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8/9/2019 6831 Intro to Diameter
1/17
8/9/2019 6831 Intro to Diameter
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.
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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
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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
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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).
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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.
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Diameter Basics
7
ClientRelay
AgentServer
Peer connection Peer connection
Diameter session
Message Structure
Connections
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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
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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….
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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)
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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
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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.
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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
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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
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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
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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
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For more information visit us at:
www.pt .com