As telecommunications networks have advanced, so have the signaling procedures. This introduction to Diameter gives you an overview of the evolution of signaling.

1. Introduction to Diameter
The Evolution of Signaling
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2. Evolution of Signaling
As telecommunications networks have advanced,
so have the signaling procedures.
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.
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3. Evolution of Signaling
Signaling over IP DIAMETER
4G SIP
Policy
Charging
SIGTRAN M2UA
Signaling over IP SIP
M3UA Number Portability
SUA
NGN ENUM M2PA Mobility
Supplementary
ISUP Services
Common Channel SS6 SCCP
Circuit Related
Intelligent
Signaling SS7 TCAP
MAP
Non-Circuit Related
Network
WATS
MF
Channel Associated Call Setup
R1
Signaling R2
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4. Signaling in 4G
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 more
dependent on new services
and applications
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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).
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
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6. IETF Defined Agents
Diameter agents assist in routing of a diameter command
towards its final destination – the diameter server.
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 towards
the 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.
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7. Diameter Basics
Connections
Relay
Client Server
Agent
Message Structure
Peer connection Peer connection
Diameter session
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8. Routing
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.
S6A HSS
MME HSS
S6d GRX/IPX
S9
vPCRF hPCRF
VPMN HPMN
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9. Extensions to Diameter
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.
NAS Credit Control S6a/S6d Gx
Application Application Application Application etc….
(3GPP Vendor (3GPP Vendor
(IETF) (IETF) Specific) Specific)
Diameter Base Protocol
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10. Increase in Diameter Traffic
Network congestion becomes one of the biggest issues,
highlighted by the popularity of smartphones and M2M.
(Source: Strategy Analytics& ABI Research)
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11. Increase in Diameter 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
It is critical for operators to
have the ability to manage
this signaling traffic.
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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.
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.
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13. Common Smartphone Behaviors
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 the
mobile 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.
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14. Need for Diameter Agents
Need to concentrate and simplify
the network connectivity to
improve:
Maintainability/Provisioning
Congestion Management
Routing /Traffic Management
Need for operators to protect their
networks:
Security Firewalls
Topology Hiding
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15. Need for Diameter Agents
IMS
AS
I-CSCF
Sh
OCS Ro S-CSCF
Need for Cost-Effective
P-CSCF
Gy Cx and Flexible Network
MME OFCS Cx
HSS Rf Deployment
HSS Ro
Rx H-
S6a Gz
PCRFH-
PCRF
Scalability
P-GW SWx Load Balancing
Gx AAA
S6b
HPMN Session Routing
and Control
Gxc Interoperability
S-GW SWd
ePDG
S6a
S9 Value-Added Services
S6d
MME
VPMN V-PCRF
Gxb
Roaming Management
SWa 3GPP
SGSN AAA Proxy
Roam Steering
STa
Gxa
Trusted NonTrusted
Non-3GPP non-3GPP non-3GPP
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16. Diameter Agent Solutions
Load Balancer Router DRA
OCS H-PCRF
OCS MME H-PCRF
AS
Gy S6a I-CSCF
Sh
Ro S-CSCF P-CSCF
P-GW
Cx
OFCS
SLF Cx
Rf
Translation
Ro
Gx Gz
Rx
HSS HLR
HSS
S6b
AAA
SWx
DEA
Value Added
Features
Roaming Management
Steering of Roaming
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