6831 Intro to Diameter

8/9/2019 6831 Intro to Diameter

1/17


2/17

www.pt.com

Signaling has been an integral part of telecommunications from the beginning.

It is necessary for the establishment and control of a

telecommunications circuit and the management of the network.

2

Evolution of Signaling

As telecommunications networks have advanced,so have the signaling procedures.


3/17

www.pt.com

Evolution of Signaling

3

Channel Associated

Signaling

Common Channel

Signaling

Signaling over IPNGN

Signaling over IP

4G

MF

R1

R2

SS6

SS7

ISUP

SCCP

TCAP

MAP

Circuit Related

Non-Circuit Related

SIGTRAN

SIP

ENUM

M2UA

M3UASUA

M2PA

DIAMETER

SIPPolicy

Charging

Number Portability

Mobility

Supplementary

Services

Intelligent

Network

WATS

Call Setup


4/17

www.pt.com

Within the 3GPP defined

architecture, the handling of the

control signaling is separated

from the user data traffic.

Allow independent scaling of

control and user plane

functions

Control data signaling tends to

scale with the number of users

Data volumes may scale moredependent on new services

and applications

4

Signaling in 4G


5/17

www.pt.com

Diameter is an IETF defined protocol originally designed

for Authentication, Authorization and Accounting (AAA)

as an improvement over RADIUS supporting:

– Improved failure handling – More reliable message delivery

– Bigger information elements

– Improved security

– Extensibility

– More flexible discovery of other nodes

5

Diameter in EPC / IMS

3GPP makes use of two signaling protocols:

– Session Initiation Protocol (SIP) used within the IMS for

setting up sessions.

– Diameter used in both EPC and IMS for transactional

events (requesting information).


6/17

www.pt.com

Relay Agent

– Used to forward a message to the destination, depending on

information within the message.

– Needs to understand base protocol, does not need to understand

the diameter application used.

Proxy Agent

– Similar to relay agent, but can perform additional processing of

the diameter message.

– Needs to understand the service being offered and diameter

application being used.

Redirect Agent

– Performs routing function. Does not forward message towardsthe destination.

– Replies with another message to the node that sent the request

with information allowing the node to send message directly to

the server.

Translation Agent

– Performs translation between diameter and other protocols.

6

IETF Defined Agents

Diameter agents assist in routing of a diameter commandtowards its final destination – the diameter server.


7/17www.pt.com

Diameter Basics

7

ClientRelay

AgentServer

Peer connection Peer connection

Diameter session

Message Structure

Connections


8/17www.pt.com

A diameter agent can act as a centralized routing entity by aggregating requests from

different sources destined to the same destination realm.

Routing typically is performed based on the destination realm as well as the application

identification.

The diameter nodes maintain a list of supported realms and known diameter peers and

their capabilities.

The peer location as well as routing configuration is used when making routing decisions.

8

Routing

HPMN

HSSHSS

vPCRF

VPMN

MMES6A

S6d

S9

GRX/IPX

hPCRF


9/17www.pt.com

RFC 3588 specifies a few general Diameter messages called

commands along with their AVP’s.

Extensions called Applications are created on top of Diameter

base protocol.

9

Extensions to Diameter

Diameter Base Protocol

NAS

Application

(IETF)

Credit Control

Application

(IETF)

S6a/S6d

Application(3GPP Vendor

Specific)

Gx

Application(3GPP Vendor

Specific)

etc….


10/17www.pt.com

Network congestion becomes one of the biggest issues,

highlighted by the popularity of smartphones and M2M.

10

Increase in Diameter Traffic

(Source: Strategy Analytics& ABI Research)


11/17www.pt.com 11

Increase in Diameter Traffic

It is critical for operators to

have the ability to managethis signaling traffic.

Signaling traffic is outpacing actual

mobile data traffic by 30 to 50 percent

due to:

Quantity of Re-attach Messaging

Always on Applications

Push Services

Battery saving Methodologies


12/17www.pt.com

Users make constant queries as they move among cell sites to push email,

access social networking tools and conduct other repetitive actions.

These always-on applications also rely on keep-alive messages.

A web-based IM user may send a message but then wait a couple of

seconds between messages. To preserve battery life, the smartphone moves

into idle mode. When the user pushes another message seconds later, the

device has to set up a signaling path.

12

Causes of Signaling Increase

There are an increased number of

applications that send only a small

amount of data, but the transmission

frequency of the packets is relatively high.


13/17www.pt.com

Fast Dormancy

– In order to keep UE power consumption low, UE sends Signaling Connection Release

Indication (SCRI) to the RNC simulating a failure in the signaling connection.

Heartbeat for Always-on Application

– Heartbeat packets (keep-alive) between client and server end up being sent during themobile device’s idle state, which in turn, triggers the device to continually switch between

active and idle mode over short period time.

Constant Push Service

– Push messages may be sent while the device is on idle mode, which will trigger

unnecessary signaling traffic, such as paging messages, network connection and release

messages.

Network (Re-)Attachment

– Many mobile devices are designed to aggressively keep connecting to the broadband

network as early as possible to ensure a good user experience.

13

Common Smartphone Behaviors


14/17www.pt.com

Need for Diameter Agents

14

Need to concentrate and simplify

the network connectivity to

improve:

Maintainability/Provisioning

Congestion ManagementRouting /Traffic Management

Need for operators to protect their

networks:

Security Firewalls

Topology Hiding


15/17

www.pt.com

Need for Diameter Agents

15

Need for Cost-Effective

and Flexible Network

Deployment

Scalability

Load Balancing

Session Routing

and Control

Interoperability

Value-Added Services

Roaming Management

Roam Steering

Trustednon-3GPP

NonTrustednon-3GPP

P-GW

MME

Gxc

Gx

S6a

Gxa

S9

V-PCRFGxb

S6d

AAASWx

OCS

OFCS

Gy

Gz

SWa

SWd

S6b

STa

Ro

Sh

P-CSCF

Ro

Cx

CxRf

Rx

IMS

HPMN

VPMN

Non-3GPP

HSS

ASI-CSCF

S-CSCF

S6a

HSS

SGSN

MME

S-GWePDG

3GPP

AAA Proxy

H-

PCRFH-

PCRF


16/17

www.pt.com

Diameter Agent Solutions

16

Value Added

Features

Roaming Management

Steering of Roaming

H-PCRF

P-GW

MME

Gx

S6a

AAA

SWx

OCS

OFCS

Gy

Gz

S6b

Ro

Sh

P-CSCFRo

Cx

CxRf

Rx

ASI-CSCF

S-CSCF

H-PCRF

HSS

OCS

HSS

DRALoad Balancer

SLF

HLR

Translation

DEA

Router


17/17

www.pt.com

For more information visit us at:

www.pt .com

Documents

6831 Intro to Diameter