Diameter Tutorial - IETF67 IETF67 – Diameter Tutorial Diameter Base Protocol Details Victor Fajardo and Yoshihiro Ohba Toshiba America Research Inc. Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Tutorial Outline Diameter – Basic Functionality Message Format Protocol Details Connection Management Routing Session Management Creating new applications Improvements over RADIUS RADIUS to Diameter Transition Support Recent Topics Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Diameter - Basic Functionality Diameter Client Node at somerealm.com Diameter Server Node at otherrealm.com Diameter Client Application Diameter Server Application Session Management Session Management Routing Management Routing Management Connection Management Connection Management Base Protocol Base Protocol Diameter Tutorial - IETF67

Diameter - Basic Functionality Base Protocol Connectivity: Peering and Routing Application support: Application session management Applications Purpose specific: NASREQ, MIPv4, SIP etc. Identified by application Id Every application MUST have an IANA-assigned application identifier Used also for diameter message routing Diameter Tutorial - IETF67

Diameter - Message Format Diameter Header AVP AVP AVP AVP Header AVP Data Diameter Header = Version, Length, Flags, Code, AppId, H2H Id, E2E Id Code, Flag, Length, Vendor-Id (Opt) AVP Header = Each message must be defined using an ABNF grammar Pre-defined AVP data types (Integer32, Float, OctetString etc.) Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Diameter ABNF Example <CER> ::= < Diameter Header: 257, REQ > { Origin-Host } /* Required AVP, Occurrence: 1 */ { Origin-Realm } 1* { Host-IP-Address } /* Required AVP, Occurrence: 1+ */ { Vendor-Id } { Product-Name } [ Origin-State-Id ] /* Optional AVP, Occurrence: 0 or 1 */ * [ Supported-Vendor-Id ] /* Optional AVP, Occurrence: 0+ */ * [ Auth-Application-Id ] * [ Inband-Security-Id ] * [ Acct-Application-Id ] * [ Vendor-Specific-Application-Id ] [ Firmware-Revision ] * [ AVP ] Note: /* */ is not part of ABNF Diameter Tutorial - IETF67

Connection Management Peer Discovery Transport Capabilities negotiation Peer liveness and disconnection Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Peer Discovery Peer discovery mechanisms (in order of preference) Static configuration: mandatory SLPv2 and DNS: optional DNS mechanisms to use (in order of execution) NAPTR Address of record Authorization of discovered peer is mandatory Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Transport Protocols Certain nodes MUST support at least SCTP or TCP (i.e. Diameter Client) Others MUST support SCTP and TCP (i.e. Diameter Servers and Agents) Security TLS and IPSec Selection Process (in order of execution) IPSec, SCTP, TCP, TLS SCTP or TCP is always attempted prior to capabilities exchange TLS tried after capability negotiation IPSec and TLS maybe used exclusively Diameter Tutorial - IETF67

Capabilities Negotiation Capabilities Exchange Use of Capabilities-Exchange (CER/CEA) messages Message exchange advertises: Peer Identity Security schemes – Indicates the use of TLS SCTP host addresses if used CER/CEA may or may not be protected Peer Table Creation Lists all peers that passes capabilities negotiation Indicates the connection status of each peers Also used for message routing Diameter Tutorial - IETF67

Peer Liveness and Disconnection Liveness Test Use of Device-Watchdog exchange (DWR/DWA) Aid in Failover performance: pro-active detection of failure Disconnection Use of Disconnect-Peer exchange (DPR/DPA) Provides hints for future reconnection attempts Routing table updates Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Routing Types of Diameter Nodes Request Routing Realm Routing Table Answer Routing Loop Detection Failover-Failback Procedure Duplicate Detection Diameter Tutorial - IETF67

Types of Diameter Nodes Diameter Clients and Severs Request and Answer Originators Where application normally reside Advertises supported applications only Diameter Agents Request and Answer forwarders Adds routing information to the message Relay Agents Provides basic message forwarding Does not inspect content of the message other than Destination-Host and/or Realm and AppIds Advertises support all applications Diameter Tutorial - IETF67

Types of Diameter Nodes Proxy Agents Inspects and possibly modifies contents of the request or answer it is forwarding. Useful in scenarios such policy enforcement, admission control, provisioning etc Can maintain session state Examples: Translation agents, RADIUS<->DIAMETER Re-Direct Agents Does not forward messages but notifies the previous hop of the new next-hop to use Advertises support all applications Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Diameter Agent Overview Redirect Agent 2. Request 3. Redirect Notification 1. Request 4. Request Client Relay/Proxy Agent Server 5. Answer 6. Answer realmB.com realmA.com Request/Answer Path: Normal Relay or Proxy: 1, 4, 5, 6 Re-directed Agent: 1, 2, 3, 4, 5, 6 Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Request Routing Information used for routing: Application-Id: present is in the header Destination-Host OR Destination-Realm AVP Routing rules: If local identity == Destination-Host AVP then process locally, otherwise If peer identity == Destination-Host AVP then send that peer, otherwise Lookup realm table with Destination-Realm and AppId If found send to the designated next-hop Otherwise, send an UNABLE_TO_DELIVER answer Use of Request Queue Successfully forwarded request are queued Diameter Tutorial - IETF67

Request Routing (Cont’d) Realm Routing Table List of realm routing entries Realm routing entry looks like: Realm (*), AppId (**), Action, Next-hop Peer, isStatic, ExpireTime Realm: Primary key, matched with Destination-Realm Avp AppId: Secondary key, matched with AppId in message header Action: For each matching entry, possible actions are: LOCAL, RELAY, PROXY, REDIRECT isStatic: Indication of static or dynamic route ExpireTime: Time before dynamic route are no longer valid Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Routing Overview SomeOtherRealm.com 1. Request (EAP, Server.RealmB.com) 2. Request (EAP, Server.RealmB.com) Diameter Client Relay/Proxy Agent Diameter Server Request Queue Request Queue 4. Answer 3. Answer Server.RealmB.com Client.RealmA.com Relay.RealmB.com Example Realm Routing Table for Relay/Proxy Agent: RealmB.com AppId=EAP, Action=PROXY, Next-Hop=Server.RealmB.com, isStatic=TRUE AppId=xxx, Action=RELAY, Next-Hop=Server.RealmB.com, isStatic=TRUE RealmA.com AppId=xxx, Action=RELAY, Next-Hop=Client.RealmA.com, isStatic=TRUE SomeOtherRealm.com AppId=EAP, Action=REDIRECT, Next-Hop=Server.RealmB.com, isStatic=FALSE, ExpireTime=3600 Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Answer Routing Information used for routing Hop-by-Hop Id is used instead of Destination-Host or Destination-Realm AVP Hop-by-Hop Id is unique within each hop Answer routing path is the reverse of the request path Routing Rules: For answer originators: Use the same Hop-by-Hop Id found in the request For answer forwarders: Lookup Hop-by-Hop Id in request queue If found, forward answer to appropriate peer and remove request from the queue Otherwise, discard Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Loop Detection Recording the Routing Path Forwarding agents add Route-Record AVPs Detection Local host identity must not be present in the Route-Record AVP Send LOOP_DETECTED answer Diameter Tutorial - IETF67

Failover-Failback Procedure Failover: Attempt to re-route pending request to an alternate peer in case of transport failure ‘T’ bit is set for re-routed requests Failback: Switch back to the original next hop when connection is re-established Relay 3. Request T-bit set Request Queue 4. Answer 2. Request T-bit set Server 5. Answer 1. Request 2. Request Client Relay Request Queue Request Queue 3. Answer 4. Answer Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Duplicate Detection Duplicates can occur Due to Failover Nodes re-sending un-answered requests: Due to reboot Detection End-to-End Id is unique for a node Re-sent request must have T-flag set Therefore, use T-flag as a hint for possible duplication, then Use End-to-End Id and Origin-Host AVP to detect duplication Duplicate request SHOULD cause the same answer to be sent Other Considerations Use of Session-Id for duplicate detection in accounting records Time needed to wait for duplicate messages Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Session Management Diameter Sessions - definitions Session types and statefulness Authentication and Authorization Sessions Accounting Sessions Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Diameter Sessions – definitions What is a session? A session is a related progression of events devoted to a particular activity Applications provide guidelines as to when a session begins and ends Sessions are identified by Session-Id Globally and eternally unique <DiameterIdentity>;<high 32 bits>;<low 32 bits>[;<optional value>] DiameterIdentity: Senders identity in FQDN High and Low 32 bits: Decimal representation of a 64-bit value, monotonically increased Optional value: Implementation specific, i.e. MAC address, timestamp etc Diameter Tutorial - IETF67

Session types and statefulness Two types of sessions by usage Authorization session is used for authentication and/or authorization Accounting session is used for accounting A session can be stateful or stateless Depending on whether the application requires the session to be maintained for a certain duration Stateful sessions normally spans multiple message exchanges Diameter Tutorial - IETF67

Authentication and Authorization Sessions Auth-Session-State indicates statefulness For stateful session Session teardown uses Base Protocol messages ASR/ASA and STR/STA Support for Server-Initiated Re-Auth Uses Base Protocol message RAR/RAA Authorization Session State Machines: CLIENT/STATELESS CLIENT/STATEFUL SERVER/STATELESS SERVER/STATEFUL Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 Accounting Sessions Uses Base Protocol messages ACR/ACA Accounting Session State Machines: CLIENT SERVER/STATELESS SERVER/STATEFUL Diameter Tutorial - IETF67

Accounting-related AVPs Accounting-Record-Type AVP indicates type of accounting record: Acct-Interim-Interval AVP specifies how and when to generate accounting records Accounting-Record-Number AVP identifies an accounting record Acct-Session-Id AVP is used for RADIUS/Diameter translation Acct-Multi-Session-Id AVP co-relates multiple accounting sessions Acct-Sub-Session-Id sub-divides an accounting session Accounting-Realtime-Required AVP specifies realtime accounting behavior Diameter Tutorial - IETF67

Creating a new application Criteria: “New application is unable to fit within an existing application without requiring major changes to the specification” Example major changes: Adding new “mandatory-to-support” AVPs A command requires different round trips than what is currently in the specification Support for a new authentication method with new AVPs As a last resort Advocates reuse of existing applications and AVPs Diameter Tutorial - IETF67

Improvements over Basic RADIUS Features inherently offered by diameter Reliable and secure transport Failover Agent support Server-initiated messages Capabilities negotiation Peer discovery and configuration RADIUS Extensions developed in RADEXT WG also provides most of these functionality, such as RFC3576 Diameter Tutorial - IETF67

Interoperability with RADIUS Diameter is upwards compatible with RADIUS, so Messages and AVPs AVP codes 1-255 is reused from RADIUS Command codes 0-255 is reused from RADIUS Diameter NASREQ (RFC4005) maps RADIUS messages to/from Diameter AA-Request and AA-Answer message Use of RADIUS<->Diameter Translation Agents Diameter Tutorial - IETF67

Interoperability with RADIUS (Cont’d) Translations issues Diameter messages can be larger than maximum RADIUS packet Ongoing work Mapping of new RADIUS extension types to Diameter Diameter Tutorial - IETF67

Recent topics under discussion Usage of Nas-Port-Type and Service-Type vs. defining a new Application Id Use of zero(0) AppId for all base protocol messages Diameter Tutorial - IETF67

Diameter Tutorial - IETF67 End of Tutorial Thank You Diameter Tutorial - IETF67