definition (cont.)

Extended Default EPS Bearer
 Log in to PCRF and select PCRF
 Go to Configuration->QOS -> QOS Information
 Click “+” to add new QOS. Select Extended Default
EPS Bearer for QoS Level
 Populate the necessary fields.

Extended Default EPS Bearer

Import CSV files

Lab Session

Q&A

Thank You

Lte outbound roaming_session

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