Introduction to Diameter Protocol - Part1

1 Copyright © 2011 Juniper Networks, Inc. www.juniper.net
Introduction to Diameter Protocol
BASIM ALY
Senior Network Engineer
basimaly.wordpress.com eg.linkedin.com/pub/basim-aly/38/774/228/

What’s Diameter
• Diameter is an authentication, authorization, and accounting protocol
• Work within AAA Framework
• Provides an upgrade path for RADIUS
• Dynamic discovery of peers (using DNS SRV and NAPTR)
• Capability negotiation
• Error notification
• RFC 6733

Reliable Transport Depend on TCP to transport the message
More Secure Depend on IPSEC and STCP protocols
WIDER Twice as radius in AVP!
App based-
Extensible
You can extend the core code by building your own application
over the top
Why use DIAMETER over the RADIUS?

One More reason
Once subscriber reached to purchased quota, The diameter client will trigger an
event to inform the server, However in radius-based network you have to wait for
the incoming Accounting-Interim to trigger this action which is considered a
revenue leakage

Protocol Stack
Supported Protocols Standard / Specification Used
Diameter IETF RFC 3588
S6a, S6d, S13 - 3GPP TS 29.272 V10.3.0
Rx - 3GGP TS 29214-b10
Cx/Dx - 3GPP TS 29.228 & TS29.229
Gx - 3GPP TS 29.212 & TS 23.203
Sh - 3GGP TS 29.328 & TS 29.329
Gy/Ro (DCCA)- 3GGP TS 32.225, 3GPP TS
32.299 and IETFRFC 4006
SCTP RFC 4960
TCP RFC793

Diameter Elements
MME (Mobility Management Entity)
HSS (Home Subscriber Server)
EIR (Equipment Identity Register)
CSCF (Call Session Control Function)
PCRF (Policy and Charging Rules Function)
PCEF (Policy and Charging Enforcement Function)
SGSN (Serving GPRS Support Node)
PDN GW (Packet Data Network Gateway)

CCA
We will discuss this scenario later!
Through passing CGI (Cell Global Identifier) and RAI (Routing Area
Identifier) from PCEF (GGSN) to PCRF in Event-Trigger AVP
Support Roaming(Inter-PLMN)!

Diameter Core Protocol
Application1 (Gx) Application2 (SIP)
• Diameter allow you to write a new application as an extension to base
code. these apps not a software app but a new protocols that use diameter
original code
• The Diameter protocol will replace the SS7 and SIGTRAN by
introducing a new Interfaces (Apps!) that will connect to HSS
Diameter Applications

Diameter RADIUS
Transportation Protocol
Connection-Oriented
Protocols (TCP and SCTP)
Connectionless Protocol (UDP)
Security Hop-to-Hop, End-to-End Hop-to-Hop
Agent Support
Relay, Proxy, Redirect,
Translation
Implicit support, which means the
agent behaviors might be
implemented in a RADIUS server
Capabilities Negotiation
Negotiate supported
applications and security
level
Don't support
Peer Discovery
Static configuration and
dynamic lookup
Static configuration
Server Initiated Message
Supported. for example, re-
authentication message,
Session termination
Don't support
Maximum Attribute Data Size 16,777,215 octets 255 octets
Vendor-specific Support
Support both vendor-
specific messages and
attributes
Comparison Between Radius and Diameter

Port 3868
Application Layer
Req/Answer Style
Other Properties

• PCEF
• IP-CAN
• Bearer
• PCC
New Definitions

• An access network that provides Internet Protocol (IP) connectivity.
• The term is usually used in cellular context
1 of 3
IP-CAN(IP Connectivity Access Network)
New Definitions

The IP-CAN domain ends with the GGSN or (P-GW) node and it
created after the PCRF install the rules in PCEF
2 of 3
New Definitions
IP-CAN

• 3GPP-GPRS (0) This value shall be used to indicate that the IP-CAN is
associated with a 3GPP GPRS access that is connected to the GGSN
based on the Gn/Gp interfaces and is further detailed by the RAT-Type
AVP. RAT-Type AVP will include applicable 3GPP values, except
EUTRAN.
• DOCSIS (1) This value shall be used to indicate that the IP-CAN is
associated with a DOCSIS access.
• xDSL (2) This value shall be used to indicate that the IP-CAN is
associated with an xDSL access.
• WiMAX (3) This value shall be used to indicate that the IP-CAN is
associated with a WiMAX access (IEEE 802.16).
3 of 3
IP-CAN Types
New Definitions

• 3GPP2 (4) This value shall be used to indicate that the IP-CAN is
associated with a 3GPP2 access connected to the 3GPP2 packet core
as specified in 3GPP2 X.S0011 [20] and is further detailed by the RAT-
Type AVP. AVP.
• 3GPP-EPS (5) This value shall be used to indicate that the IP-CAN
associated with a 3GPP EPS access and is further detailed by the RAT-
Type AVP.
• Non-3GPP-EPS (6) This value shall be used to indicate that the IP-CAN
associated with an EPC based non-3GPP access and is further detailed
by the RAT-Type
3 of 3
IP-CAN Types
New Definitions

Capacity 1 Delay 1 Bit-Error Rate 1
Capacity 2 Delay 2 Bit-Error Rate 2
Bearer 1
Bearer 2UE
The Bearer is created inside IP-CAN according the service requirement. If you
have VoLTE service that need high bandwidth with low latency, and browsing
service that work on best effort then you need two Bearers for the same IP-
CAN with different QoS
New Definitions
1 of 2
Bearer

Default bearer
Dedicated bearer
for VoIP for example
APN-Aggregate-Max-Bitrate-UL=1M
APN-Aggregate-Max-Bitrate-DL=2M
Max-Requested-Bandwidth-UL=10M
Max-Requested-Bandwidth-DL=10M
Bearer-Identifier=999
Default-EPS-Bearer-QoS AVP
QoS-Information AVP
2 of 2
New Definitions
Bearer AVP

This is Policy and Charging Control. It could be either Dynamic (Rules are
pushed from PCRF to PCEF) or Static (PCRF just Activate or Deactivate the
pre-defined rules in PCEF)
Dynamic Static
1 of 1
New Definitions
PCC

• Each command is either a request or answer is assigned a command
code
• The request or answer is identified via the ’R’ bit in the Command Flags
field of the header.
Command Code

Capabilities-Exchange
Device-Watchdog
Credit Control
Command Code
Most Important Command codes

Capabilities-Exchange
CER CEA
1
• A negotiation message between diameter peers to agree on supported
applications
• Command Code Number : 257
• Diameter peers use it to create peer table
• Message Exchange advertise the following:
• Peer Identity
• Use the secure transport or not
• SCTP Host address
Command Code

Device-Watchdog-Request
DWR DWA
• A keep alive message between the diameter peers to watch the status
and availability
• Command Code Number : 280
Keep Alive, We need You JIM!
2
Command Code

Device-Watchdog-Request
DWR DWA
2
Command Code

R(Request),P (Proxiable), E (Error Response) T(Re-Transmission of
Request)
Here it’s a Request message sent to peer
Command Flags

Multiple Diameter AVPairs can be grouped inside one large AVP
AVPairs

Session-Id1
AVP: Session-Id(263) l=47 f=-M- val=qps.tedata.net;4FD78691;5458;3B9ACA00;0
AVPairs
• The Session Identifier for the Subscriber
• Never Changed as long as the Subscriber session is up
• Consist of the diameter peer name followed by unique number

• Each vendor create application should have a unique vendor ID
Vendor-Id2
AVPairs

• Identify the broadcasted Diameter Origin Peer Name
• Example : Origin-Host : pcef1.tedata.net.eg
Origin-Host3
AVPairs

Origin-Realm4
AVPairs
• Identify the broadcasted Diameter Origin Realm
• Example : Origin-Realm : tedata.net.eg

Destination-Realm5
AVPairs
• Identify the broadcasted Diameter Origin Realm
• Example : Destination-Realm : Sandvine.com

Destination-Host6
AVPairs
• Identify the broadcasted Diameter Destination Realm
• Example : Destination-Host : PTS.sandvine.com

Host-IP-Address7
• The Source IP address that initiate the Diameter message
• Sent in HEX format
• Example : Host-IP-Address: 1.1.1.7
• Use the below website to obtain the hex value from IP Address
http://ncalculators.com/digital-computation/ip-address-hex-
decimal-binary.htm
Padding 0x0001
0x00010A8347AC
AVPairs

Event-Trigger8
Sent from PCEF to PCRF to inform it of specific Event occur
Example Values:
• Event-Trigger: LOSS_OF_BEARER
• Event-Trigger: SGSN_CHANGE
• Event-Trigger: RAI_CHANGE
AVPairs

Uniquely identify the supported application ID (Gx, Gy, Vodafone Gx, E///..etc)
3GPP Gx Application ID =16777238, Old was 16777224.
Check this link http://www.iana.org/assignments/aaa-parameters/aaa-parameters.xhtml
Application ID

Credit Control Application1
• Used to identify the credit control application
• Associated with CC-Request-Type
• INITIAL_REQUEST (CCR-I) or (CCA-I)
• UPDATE_REQUEST (CCR-U) or (CCA-U)
• TERMINATION_REQUEST (CCR-T) or (CCA-T)
Application ID

Auth-Application-Id
The Auth-Application-Id AVP (AVP Code 258) is used in order to advertise
support of the Authentication and Authorization portion of an application. The
Auth-Application-Id MUST also be present in all Authentication and/or
Authorization messages that are defined in a separate Diameter specification
and have an Application ID assigned.
Acct-Application-Id
The Acct-Application-Id AVP (AVP Code 259) is used in order to advertise
support of the Accounting portion of an application The Acct-Application-Id
MUST also be present in all Accounting messages. Exactly one of the Auth-
Application-Id and Acct-Application-Id AVPs MAY be present.
AVPairs

Developed Application
Authentication Portion
of application
Authorization Portion
of application
Accounting Portion of
application
Diameter Core
Auth-Application-Id AVP Acct-Application-Id AVP
109
Application-Id
Vendor-Id
AVPairs Summary

Diameter Agents
RELAY
PROXY
Redirect
Translator
Route message without changing it
Route message and can change it
Don’t route the message but can provide routing info
Translate between Radius and Diameter
What’s the role of your server?

 Build over Diameter Core Protocol
 Provide a framework for real-time charging
 The application specifies methods for:
 Quota management (Reserve, Reauthorize, Abandon)
 Simple Debit/Credit
 Balance checks
 Price inquiries
 Does not specify which type units are bought/used
 CCR/CCA
Credit Control

The purpose of the diameter credit control application is to
provide a framework for real-time charging, primarily meant for
the communication between gateways/control-points and the
back-end account/balance systems (typically an Online
Charging System)
Command Code = 272 Auth-Application-Id=4
Credit Control

Credit-Control-Request (CCR) Command
The Credit-Control-Request message (CCR) is indicated by the command-code
field being set to 272 and the 'R' bit being set in the Command Flags field. It is
used between the Diameter credit-control client and the credit-control server to
request credit authorization for a given service. The Auth-Application-Id MUST
be set to the value 4, indicating the Diameter credit-control application.
Credit Control Request(CCR)

 CCA Command sent from PCRF to PCEF as a
response to CCR
 Provide PCEF with the following info
 PCC rules
 Event Trigger (When to report an event back to PCRF)
 Selected bearer control mode for the IP-CAN session
Credit Control Answer(CCA)

Gx
Policy Enforcement
Gy Gz
CDR sent to OFCSCDR sent to OCS
Credit Control Interfaces

PCEF/DPI
CC-Request-
Type=Initial
Credit Control
Answer
ReAuthorization
Request
ReAuthorization
Answer
Note the request is sent
using the Subscriber Name
and IP address received
from Radius accounting
ThisiscalledIP-
CANsession
1-Subscriber is connected to BNG which will send accounting start to AAA.
2-AAA will proxy accounting to DPI contains the username and IP Address
3-user start to browse internet and send traffic through the DPI
4-DPI will stop the traffic and will send CCR-I with IP address to PCRF. Smth like
query to get the username
5-PCRF will consult the SPR and will return the policies in CCA
Attach to
Network
1

1-PGW send CCR-I with Subscriber-Id (IMSI or MSISDN or etc...) and Framed-
IP (IP address what network give for this device) to PCRF
2-PCRF calculate user tariff and respond policy or bearer settings
Calculate
Tariff in real
time
2

 Interface between PCEF (BNG/DPI/GGSN) and
PCRF
 PCRF send PCC rules to be installed on PCEF
 Upon receive of an Event-Trigger, PCRF can puch a
new PCC rule over Gx for new bearer creation
Gx Interface

OCS
 Used for Online Charging (Pre-Paid)
 Used to take real-time decision on tired services
Gy Interface

OFCS
 Used for Offline Charging (Post-Paid)
 offline charging is a mechanism where charging
information does not affect, in real-time, the service
rendered.
Gz Interface

Credit Control Interfaces Summary

Username Identifier
• Subscriber username sent in Subscription-Id AVP
• Subscription-Id consist of two AVPs
– Subscription-Id Type
• Type of connected subscriber (Mobile, ADSL..etc)
– Subscription-Id value

<Subscription-Id>
<Subscription-Id-Type Value="END_USER_SIP_URI" />
<Subscription-Id-Data Value="sip:+3251001011@tedata.net.eg" />
</Subscription-Id>
<Subscription-Id>
<Subscription-Id-Type Value="END_USER_NAI" />
<Subscription-Id-Data Value=“basim@tedata.net.eg" />
</Subscription-Id>
1
2
For VoLTE
(Mobile
Operator)
For
xDSL/FTTx
ISP
Subscription-Id

Credit Control PCEF Sample Configuration(1/3)
#vi /usr/local/sandvine/etc/diam_peer_config.xml
<diameter-peer>
<peers>
<peer>
<identity>host1.freepcrf.com</identity>
<hostname>1.1.1.90</hostname>
<realm>freepcrf.com</realm>
<port>3868</port>
<bias>2</bias>
<dictionaries>
<dictionary>Rf</dictionary>
</dictionaries>
</peer>
</peers>
IP Address
for PCRF
Supported
App

#vi /usr/local/sandvine/etc/diam_peer_config.xml
<identities>
<local-identity>
<identity>PTS.tedata.net</identity>
<display-name>PTS.tedata.net</display-name>
<realm>tedata.net</realm>
<dictionaries>
<dictionary>Rf</dictionary>
</dictionaries>
<client-config>
<watchdog-timeout>10</watchdog-timeout>
<cea-timeout>5</cea-timeout>
<connection-timeout>1</connection-timeout>
</client-config>
</local-identity>
</identities>s
Identify
PCEF
identity
Supported
App
Watchdog
parameters

• Identify Destination Realm
• Identify the Original Realm
• Identify the IP_CAN_TYPE = ADSL
• Identify the Subscription-id type = NAI
• Identify the Subscription-id value Sandvine
DPI PTS

First thing that you should notice inside the diameter protocol packets is the Command
Code AVP and CC-Request-Type AVP that indicates the type of request whether it’s
INITIATE(CCR-I) or UPDATE or TERMINIATE..etc
Request
- Initial
CC
CCR-I
Credit Control PCAP

• Seagull is a free, Open Source (GPL) multi-
protocol traffic generator test tool.
• powerful traffic generator
• Used for stress testing
• Developed by HP
• Coded using C++
• Simulation tool developed by HP to simulate
different protocols
• SIP
• Diameter
• Radius
• Support Linux (Centos/Debian) and Windows
(Through cygwin
Seagull
http://gull.sourceforge.net/

Download1
http://sourceforge.net/projects/gull/files/seagull/
Seagull

Install Seagull2
#tar zxvf seagull-1.8.2-Linux_RHEL6U1_X86_64.tar.gz
#cd packages/
#wget
ftp://ftp.pbone.net/mirror/ftp5.gwdg.de/pub/opensuse/repositories/ho
me:/csbuild:/DBA/RedHat_RHEL-6/x86_64/dba-openssl-098o-0.9.8o-
2.2.x86_64.rpm
#rpm -ivh dba-openssl-098o-0.9.8o-2.2.x86_64.rpm
#rm dba-openssl-098o-0.9.8o-2.2.x86_64.rpm
#rpm -ivh seagull-core-1.8.2-linux-2.6-intel.rpm
#rpm -ivh seagull-diameter-protocol-1.8.2-linux-2.6-intel.rpm
#rpm -ivh seagull-external-lib-sctp-1.8.2-linux-2.6-intel.rpm
#rpm -ivh seagull-trans-sctp-1.8.2-linux-2.6-intel.rpm
#rpm -ivh seagull-trans-tls-1.8.2-linux-2.6-intel.rpm
#rpm -ivh seagull-radius-protocol-1.8.2-linux-2.6-intel.rpm
Seagull

Define the correct client configuration3
#vim /opt/seagull/diameter/config/conf.client.xml
Define the correct dictionary file to be used for both client and server4
#vim /opt/seagull/diameter/config/base_cc.xml
Define the scenario5
#vim /opt/seagull/diameter/scenario/ccr-cca.client.xml
Seagull

Create Run script to use the files you created before6
#cd /opt/seagull/diameter/run
#vim start_client_gx_ccr_cca.ksh
#!/bin/ksh
export LD_LIBRARY_PATH=/usr/local/bin
seagull -conf /opt/seagull/diameter/config/conf.client.xml -dico
/opt/seagull/diameter/config/base_cc.xml -scen
/opt/seagull/diameter/scenario/ccr-cca.client.xml -log
/opt/seagull/diameter/logs/ccr-cca.client.log -llevel ET
Run the test7
cd /opt/seagull/diameter/run
./start_client_gx_ccr_cca.ksh
Seagull

Configure Client
(PCEF)
 Create Channel (Diam version..)
 Whom to open channel with (PCRF IP)
 Call ch (Rate/timeout/max number..)
 Load external data
 Where to log the events
#vim /opt/seagull/diameter/config/conf.client.xml
Seagull

Configure Dictionary
 Diameter header (CMD, HbH, EtE..)
 Diameter base AVP with their values
 Define diameter commands structure (CER,
CCR, RAR..)
 Here you should define any vendor-spcefic
attributes (next slide)
Seagull

Configure Dictionary
Add new
AVP
Seagull

Configure Scenario
 Configure init section (configure both Send &
Receive tags that negotiate CER)
 Configure traffic section (configure both Send &
Receive tags that send actual traffic)
#vim /opt/seagull/diameter/scenario/ccr-
cca.client.xml
Seagull

Run
 Connecting the dots
 Identify the config location
 Identify the dictionary location
 Identify the scenario
 Identify where to store the log
 Identify the debug level
#vim
/opt/seagull/diameter/run/start_client_cc.ksh
#export LD_LIBRARY_PATH=/usr/local/bin
#seagull -conf ../config/conf.client.xml -dico
../config/base_cc.xml -scen ../scenario/ccr-cca.client.xml -log
../logs/ccr-cca.client.log -llevel ET
If you can’t find seagull command, then copy content of seagull
bin folder the package to /usr/bin directory
You may need to install KSH package from YUM/apt-get
Seagull

Introduction to Diameter Protocol - Part1

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