Diameter is the next generation Authentication, Authorization and Accounting (AAA) protocol that consists of a base specification and applications. It allows for roaming between networks by authenticating users through their home network and granting access on remote networks. Several organizations are working on Diameter specifications and applications to support different access technologies and services. Further work is still needed to complete specifications for Mobile IP, SIP, and other network applications.

1. Diameter and Diameter Roaming
John Loughney
Research Manager
Nokia Research Center
john.loughney@nokia.com
1 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

2. AAA & Diameter
• Next generation Authentication, Authorization & Accounting
protocol
• Consists of base specification and applications
• MIP
• Network Access Server (Dial-up / PPP / SLIP environment)
• SIP Services
• Accounting Extensions
2 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

3. Standard RADIUS Model
3 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

4. Diameter Roaming
4 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

5. How It Works
• The user requests service from the remote ISP, which in tern
requests the user’s credentials.
• The user submits ID, password and address of his home-
agent. The remote server performs mutual authentication with
the home-agend and forwards the user’s credentials.
• The home-agent accepts the user’s credentials and then tells
the remove ISP to grant access to the user.
• Subsequently, the two ISPs update their call accounting
records.
5 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

6. AAA Elements
• Diameter Node
• A host that implements the Diameter protocol, and acts either as a
Client, Agent or Server.
• Broker
• A business term used in AAA infrastructures. A broker is either a relay,
proxy or redirect agent, and operated by roaming consortiums.
• Diameter Agent
• A host that provides either relay, proxy, redirect or translation services.
• Diameter Client
• A device at the edge of the network that performs access control. An
example of a Diameter client is a Network Access Server (NAS) or a
Foreign Agent (FA).
• Diameter Peer
• Node to which a given Diameter Node has a direct transport connection.
• Diameter Server
• A server that handles authentication, authorization and accounting
requests for a particular realm.
6 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

7. Diameter Connections and Sessions
Server relay Server
Peer connection A Peer connection B
User session X
7 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

8. Translation of RADIUS to Diameter
RADIUS Req Diameter Req
Translation Home
NAS
RADIUS Ans Agent Diameter Req Server
8 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

9. Diameter Proxy Example
local service home service
provider provider
Primary Primary
Proxy Home
Server Server
Network
Access
Server
Backup Backup
Proxy Home
Server Server
9 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

10. Diameter Extensibility
• Diameter tries to preserve Radius -like flexibility
• Diameter base commands and AVPs defined in the base spec
• Diameter extension can define new commands and AVPs.
• Examples are:
• NASREQ
• MOBILE-IP
• 3GPP Credit Control
• 3GPP Multimedia Application
• New AVPs can be added
10 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

11. AAA-SIP in 3GPP Rel. 5
Diameter
SLF HSS AS
Sh
Diameter ISC
Dx Cx Cx
Diameter
Gm Mr
Mw Mw
UE P- I- S- MRFC
CSCF CSCF CSCF
Megaco
Compression Mi
COPS for
Go SIP MRFP
Policy Control
GGSN
Mj
BGCF MGCF SGW
SIP SIP-ISUP
Megaco Mc
Visited Home
Domain Domain
MGW
11 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

12. Work to Do
• Diameter Base Specification just submitted.
• Diameter Mobile IPv4 Application nearly ready (needed by
3GPP2).
• Diameter NASREQ Application nearly ready.
• CMS Security Application, needed for e2e security
• AAA Key Distribution
• SIP-AAA Requirements
• Diameter Mobile IPv6 Application
• Diameter Multimedia Application (3GPP rel. 6)
• Diameter Credit Control Application (3GPP rel. 6)
12 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

13. Summary
• Integrating different access technologies (3G, WLAN, DSL,
Dial-up):
• increases the potential for increasing subscribers.
• increases accesses to services.
• Integrating/harmonizing signaling:
• harmonizes network infrastructure.
• simplifies network management.
• simplifies charging/billing.
• simplifies the user experience.
13 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney

14. More Info
• http://www.diameter.org/
• I will be heading an NRC program
• Access Independent AAA Infrastructure
14 © NOKIA diam-roam.PPT/ 18 December 2002 / John A. Loughney