diameter_agent_tekelecwp2684.pdf

7/30/2019 Diameter_Agent_TekelecWP2684.pdf

1/12

ImprovIng

performance of

3g, ImS, and LTe

neTworkS wIThThe dIameTer agenT

WHITE PAPER

TabLe of conTenTS

Introduction 2

Creating a Signaling Layer in IP Networks 3

USE CASE 1: Centralized Routing 4

USE CASE 2: LTE Roaming 6

USE CASE 3: HSS Address Resolution 7

USE CASE 4: LTE-to -2G/3G Roaming 7

USE CASE 5: PCRF Binding 8

USE CASE 6: Charging Proxy 9

Summary 12

About Tekelec 12

Appendix: Acronyms Used in This Document 11


2/12

2

ImprovIng

performance of

3g, ImS, and LTe

neTworkS wITh The

dIameTer agenT

InTroducTIon

Mobile data trafc is skyrocketing, fueled by the introduction of data-enabled devices -

smartphones, netbooks, e-readers, and tablets - and compelling applications like mobile

video and social networking And, based on current trends, trafc levels will not level off

in the foreseeable future According to Ciscos Visual Networking Index (February 2011),

there will be a 26-fold increase in global mobile data trafc between 2010 and 2015 - a

staggering compound annual growth rate (CAGR) of 92 percent Operators realize that

their 3G networks are not equipped to sustain this high level of trafc growth They

are looking to all-Internet protocol (IP) networks such as IP multimedia subsystem (IMS)

and long term evolution (LTE) to deliver the bandwidth required to support data-hungry

devices and applications

Diameter protocol, which uses stream control transmission protocol (SCTP) or

transmission control part (TCP) for transport, is widely deployed in the all- IP, service-

oriented IMS and LTE architectures Within the control and service planes, the

application-layer protocol plays a central role in authentication, authorization and

accounting (AAA), policy, charging, and mobility management Diameter serves as the

interface between numerous network resources in 3G and 4G networks, including:

gateway GPRS support nodes (GGSNs), HRPD serving gateways (HSGWs), mobility

management entities (MMEs); online charging systems (OCSs); ofine charging

systems (OFCSs); policy and charging rules function (PCRF); and application servers

In the absence of a Diameter signaling core implemented by Diameter agents (DAs),

endpoints require a direct signaling connection to each other, creating a mesh-like

network architecture They must handle all session-related tasks such as routing, trafc

management, redundancy and service implementation Initially, deploying an IMS or LTE

network without a signaling core may be sufcient However, as trafc levels swell, the

lack of a capable signaling infrastructure poses a number of challenges, some of which

are already being seen today in 3G networks These include:

Scalability: Each endpoint must maintain a separate SCTP or TCP association with

all of its Diameter peers as well as the status of each, placing a heavy burden on the

endpoints as the number of nodes grows

Congestion control: Diameter lacks the well dened congestion control mechanisms

found in other protocols such as signaling system 7 (SS7) For example, if a home

subscriber server (HSS) has multiple Diameter front ends, insufcient congestion

control increases the risk of a cascading HSS failure

Network interconnect: A fully meshed network is completely unworkable when

dealing with connections to other networks because there is no central interconnect

point, which also exposes the operators network topology to other operators and

can lead to security breaches

Interoperability testing (IOT): Protocol interworking becomes unmanageable as

the number of multi-vendor devices increases With no separate signaling or session

framework, IOTs must be performed at every existing node when a new node or

software load is placed in service IOT activities require a considerable amount of

operator time and resources, with costs increasing in proportion to the number of

tests that must be performed


3/12

3

ImprovIng

performance of

3g, ImS, and LTe

neTworkS wITh The

dIameTer agenT

Support for both SCTP- and TCP-based implementations: SCTP-based elements

cannot communicate with TCP-based elements unless they are upgraded or all of the

elements support both protocol stacks

Subscriber to HSS mapping: When there are multiple HSSs in the network,

subscribers may be homed on different platforms Therefore, there must be some

function in the network that maps subscriber identities to HSSs With no separate

Diameter signaling infrastructure, that task could be handled by the HSS This

approach wastes HSS and possible MME (or call session control function [CSCF])

processing, adds unnecessary delays, and may even result in the need for more HSSs

than would otherwise be necessary

PCRF binding: When multiple PCRFs are required in the network, there must be

a way to ensure that all messages associated with a users IP connectivity access

network (IP-CAN) sessions are processed by the same PCRF

creaTIng a SIgnaLIng Layer In Ip neTworkS

The Diameter protocol denes a new network node - the Diameter agent (DA) - which

operators can leverage to create a Diameter signaling layer in IP networks The DA

performs essential network tasks that include relay, proxy, redirect, and translation By

consolidating these functions at the DA, operators can relieve endpoints of routing,

trafc management and load balancing tasks and create a single interconnect point

to other networks This approach eliminates the Diameter/SCTP/TCP, a consequence

of having point-to-point signaling connections between each network element The

resulting architecture, which reduces the cost and complexity of the core network,

enables IP networks to grow incrementally to support increasing service and trafc

demands

Benets

Improves signaling performance and scalability by alleviating issues related to the

limited signaling capacity of MMEs, HSSs, CSCFs, and other Diameter endpoints

Simplies network expansion by limiting routing conguration changes for new

endpoints to the DA

Increases reliability by providing geographic redundancy

Provides mediation of Diameter variants to support interoperability between multi-

vendor endpoints

Creates a gateway to other networks to support roaming, security and topology

hiding

Reduces provisioning, maintenance and IOT costs associated with adding new

network nodes

Enables HSS routing exibility with integrated HSS address resolution function

According to Ciscos

Visual Networking

Index (February 2011),

there will be a 26-

fold increase in global

mobile data trafc

between 2010 and

2015 a staggering

compound annual

growth rate (CAGR) of

92 percent


4/12

4

ImprovIng

performance of

3g, ImS, and LTe

neTworkS wITh The

dIameTer agenT

Creates a centralized monitoring and network intelligence data collection point to

isolate problems and track key performance indicators (KPIs)

Provides network-wide PCRF binding to ensure that all messages associated with a

users particular IP-CAN sessions are processed by the same PCRF

This paper explores six use cases that demonstrate the applications and associated

benets of the Diameter agent in IMS and LTE networks:

Centralized Routing

LTE Roaming

HSS Address Resolution

LTE-to-2G/3G Roaming

PCRF Binding

Charging Proxy

USE CASE 1: CEntrAlizEd roUting

Problem

Operator A, a large mobile operator, deployed an LTE network to increase bandwidth,

lower costs and improve performance of data-enabled applications The operator

has experienced signicant growth in its subscriber base and needs to expand its

network with new MMEs and HSS front ends The addition of the new resources

presents a challenge Diameter protocol, using SCTP for transport, interconnects many

of the network elements in the operators evolved packet core (EPC) Each Diameter-

based element must have a direct SCTP association with every element to which it is

connected, creating a logical mesh network As a result, the addition of new resources

requires conguration and routing updates at each and every network element

Solution

With a DA, Operator A can decrease the cost and complexity of its core LTE networkThe DA serves as a Diameter relay, thereby reducing the number of SCTP associations

in the network and ofoading Diameter routing tables and routing-status maintenance

from the end nodes The MMEs connect to a mated pair of DAs, which interface to the

HSS front ends and to other networks When Operator A deploys new MMEs or HSS

front ends, routing updates are required only at the DAs

The MMEs connect to

a mated pair of DAs,

which interface to the

HSS front ends and to

other networks


5/12

5

ImprovIng

performance of

3g, ImS, and LTe

neTworkS wITh The

dIameTer agenT

Figure 1. Centralized Routing (before)

Figure 2. Centralized Routing (after)

IMS Registration

AS Accessto HSS

EPC EquipmentCheck

IMS PCCIP-SM-GW

vS4-SGSN

vSGSN

vPCRFvMME

Gx

Gz

PCRF

P-CSCF

Gr

MME

S13

SPR

AF

SLF

MAP-Diam

IWF

Ro

PGW

ABMF RF

Rc Re

Rf

I/S-CSCF

CxRx

Sh

Gy

Sh

S6a S9S6d

Foreign LTE Domain

Home LTE/IMS Domain

Foreign GPRS Domain

IMS ChargingEPC Charging

EPC MobilityManagement

EIR

Policy

Foreign LTE Domain Foreign GPRS Domain

Home LTE/IMS DomainMME PCRF

P-CSCF I/S-CSCF

Diameter

Agent

vPCRF

SS7

DiameterAgent

PGW

AF

ABMF

IP-SM-GW

vMME

vS4-SGSN

vSGSN

DiameterAgent


6/12

6

ImprovIng

performance of

3g, ImS, and LTe

neTworkS wITh The

dIameTer agenT

Benets:

Reduces the complexity and improves the scalability of the core LTE network

Lowers OPEX by simplifying provisioning and updates

Creates a more exible architecture

USE CASE 2: ltE roAming

Problem

Operator B, has encountered a problem when its LTE subscribers roam into foreign

LTE networks Because the LTE network has no core routing layer, there is no central

interoperability point from which to manage roaming to/from other networks, and the

endpoints must take on all trafc and routing management tasks This set-up not only

burdens the endpoints, but also creates potential security threats Because there is no

network demarcation point, the operator has no way to hide its topology or effectively

secure the network

Solution

By deploying a DA, Operator B can create a single interconnect point to other networks

The DA consolidates all incoming and outgoing network trafc and handles the

management tasks associated with roaming handoffs As the rst point of contact at the

networks edge, the Diameter agent provides a centralized vantage point from which theoperator can defend against potential overloads or attacks

Figure 3. LTE Roaming

Benets

Increases network security and hides network topology

Simplies routing and interconnection to other networks

Because the LTE

network has no core

routing layer, there is nocentral interoperability

point from which to

manage roaming to/

from other networks,

and the endpoints must

take on all trafc and

routing management

tasks

MME MME MME

Operator_2

Operator B

MME

Operator_N

MME

DiameterAgent

DiameterAgent

HSS FE HSS FE HSS FE HSS FE

DiameterAgent

PCRF

PCRF

PCRF


7/12

7

ImprovIng

performance of

3g, ImS, and LTe

neTworkS wITh The

dIameTer agenT

USE CASE 3: HSS AddrESS rESolUtion

Problem

Operator C plans to deploy new HSSs in its LTE network but has encountered an issue

With the addition of new HSSs, the operators subscribers will be homed on different

platforms Operator C must nd a cost-effective solution to provide and maintain the

association of subscriber to HSS

Solution

The DA centralizes routing data and provides the mapping between a subscriber identity

(eg, IMS Public ID, IMSI) and an HSS This exibility enables Operator C to easily move

subscribers from one HSS to another With the DA, subscriber number ranges can be

split over different HSSs and individual subscriber numbers can be assigned to any HSS

Figure 4. HSS Address ResolutionBenets

Simplies HSS provisioning by centralizing routing data

Enables dynamic updates as new HSS are placed in service

Provides for easy support of mergers and acquisitions

USE CASE 4: ltE-to -2g/3g roAming

Problem

Operator D deployed an LTE network and provided its subscribers with multi-mode

handsets Since many of its roaming partners have not deployed LTE, Operator Ds

subscribers are encountering problems when they roam in 2G/3G networks because

of the disparity in protocols used to manage mobility Mobile application part (MAP)

protocol is used in 2G/3G networks as the interface between nodes such as serving

SGSNs and home location registers (HLRs) for mobility management and authentication

In LTE, MAP has been replaced with the Diameter protocol To support seamless roaming

and handoffs between LTE and 2G/3G networks, Operator D needs a function to

interwork the two protocols

DiameterAgent

Subscriber 2

Subscriber 3

Subscriber 1

eNode B

1

3

LTEMME

2

SGW


8/12

8

ImprovIng

performance of

3g, ImS, and LTe

neTworkS wITh The

dIameTer agenT

Solution

The DA, serving as a gateway to other networks, provides the Diameter/MAP

interworking function to enable seamless subscriber roaming Along with message

mapping, the DA provides mapping between SS7 addresses/point codes and Diameter

node IDs This allows Operator D to support seamless roaming and handoff between LTE

and 2G/3G networks

Figure 5. LTE-to-2/3G Roaming Update Location Depiction

Benets

Simplies network migration to LTE

Supports seamless 2G/3G roaming

USE CASE 5: PCrF Binding

Problem

Operator F is planning to deploy multiple PCRFs in its network to improve scalability

Operator F needs a way to balance the assignments of user IP-CAN sessions to PCRFs

and to make sure all messages for a subscriber are handled by the same PCRF These

messages can arrive on different interfaces (for example, Gx and Rx) and may be

identied by different elements such as IMSI and IP address

Solution

The DA, providing the 3GPP Diameter routing agent (DRA) proxy function, supports

static binding or dynamic load sharing across PCRFs when IP-CAN sessions are rst

established The DA ensures that subsequent messages over the Gx, S9, Gxx, or

Rx reference points are sent to the same PCRF Additionally, the DA extends this

functionality across multiple DAs in Operator Fs network, which communicate with

each other to act like a single, logical DRA

The DA ensures that

subsequent messages

over the Gx, S9, Gxx, or

Rx reference points are

sent to the same PCRF

DiameterAgent

MAP

Operator D Roaming Network

Subscriber 1

Diameter

IP SS7vSGSN

Subscriber 1


9/12

9

ImprovIng

performance of

3g, ImS, and LTe

neTworkS wITh The

dIameTer agenT

Figure 6. PCRF Binding

Benets

Enables PCRF scalability

Solves network-wide PCRF binding problem

USE CASE 6: CHArging Proxy

Problem

Operator G has deployed the Rf Diameter interface for ofine charging The charging

trigger function, which resides in a number of network elements in Operator Gs

network, such as GGSNs and signaling gateways (SGs), is directly connected to

ofine charging systems As the network grows, Operator G is nding the mesh-like

architecture created by the direct connections between the elements increasingly difcult

to manage The SGSNs and SGs, as Diameter clients, must support load distribution

and failover for Diameter messages toward the charging servers Operator G must

independently test the same failover models on each client type it adds to the network, a

costly approach that delays time to market

Solution

Acting as an ofine charging proxy, the DA handles message routing between the

charging clients and the OFCF It provides load distribution and failover support between

the clients and servers as well as topology hiding The DA appears as a single charging

server to the GGSNs or SGs and as a single charging trigger to the OFCFs As a central

Diameter mediation point, it enables the interworking of multivendor clients and servers

The SGSNs and SGs,

as Diameter clients,

must support load

distribution and failover

for Diameter messages

toward the charging

servers

To/From Other

Networks

IPX

DiameterEdgeAgent

PCRF

PCRF

P-CSCF

PGW/HSGWGx.Gxx

Rx

Gx.Gxx

Rx

DRA

DiameterAgent

DiameterAgent

DiameterAgent

DiameterAgent

P-CSCF

PGW/HSGW

DRMA

Region1

Region 2

DRA

PCRF

PCRF

P-CSCF

PGW/HSGWGx.Gxx

Rx

Gx.Gxx

Rx

DRA

DiameterAgent

DiameterAgent

P-CSCF

PGW/HSGW

DRMA

Region1

Region 2

DRA


10/12

10

ImprovIng

performance of

3g, ImS, and LTe

neTworkS wITh The

dIameTer agenT

Figure 7. Ofine Charging

Benets

Reduces operation, administration and maintenance costs

Enables efcient OFCF usage

Improves network reliability, scalability and resilience

Summary

Operators are turning to all-IP networks like IMS and LTE to provide the bandwidth

to support swelling data loads However, if those networks are deployed without a

separate Diameter signaling core, a host of challenges related to scalability, security,

mobility management, and routing will arise as trafc loads escalate Providers can

overcome these challenges by leveraging the Diameter agents proxy, redirect, relay and

translation capabilities Consolidating these functions at the DA creates a core Diameter

signaling layer that relieves endpoints of routing, trafc management and load balancing

responsibilities The resulting architecture provides the exibility and scalability to support

even the most data-intensive devices and applications

abouT TekeLec

Tekelec connects people and devices to the mobile Internet Our portfolios unique

layer of network intelligence allows service providers to both manage and monetize the

exponential growth in mobile web, video and applications trafc Tekelec has more than

25 ofces around the world serving customers in more than 100 countries For more

information, visit wwwtekeleccom

Site 1

GGSN SGW CSCF/TAS

ChargingProxy

PGW

Site 2

GGSN SGWCSCF/TAS

ChargingProxy

PGW

Rf


11/12

11

ImprovIng

performance of

3g, ImS, and LTe

neTworkS wITh The

dIameTer agenT

appendIx: acronymS uSed In ThIS documenT

3GPP Third Generation Partnership Project

AAA Authentication, Authorization and Accounting

CAGR Compound Annual Growth Rate

CSCF Call Session Control Function

DA Diameter Agent

DRA Diameter Routing Agent

EPC Evolved Packet Core

GGSN Gateway GPRS Support Nodes

HLR Home Location Register

HSGW HRPD Serving Gateways

HSS Home Subscriber Server

IMS IP Multimedia Subsystem

IOT Interoperability Testing

IP Internet Protocol

IP-CAN IP Connectivity Access Network

KPI Key Performance Indicator

LTE Long Term Evolution

MME Mobility Management Entity

NMS Network Management System

OCS Online Charging System

OFCF Ofine Charging Function

PCRF Policy and Charging Rule Function

QoE Quality of Experience

QoS Quality of Service

SCTP Stream Control Transmission Protocol

SG Signaling Gateway

SLF Subscription Locator Function

SS7 Signaling System 7

TCP Transmission Control Part


12/12

Tekelec has more than 300 customers in more than 100 countries. For information on our

worldwide ofces, visit the Tekelec website at www.tekelec.com/ofces.

This document is for informational purposes only, and Tekelec reserves the right to change any aspect of

the products, features or functionality described in this document without notice Please contact Tekelec

for additional information and updates Solutions and examples are provided for illustration only Actual

implementation of these solutions may vary based on individual needs and circumstances

2012 Tekelec All rights reserved TEKELEC, EAGLE, TekServer, G-Flex, G-Port, and CAMIANT are

registered trademarks of Tekelec

The Tekelec logo, A-Port, EAGLE 5 ISS, V-Flex, ngHLR, Diameter Signaling Router (DSR), BLUESLICE,

and Subscriber Data Server (SDS) are trademarks of Tekelec Other product names used herein are foridentication purposes only and may be trademarks of their respective companies

www.tekelec.com

Tekelec Global Headquarters

+1.919.460.5500

888.628.5527

[email protected]

EMEA +44.1784.437000

APAC +65.6796.2288

CALA +1.919.460.5500

diameter_agent_tekelecwp2684.pdf

Documents