INTERNET DRAFT Pat R. Calhoun Category: Standards Track Sun Microsystems, Inc. Title: draft-calhoun-diameter-17.txt Allan C. Rubens Date: September 2000 Tut Systems, Inc. Haseeb Akhtar Nortel Networks Erik Guttman Sun Microsystems, Inc. DIAMETER Base Protocol Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at: http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at: http://www.ietf.org/shadow.html. This document is an individual contribution for consideration by the AAA Working Group of the Internet Engineering Task Force. Comments should be submitted to the diameter@diameter.org mailing list. Distribution of this memo is unlimited. Copyright (C) The Internet Society 1999. All Rights Reserved. Calhoun et al. expires March 2001 [Page 1] INTERNET DRAFT September 2000 Abstract The DIAMETER base protocol is intended to provide a AAA framework for Mobile-IP, NASREQ and ROAMOPS. This draft specifies the message format, transport, error reporting and security services to be used by all DIAMETER extensions and MUST be supported by all DIAMETER implementations. Table of Contents 1.0 Introduction 1.1 Requirements language 1.2 Terminology 2.0 Protocol Overview 2.1 Header Format 2.2 AVP Format 2.2.1 AVP Header 2.2.2 Optional Header Elements 2.2.3 AVP Value Formats 2.2.4 DIAMETER Base Protocol AVPs 2.3 Mandatory AVPs 2.3.1 Host-Name AVP 2.4 Grouping of AVPs 2.5 State Machine 2.6 Device-Reboot-Ind (DRI) Command 2.6.1 Vendor-Name AVP 2.6.2 Firmware-Revision AVP 2.6.3 Extension-Id AVP 2.6.4 Host-IP-Address AVP 3.0 "User" Sessions 3.1 Session-Id AVP 3.2 Session-Timeout AVP 3.3 User-Name AVP 3.4 Session Termination 3.4.1 Session-Termination-Ind 3.4.2 Session-Termination-Request 3.4.3 Session-Termination-Answer 4.0 Reliable Transport 5.0 Error Reporting 5.1 Message-Reject-Ind (MRI) Command 5.1.1 Failed-AVP AVP 5.1.2 Unrecognized-Command-Code 5.2 Result-Code AVP 6.0 DIAMETER Message Routing 6.1 NAI-Based Message Routing 6.2 Message Proxying 6.2.1 Proxy-State AVP Calhoun et al. expires March 2001 [Page 2] INTERNET DRAFT September 2000 6.2.2 Destination-NAI AVP 6.3 Message Redirection 6.3.1 Redirected-Host AVP 6.3.2 Redirect-Host-Port AVP 7.0 DIAMETER Message Security 7.1 Hop-by-Hop Security 7.1.1 Integrity-Check-Value AVP 7.1.2 Encrypted-Payload AVP 7.1.2.1 MD5 Payload Hiding 7.2 Nonce AVP 7.3 Timestamp AVP 8.0 IANA Considerations 8.1 AVP Attributes 8.2 Command Code AVP Values 8.3 Extension Identifier Values 8.4 Result-Code AVP Values 8.5 Integrity-Check-Value AVP Transform Values 8.6 AVP Header Bits 9.0 Open Issues 10.0 DIAMETER protocol related configurable parameters 11.0 Security Considerations 12.0 References 13.0 Acknowledgements 14.0 Authors' Addresses 15.0 Full Copyright Statement Calhoun et al. expires March 2001 [Page 3] INTERNET DRAFT September 2000 1.0 Introduction The DIAMETER protocol allows peers to exchange a variety of messages. The base protocol provides the following facilities: - Delivery of AVPs (attribute value pairs) - Capabilities negotiation, as required in [20] - Error notification - Extensibility, through addition of new commands and AVPs, as required in [21] All data delivered by the protocol is in the form of an AVP. Some of these AVP values are used by the DIAMETER protocol itself, while others deliver data associated with particular applications which employ DIAMETER. AVPs may be added arbitrarily to DIAMETER messages, so long as the required AVPs are included and AVPs which are explicitly excluded are not included. AVPs are used by base DIAMETER protocol to support the following required features: - If application-level security is required, all messages MUST include an Integrity Check Vector (ICV). If the ICV is present, the message MUST also carry a timestamp and a nonce to aid in providing replay protection. - To carry user authentication information, for the purposes of enabling the DIAMETER server to authenticate the user. - To allow authorization information to be exchanged for a particular user's session between a DIAMETER client and server. - To exchange resource usage information, which MAY be used for accounting purposes, capacity planning, etc. The DIAMETER base protocol provides the minimum requirements needed for an AAA transport protocol, as required by NASREQ [21], Mobile IP [22, 23], and ROAMOPS [20]. The base protocol is not intended to be used by itself, and must be used with an application-specific extension, such as Mobile IP [10]. The DIAMETER protocol was heavily inspired and builds upon the tradition of the RADIUS [1] protocol. Any node can initiate a request. In that sense, DIAMETER is a peer to peer protocol. In this document, a DIAMETER client is the device that normally initiates a request for authentication and/or authorization of a user. A DIAMETER server is the device that either forwards the request to another DIAMETER server (known as a proxy), or one that performs the actual authentication and/or authorization of the user based on some profile. Given that the server MAY send unsocilited messages to clients, it is possible for the server to also issue authentication requests. However, these are typically in the form of an indication that the user must be re-authenticated and/or re- authorized. Another example of an unsolicited message would be for a Calhoun et al. expires March 2001 [Page 4] INTERNET DRAFT September 2000 request that the client issue an accounting update. DIAMETER services require sequenced in-order reliable delivery of data, with congestion control (receiver windowing). Timely detection of failed or unresponsive peers is also required, allowing for robust operation. TCP is insufficient for this second requirement. DIAMETER SHOULD be transported over SCTP [26]. 1.1 Requirements language In this document, the key words "MAY", "MUST, "MUST NOT", "optional", "recommended", "SHOULD", and "SHOULD NOT", are to be interpreted as described in [13]. 1.2 Terminology Refer to [9] for terminology used in this document. 2.0 Protocol Overview The base DIAMETER protocol is never used on its own. It is always extended for a particular application. Four extensions to DIAMETER are defined by companion documents: NASREQ [7], Mobile IP [10], Accounting Extension [15], Strong Security [11]. These options are introduced in this document but specified elsewhere. Additional extensions to DIAMETER may be defined in the future (see Section 8.3). The base DIAMETER protocol concerns itself with capabilities negotiation, and how messages are sent and how peers may eventually be abandoned. The base protocol also defines certain rules which apply to all exchanges of messages between DIAMETER peers. It is important to note that the base protocol provides optional application-level security AVPs (Integrity-Check-Value) which MAY be used in absence of an underlying security protocol (e.g. IP Security). Communication between DIAMETER peers begins with one peer sending a message to another DIAMETER peer. The set of AVPs included in the message is determined by a particular application of or extension to DIAMETER. We will refer to this as the DIAMETER extension. One AVP that is included to reference a user's session is the Session-Id. The initial request for authentication and/or authorization of a user would include the Session-Id. The Session-Id is then used in all Calhoun et al. expires March 2001 [Page 5] INTERNET DRAFT September 2000 subsequent messages to identify the user's session (see section 3.0 for more information). The communicating party may accept the request, or reject it by returning a response with Result-Code AVP set to indicate an error occured. The specific behavior of the diameter server or client receiving a request depends on the DIAMETER extension employed. Session state (associated with a Session-Id) MUST be freed upon receipt of the Session-Termination-Request, Session-Termination- Answer and according to rules established in a particular extension/application of DIAMETER. Exchanges of messages are either request/reply oriented, or in some special cases, do not require replies. All such messages that do not require replies have names ending with '-Ind' (short for Indication). The DIAMETER base protocol provides the Session-Timeout AVP, which MAY be used by extensions to specify the duration of a specific authorized session. 2.1 Header Format The base DIAMETER protocol is run over SCTP [26] port 1812. Implementations MAY send packets from any source port, but MUST be prepared to receive packets on port 1812. When a request is received, in order to send a reply, the source and destination ports in the reply are reversed. Note that the source and destination addresses used in request and replies MAY be any of the peer's valid IP addresses. A given DIAMETER process SHOULD use the same port number to send all messages to aid in identifying which process sent a given message. More than one DIAMETER process MAY exist within a single host, so the sender's port number is needed to discriminate them. A summary of the DIAMETER data format is shown below. The fields are transmitted in network byte order. Calhoun et al. expires March 2001 [Page 6] INTERNET DRAFT September 2000 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |RADIUS PCC=254 | Flags | Ver | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Command-Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vendor-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVPs ... +-+-+-+-+-+-+-+-+-+-+-+-+- RADIUS PCC The RADIUS Packet Compatibility Code (PCC) field is a one octet field which is used for backward compatibility with RADIUS and MUST be set to 254. In order to easily distinguish DIAMETER messages from RADIUS, the value of 254 has been reserved and allows implementations to support both protocols by using the first octet in the header. Flags The Message Flags field is five bits, and is currently unused. This field MUST be initialized to zero. Version This Version field MUST be set to 1 to indicate DIAMETER Version 1. Message Length The Message Length field is two octets and indicates the length of the DIAMETER message including the header fields. Identifier The Identifier field is four octets, and aids in matching requests and replies. The sender MUST ensure that the identifier in a message is locally unique (to the sender) at any given time, and MAY attempt to ensure that the number is unique across reboots. The identifier is normally a monotonically increasing number, whose start value was randomly generated. DIAMETER servers should consider a message to be unique by examining the source address, source port and Identifier field of the message. Command-Code The Command-Code field is four octets, and is used in order to communicate the command associated with the message. The 32-bit address space is managed by IANA (see section 8.2). The following Calhoun et al. expires March 2001 [Page 7] INTERNET DRAFT September 2000 Command Codes are currently defined in the DIAMETER base protocol and extensions: Command-Name Abbrev. Code Reference -------------------------------------------------------- Device-Reboot-Ind DRI 257 2.6 Message-Reject-Ind MRI 259 5.1 Session-Termination-Ind STI 274 3.4.1 Session-Termination- STR 275 3.4.2 Request Session-Termination- STA 276 3.4.3 Answer AA-Mobile-Node-Request AMR 260 [10] AA-Mobile-Node-Answer AMA 261 [10] Home-Agent-MIP-Request HAR 262 [10] Home-Agent-MIP-Answer HAA 263 [10] AA-Request AAR 265 [7] AA-Answer AAA 266 [7] AA-Challenge-Ind ACI 267 [7] DIAMETER-EAP-Request DER 268 [7] DIAMETER-EAP-Answer DEA 269 [7] DIAMETER-EAP-Ind DEI 270 [7] Accounting-Request ACR 271 [15] Accounting-Answer ACA 272 [15] Accounting-Poll-Ind ACP 273 [15] Accounting-Status-Ind ASI 279 [15] Session-Resource-Query SRQ 277 [29] Session-Resource-Reply SRR 278 [29] Home-Agent-Allocated-Ind HAI 279 [10] Vendor-ID In the event that the Command-Code field contains a vendor specific command, the four octet Vendor-ID field contains the IANA assigned "SMI Network Management Private Enterprise Codes" [2] value. If the Command-Code field contains an IETF standard Command, the Vendor-ID field MUST be set to zero (0). AVPs AVPs is a method of encapsulating information relevant to the DIAMETER message. See section 2.2 for more information on AVPs. 2.2 AVP Format DIAMETER AVPs carry specific authentication, accounting and authorization information, security information as well as configuration details for the request and reply. Calhoun et al. expires March 2001 [Page 8] INTERNET DRAFT September 2000 Some AVPs MAY be listed more than once. The effect of this AVP is specific, and is specified in each case by the AVP description. Each AVP of type 'string' and 'data' MUST be padded to align on a 32 bit boundary, while other AVP types align naturally. NULL bytes are added to the end of the AVP value till a word boundary is reached. The length of the padding is not reflected in the AVP Length field. 2.2.1 AVP Header The AVP format is shown below and MUST be sent in network byte order. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVP Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVP Length | Reserved |P|R|V|R|M| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vendor-ID (opt) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+-+-+-+-+ AVP Code The AVP Code identifies the attribute uniquely. The first 256 AVP numbers are reserved for backward compatibility with RADIUS and are to be interpreted as per NASREQ [7]. AVP numbers 256 and above are used for DIAMETER, which are allocated by IANA (see section 8.1). AVP Length The AVP Length field is two octets, and indicates the length of this Attribute including the AVP Code, AVP Length, AVP Flags, Reserved, the Vendor-ID field if present and the AVP data. If a message is received with an Invalid attribute length, the message SHOULD be rejected. AVP Flags The AVP Flags field informs the DIAMETER host how each attribute must be handled. Note that subsequent DIAMETER extensions MAY define bits to be used within the AVP Header, and an unrecognized bit should be considered an error. The 'R' and the reserved bits are unused and should be set to 0 and ignored on receipt, while the 'P' bit is defined in [11]. The 'M' Bit, known as the Mandatory bit, indicates whether support Calhoun et al. expires March 2001 [Page 9] INTERNET DRAFT September 2000 of the AVP is required. If an AVP is received with the 'M' bit enabled and the receiver does not support the AVP, the message MUST be rejected. AVPs without the 'M' bit enabled are informational only and a receiver that receives a message with such an AVP that is not supported MAY simply ignore the AVP. The 'V' bit, known as the Vendor-Specific bit, indicates whether the optional Vendor-ID field is present in the AVP header. When set the AVP Code belongs to the specific vendor code address space. Unless otherwise noted, AVPs will have the following default AVP Flags field settings: The 'M' bit MUST be set. The 'V' bit MUST NOT be set. 2.2.2 Optional Header Elements The AVP Header consists of several optional fields. These fields are only present if their respective bit-flags are enabled. Vendor-ID The Vendor-ID field is present in the 'V' bit is set in the AVP Flags field. The optional four octet Vendor-ID field contains the IANA assigned "SMI Network Management Private Enterprise Codes" [2] value, encoded in network byte order. Any vendor wishing to implement a DIAMETER extensions MUST use their own Vendor-ID along with their privately managed AVP address space, guaranteeing that they will not collide with any other vendor's extensions, nor with future IETF extensions. A vendor ID value of zero (0) corresponds to the IETF adopted AVP values, as managed by the IANA. Since the absence of the vendor ID field implies that the AVP in question is not vendor specific, implementations SHOULD not use the zero (0) vendor ID. 2.2.3 AVP Value Formats The Data field is zero or more octets and contains information specific to the Attribute. The format and length of the Data field is determined by the AVP Code and AVP Length fields. The format of the value field MAY be one of seven data types. Data The data contains a variable length of arbitrary data. Unless otherwise noted, the AVP Length field MUST be set to at least 9. Calhoun et al. expires March 2001 [Page 10] INTERNET DRAFT September 2000 String The data contains a non-NULL terminated variable length string using the UTF-8 [24] character set. Unless otherwise noted, the AVP Length field MUST be set to at least 9. Address 32 bit (IPv4) [17] or 128 bit (IPv6) [16] address, most significant octet first. The format of the address (IPv4 or IPv6) is determined by the length. If the attribute value is an IPv4 address, the AVP Length field MUST be 12, otherwise the AVP Length field MUST be set to 24 for IPv6 addresses. Integer32 32 bit value, in network byte order. The AVP Length field MUST be set to 12. Integer64 64 bit value, in network byte order. The AVP Length field MUST be set to 16. Time 32 bit unsigned value contains the four most significant octets returned from NTP [18], in network byte order. The AVP Length field MUST be set to 12. Complex The complex data type is reserved for AVPs that includes multiple information fields, and therefore do not fit within any of the AVP types defined above. Complex AVPs MUST provide the data format, and the expected length of the AVP. 2.2.4 DIAMETER Base Protocol AVPs The following table describes the DIAMETER AVPs defined in the base protocol, their AVP Code values, types, possible flag values and whether the AVP MAY be encrypted. Calhoun et al. expires March 2001 [Page 11] INTERNET DRAFT September 2000 +---------------------+ | AVP Flag rules | |----+-----+----+-----|----+ AVP Section Value | | |SHLD| MUST|MAY | Attribute Name Code Defined Type |MUST| MAY | NOT| NOT|Encr| -----------------------------------------|----+-----+----+-----|----| User-Name 1 3.3 String | | | | | Y | Session-Timeout 27 3.2 Integer32| | | | | Y | Proxy-State 33 6.2.1 Complex | M | | | V | N | Host-IP-Address 257 2.6.4 Address | M | | | V | N | Extension-Id 258 2.6.3 Integer32| | | | | Y | Integrity-Check 259 7.1.1 Complex | | | | | N | -Value | | | | | | Encrypted- 260 7.1.2 Complex | | | | | N | Payload | | | | | | Nonce 261 7.2 Data | | | | | N | Timestamp 262 7.3 Time | | | | | N | Session-Id 263 3.3 Data | | | | | Y | Host-Name 264 2.3.2 String | M | | | V | N | Vendor-Name 266 2.6.1 String | | | | V,M | Y | Firmware 267 2.6.2 Integer32| | | | V,M | Y | -Revision | | | | | | Result-Code 268 5.2 Complex | | | | | N | Destination-NAI 269 6.2.2 String | | | | | Y | Unknown-Command- 270 5.1.2 Integer32| | | | | Y | Code | | | | | | Failed-AVP 279 5.1.1 Data | | | | | Y | Redirect-Host 278 6.3.1 Address | | | | | Y | Redirect-Host- 277 6.3.2 Integer32| | | | | Y | Port | | | | | | Grouped-AVP 280 2.4.1 Data | M | | | V | Y | 2.2.5 Standard DIAMETER Extension AVPs The following AVPs are defined in standard DIAMETER extensions. Calhoun et al. expires March 2001 [Page 12] INTERNET DRAFT September 2000 AVP Name Code Ref AVP Name Code Ref AVP Name Code Ref ------------- ---- --- ------------ ---- --- ------------ ---- ---- User-Password 2 [7] Framed- 38 [7] MN-FA- 322 [10] CHAP-Password 3 [7] Appletalk- Challenge- NAS-IP-Address 4 [7] Network Length NAS-Port 5 [7] Framed- 39 [7] MN-FA-Response 323 [10] Service-Type 6 [7] Appletalk- Mobile-Node- 333 [10] Framed-Protocol 7 [7] Zone Address Framed-IP- 8 [7] CHAP-Challenge 60 [7] Home-Agent- 334 [10] Address NAS-Port-Type 61 [7] Address Framed-IP- 9 [7] Port-Limit 62 [7] Previous-FA- 335 [10] Netmask Login-LAT-Port 63 [7] NAI Framed-Routing 10 [7] Tunnel-Type 64 [7] MN-AAA-SPI 336 [10] Filter-Id 11 [7] Tunnel-Medium- 65 [7] Foreign-Home- 337 [10] Framed-MTU 12 [7] Type Agent- Framed- 13 [7] Tunnel-Client- 66 [7] Available Compression Endpoint Filter-Rule 400 [7] Login-IP-Host 14 [7] Tunnel-Server- 67 [7] Request-Type 401 [7] Login-Service 15 [7] Endpoint EAP-Payload 402 [7] Login-TCP-Port 16 [7] Tunnel-Password 69 [7] Accounting- 480 [15] Reply-Message 18 [7] Tunnel-Private- 81 [7] Record-Type Callback-Number 19 [7] Group-ID ADIF-Record 481 [15] Callback-Id 20 [7] Tunnel- 82 [7] Accounting- 482 [15] Framed-IP-Route 22 [7] Assignment-ID Interim- Framed-IPX- 23 [7] Tunnel- 83 [7] Interval Route Preference Accounting- 483 [15] Idle-Timeout 28 [7] Tunnel-Client- 90 [7] Delivery- Called-Station- 30 [7] Auth-ID Interval Id Tunnel-Server- 91 [7] Accounting- 484 [15] Calling- 31 [7] Auth-ID Delivery- Station-Id CMS-Data 310 [11] Max-Delay NAS-Identifier 32 [7] MIP- 320 [10] Accounting- 485 [15] Login-LAT- 34 [7] Registration- Record- Service Request Number Login-LAT-Node 35 [7] MIP- 321 [10] Accounting- Login-LAT-Group 36 [7] Registration- State 486 [15] Framed- 37 [7] Reply Query-Index 500 [29] Appletalk- Resource-Token 501 [29] Link 2.3 Mandatory AVPs This section defines the DIAMETER AVPs that MUST be present in all DIAMETER messages. 2.3.1 Host-Name AVP Calhoun et al. expires March 2001 [Page 13] INTERNET DRAFT September 2000 The Host-Name AVP (AVP Code 264) [1] is of type String, and is used to inform a DIAMETER peer of the sender's identity. All DIAMETER messages MUST include the Host-Name AVP, which contains the host name of the originator of the DIAMETER message that MUST follow the NAI [8] naming conventions. Note that the Host-Name AVP may resolve to more than one address as the DIAMETER peer may support more than one address. 2.4 Grouping of AVPs The DIAMETER protocol allows AVPs to be "grouped" into a set, allowing for complex data representation. The Grouped-AVP AVP encapsulates more than one AVP to form an AVP set. Multiple layers of encapsulation MAY be used by including a child Grouped-AVP AVP inside a parent Grouped-AVP AVP. An example of the use of the Grouped-AVP AVP is the Redirect-Host AVP (see section 6.3.1), which is used by brokers to request that a DIAMETER message be redirected to another DIAMETER node. Since it is possible for a DIAMETER node to listen for incoming messages other than on the default (standard) port, the Redirect-Host-Port AVP (section 6.3.2) allows the port number to be communicated as well. The Grouped-AVP MAY be used to create a logical set of the Host and the port number, thereby allowing the broker to return more than one set of hosts which the message could be redirected to. The following is the BNF representation of the above example: ::= }> }> 2.4.1 Grouped-AVP AVP The Grouped-AVP AVP (AVP Code 280) is of type complex and is used to encapsulate multiple AVPs creating an AVP set. Calhoun et al. expires March 2001 [Page 14] INTERNET DRAFT September 2000 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ AVP Header (AVP Code = 280) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVPs... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ AVPs The AVPs field contains the encapsulated AVPs. 2.5 State Machine This section contains a finite state machine, that MUST be observed by all DIAMETER implementations. Each DIAMETER node MUST follow the state machine described below when communicating with each peer. State Event Action New State ----- ----- ------ --------- Initial Local request to establish SCTP Idle communication with a DIAMETER Connect peer with which there is no existing transport level connection established. Initial Receive transport level Send DRI Open connection request from a DIAMETER peer. Idle Connection Established Send DRI Wait-DRI Idle Receive DRI Send DRI Open Wait-DRI Receive DRI None Open Open Receive other messages Process Open Message Open Receive DRI Cleanup Closed Open Transport level failure Cleanup Closed Closed DIAMETER Entity shutdown Close Initial or close connection with peer connection The Initial and Idle states MAY be merged if the local SCTP implementation is able to implement the piggyback of data during the Calhoun et al. expires March 2001 [Page 15] INTERNET DRAFT September 2000 connection phase. When the Cleanup action is invoked, the DIAMETER node SHOULD attempt to forward all pending requests and replies, which haven't been acknowledged, to an alternate server (when possible). If the final destination for a specific message is the host that is no longer accessible, the message in question SHOULD be responded with the Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. 2.6 Device-Reboot-Ind (DRI) Command A DIAMETER device sends the Device-Reboot-Ind message, by setting the Command-Code field with a value of 257, to inform a peer that a reboot has just occured. Since SCTP [26] allows for connections to span multiple interfaces, hence multiple IP addresses, the Device- Reboot-Ind message MUST contain one Host-IP-Address AVP for each potential IP address that MAY be locally used when transmitting DIAMETER messages. The DRI message is also used for capabilities negotiation, such as the supported protocol version number, and the locally supported extensions. The receiver uses the extensions advertised in order to determine whether it SHOULD send certain application-specific DIAMETER commands. A DIAMETER node MUST retain the supported extensions in order to ensure that unrecognized commands and/or AVPs are not sent to a peer. Note that in a proxy environment, it is still possible that a downstream proxy has no available peer that have advertised the extension that corresponds to the Command-Code, and therefore the request cannot be forwarded any further. The DIAMETER base protocol provides this error reporting, via the Result-Code AVP. Once the transport layer connection has been established, a DIAMETER entity MUST issue a DRI message, regardless of whether the peer was statically configured, or dynamically discovered. Dynamic discovery of DIAMETER peers MAY be done by using Service Location Protocol (SLP) [28], or through some other discovery mechanism. If a peer is no longer reachable, a DIAMETER device SHOULD periodically attempt to establish a transport level connection with the peer and send a DRI message. This message does not require a reply. If a DIAMETER node receives a DRI message that results in an error, a Message-Reject-Ind message MUST be returned. Message Format Calhoun et al. expires March 2001 [Page 16] INTERNET DRAFT September 2000 ::= [] [ ] 2.6.1 Vendor-Name AVP The Vendor-Name AVP (AVP Code 266) is of type String and is used to inform a DIAMETER peer of the Vendor Name of the DIAMETER device. This MAY be used in order to know which vendor specific attributes may be sent to the peer. It is also envisioned that the combination of the Vendor-Name and the Firmware-Revision (section 2.6.2) AVPs MAY provide very useful debugging information. 2.6.2 Firmware-Revision AVP The Firmware-Revision AVP (AVP Code 267) is of type Integer32 and is used to inform a DIAMETER peer of the firmware revision of the issuing device. For devices that do not have a firmware revision (general purpose computers running DIAMETER software modules, for instance), the revision of the DIAMETER software module may be reported instead. 2.6.3 Extension-Id AVP The Extension-Id AVP (AVP Code 258) is of type Integer32 and is used in order to identify a specific DIAMETER extension. This AVP is used in the Device-Reboot-Ind message in order to inform the peer what extensions are locally supported. Each DIAMETER extension draft MUST have an IANA assigned extension Idenfier (see section 8.3). The base protocol does not require an Extension-Id since its support is mandatory. There MAY be more than one Extension-Id AVP within a DIAMETER Device-Reboot-Ind message. The following values are recognized: NASREQ 1 [7] Strong Security 2 [11] Calhoun et al. expires March 2001 [Page 17] INTERNET DRAFT September 2000 Resource Management 3 [29] Mobile-IP 4 [10] Accounting 5 [15] 2.6.4 Host-IP-Address AVP The Host-IP-Address AVP (AVP Code 4) [1] is of type Address and is used to inform a DIAMETER peer of the sender's IP addresses. All source addresses that a DIAMETER node expects to use with SCTP [26] MUST be advertised in the Device-Reboot-Ind message by including a Host-IP-Address AVP for each address. This AVP MUST ONLY be used in the Device-Reboot-Ind message. 3.0 "User" Sessions When a user requests access to the network, a DIAMETER client issues an authentication and authorization request to its local server. The request contains a Session-Id AVP, which is used in subsequent messages (e.g. subsequent authorization, accounting, etc) relating to the user's session. The Session-Id AVP is a means for the client and servers to correlate a DIAMETER message with a user session. When a DIAMETER server authorizes a user to use network resources, it SHOULD add the Session-Timeout AVP to the response. The Session- Timeout AVP defines the maximum amount of time a user MAY make use of the resources before another authorization request is to be transmitted to the server. If the server does not receive another authorization request before the timeout occurs, it SHOULD release any state information related to the user's session. Note that the Session-Timeout AVP implies how long the DIAMETER server is willing to pay for the services rendered, therefore a DIAMETER client SHOULD NOT expect payment for services rendered past the session expiration time. The base protocol does not include any authorization request messages, since these are largely application-specific and are defined in a DIAMETER protocol extension document. However, the base protocol does define a set of messages that are used to terminate user sessions. These are used to allow servers that maintain state information to free resources. 3.1 Session-Id AVP The Session-Id AVP (AVP Code 263) is of type Data and is used to identify a specific session (see section 3.0). All messages Calhoun et al. expires March 2001 [Page 18] INTERNET DRAFT September 2000 pertaining to a specific session MUST include only one Session-Id AVP and the same value MUST be used throughout the life of a session. When present, the Session-Id SHOULD appear immediately following the DIAMETER Header (see section 2.1). For messages that do not pertain to a specific session, multiple Session-Id AVPs MAY be present as long as they are encapsulated within different Grouped-AVP AVPs. The Session-Id MUST be globally unique at any given time since it is used by the server to identify the session (or flow). The format of the session identifier SHOULD be as follows: The monotonically increasing 32 bit value SHOULD NOT start at zero upon reboot, but rather start at a random value. This will minimize the possibility of overlapping Session-Ids after a reboot. Alternatively, an implementation MAY keep track of the increasing value in non-volatile memory. The optional value is implementation specific but may include a modem's device Id, a layer 2 address, timestamp, etc. The session Id is created by the DIAMETER device initiating the session, which in most cases is done by the client. Note that a Session-Id MAY be used by more than one extension (e.g. authentication for a specific service and accounting, both of which have separate extensions). 3.2 Session-Timeout AVP The Session-Timeout AVP (AVP Code 27) [1] is of type Integer32 and contains the maximum number of seconds of service to be provided to the user before termination of the session. A value of zero means that this session has an unlimited number of seconds before termination. This AVP MAY be provided by the client as a hint of the maximum duration that it is willing to accept. However, the server DOES NOT have to observe the hint, and MAY return a value that is smaller than the hint. A value of zero provided by a client DOES NOT imply that service is being terminated. 3.3 User-Name AVP Calhoun et al. expires March 2001 [Page 19] INTERNET DRAFT September 2000 The User-Name AVP (AVP Code 1) [1] is of type String and contains the User-Name in a format consistent with the NAI specification [8]. All DIAMETER systems SHOULD support usernames of at least 72 octets in length. 3.4 Session Termination The DIAMETER Base Protocol provides a set of messages that MAY be used by any peer to explicitely request that a previously authenticated and/or authorized session be terminated. Since the Session-Id is typically tied to a particular service (i.e. Mobile IP, NASREQ, etc), the session termination messages are used to request that the service tied to the Session Id be terminated. 3.4.1 Session-Termination-Ind The Session-Termination-Ind (STI), indicated by the Command-Code set to 274, MAY be sent by any DIAMETER entity to the access device to request that a particular session be terminated. This message MAY be used when a server detects that a session MUST be terminated, which is typically done as a policy decision (e.g. local resources have been expended, etc). The Destination-NAI AVP MUST be present, and contain the NAI of the access device that initiated the session (see section 3.0). Upon receipt of the STI message, the access device SHOULD issue a Session-Terminate-Request message. Message Format ::= [] [ ] 3.4.2 Session-Termination-Request The Session-Termination-Request (STR), indicated by the Command-Code set to 275, is sent by the access device to inform the Home AAA that an authenticated and/or authorized session is being terminated. The Calhoun et al. expires March 2001 [Page 20] INTERNET DRAFT September 2000 Destination-NAI AVP MUST be present, and set to the value that was found in the Host-Name AVP of the authentication and/or authorization response that corresponds with the session in question (e.g. AAA, HAR, AMA in section 2.1). Upon receipt of the STR, the Home DIAMETER Server SHOULD release all resources for the session indicated by the Session-Id AVP. Any intermediate server in the Proxy-Chain MAY also release any resources, if necessary. Message Format ::= [] [ ] 3.4.3 Session-Termination-Answer The Session-Termination-Answer (STA), indicated by the Command-Code set to 276, is sent by the Home DIAMETER Server to acknowledge that the session has been terminated. The Result-Code AVP MUST be present, and MAY contain an indication that an error occured while servicing the STR. Message Format ::= [] [ ] 4.0 Reliable Transport Calhoun et al. expires March 2001 [Page 21] INTERNET DRAFT September 2000 In order to provide rapid discovery of the failure of a communicating peer, aggressive retransmission and rapid transactions, DIAMETER peers MUST be able to send and receive messages over SCTP [26]. A DIAMETER peer MAY use TCP [27], as TCP does provide reliable transport, though it does not have the properties listed above. 5.0 Error Reporting There are five different types of errors within DIAMETER. The first being where a DIAMETER message is poorly formatted and unrecognizable, indicated below by "Bad Message". This error condition applies if a received message creates a fatal error (e.g. fails transport level authentication, cannot be parsed, etc). The second case involves receiving a Command-Code that is not supported, which is shown below by "Unknown Command". The third case is where an AVP is received, marked mandatory and is unknown by the receiver, which is labeled below as "Unknown AVP". This fourth case involves receiving a message with a known AVP, yet the value is either unknown or illegal, which is shown below as "Bad Value". The last case occurs when an error occurs while processing a specific extension command, which is not related to the message format and is labeled "Extension Error" below. Error Type Ignore Message Send Extension Message-Reject-Ind Response + Result-Code Bad Message X Unknown Command X Unknown AVP X Bad Value X Extension Error X "Ignore Message" indicates that the message is simply dropped. The "Message-Reject-Ind" indicates that a Message-Reject-Ind message MUST be sent to the peer as described in the appropriate section. The "Extension Response + Result-Code" indicates that the appropriate Response to the message MUST be sent with the Result-Code AVP set to a value that enables the peer to understand the nature of the problem. 5.1 Message-Reject-Ind (MRI) Command The Message-Reject-Ind (MRI), indicated by the Command-Code set to 259, provides a generic means of completing transactions by Calhoun et al. expires March 2001 [Page 22] INTERNET DRAFT September 2000 indicating errors in the messages that initiated them. The Message- Reject-Ind command is sent in response: 1. An error is found in a Device-Reboot-Ind message. 2. An error is found in a message for which there is no appropriate response. 3. A message was received that cannot pass the base protocol error checking. 4. A message was received whose extension is not locally supported. In the event that a request is received that causes an error defined in a DIAMETER extension, the appropriate response with the Result- Code AVP SHOULD be sent. The Message-Reject-Ind message MUST contain the same identification in the header and include the Session-Id if it was present in the original message that it is responding to, even if the identification is erroneous. Message Format The structure of the Message-Reject-Ind message is defined as follows: ::= [] [ ] where the Identifier value in the message header and optionally the Session-Id AVP are copied from the message being rejected. The Result-Code AVP indicate the nature of the error causing rejection, and the Failed-AVP AVP provides some minimal debugging data by indicating a specific AVP type which caused the problem. See the description of the Result-Code AVP for indication of when the Failed-AVP AVP MUST be present in the message. See [25] for more information. 5.1.1 Failed-AVP AVP The Failed-AVP AVP (AVP Code 279) is of type Data and provides Calhoun et al. expires March 2001 [Page 23] INTERNET DRAFT September 2000 debugging information in cases where a request is rejected or not fully processed due to erroneous information in a specific AVP. The value of the Result-Code AVP will provide information on the reason for the Failed-AVP AVP. A DIAMETER message MAY contain one or more Failed-AVP, each containing a complete AVP that could not be processed successfully. The possible reasons for this AVP are the presence of an improperly constructed AVP, an unsupported or unrecognized AVP or an invalid AVP value. 5.1.2 Unrecognized-Command-Code The Unrecognized-Command-Code AVP (AVP Code 270) is of type Integer32 and contains the offending Command-Code that resulted in sending the Message-Reject-Ind message. 5.2 Result-Code AVP The Result-Code AVP (AVP Code 268) is of type Complex and indicates whether a particular request was completed successfully or whether an error occurred. All DIAMETER messages of type *-Response or *-Answer MUST include one Result-Code AVP. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ AVP Header (AVP Code = 268) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Result Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | String ... +-+-+-+-+-+-+-+-+ The Result Code field contains an IANA-managed 32-bit address space representing errors (see section 8.4). The String field contains an OPTIONAL string field containing a human readable error message. The base protocol defines the following error codes, and others MAY be defined in separate DIAMETER extensions: DIAMETER_SUCCESS 0 The Request was successfully completed. DIAMETER_FAILURE 1 The Request was not successfully completed for an unspecified Calhoun et al. expires March 2001 [Page 24] INTERNET DRAFT September 2000 reason. A DIAMETER Message-Reject-Ind message returning this result SHOULD whenever possible also contain one or more Failed-AVP AVPs indicating the AVPs that caused the failure. DIAMETER_POOR_REQUEST 2 The Request was poorly constructed. DIAMETER_INVALID_AUTH 3 The Request did not contain a valid Integrity-Check-Value or CMS-Data [11] AVP. DIAMETER_UNKNOWN_SESSION_ID 4 The request or response contained an unknown Session-Id. DIAMETER_USER_UNKNOWN 5 A request was received for a user that is unknown, therefore authentication failed. This error is sent only due to conditions that arise due to command messages in DIAMETER extensions, the base protocol does not include command codes that require the User-Name AVP. DIAMETER_COMMAND_UNSUPPORTED 6 The Request contained a Command-Code that the receiver did not recognize or support. The Message-Reject-Ind message MUST also contain a Unknown-Command-Code AVP containing the unrecognized Command-Code. DIAMETER_TIMEOUT 7 This error MAY be returned if a request has been received that has a Timestamp AVP that is older than the maximum age that the communicating peer is willing to accept. DIAMETER_AVP_UNSUPPORTED 8 The peer received a message that contained an AVP that is not recognized or supported and was marked with the Mandatory bit. A DIAMETER message with this error MUST contain one or more Failed-AVP AVP containing the AVPs that caused the failure. DIAMETER_REDIRECT_INDICATION 9 A proxy or broker has determined that the request could not be satisfied locally and the initiator of the request should direct the request directly to the server, whose contact information has been added to the response. This error code MUST NOT be sent in a Message-Reject-Ind message. DIAMETER_REALM_NOT_SERVED 10 A proxy or broker has determined that it is unable to forward the request or provide redirect information since the realm Calhoun et al. expires March 2001 [Page 25] INTERNET DRAFT September 2000 portion of the NAI requested is unknown. DIAMETER_UNSUPPORTED_TRANSFORM 11 A message was received that included an Integrity-Check-Value or CMS-Data AVP [11] that made use of an unsupported transform. DIAMETER_AUTHENTICATION_REJECTED 12 The authentication process for the user failed, most likely due to an invalid password used by the user. DIAMETER_AUTHORIZATION_REJECTED 13 A request was received for which the user could not be authorized. This error could occur when the user has already expended allowed resources, or if the service requested is not permitted to the user. DIAMETER_INVALID_AVP_VALUE 14 The request contained an AVP with an invalid value in its data portion. A DIAMETER message with this result code MUST include the offending AVPs within a Failed-AVP AVP. DIAMETER_MISSING_AVP 15 The request did not contain an AVP that is considered mandatory by the Command Code definition. If this value is sent in the Result-Code AVP, a Failed-AVP AVP SHOULD be included in the message. The data portion of the Failed-AVP MUST have its AVP Code set to the value of the missing AVP. DIAMETER_UNABLE_TO_DELIVER 16 The request could not be delivered to the host specified in the Destination-NAI AVP, or no host is available for that particular realm to handle the request. 5.2.1 Additional Error Codes The following additional result codes are defined by standard extensions to the DIAMETER protocol. DIAMETER_ERROR_BAD_KEY 16 [10] DIAMETER_ERROR_BAD_HOME_ADDRESS 17 [10] DIAMETER_ERROR_TOO_BUSY 18 [10] DIAMETER_ERROR_MIP_REPLY_FAILURE 19 [10] DIAMETER_INVALID_CMS_DATA 20 [11] 6.0 DIAMETER Message Routing Calhoun et al. expires March 2001 [Page 26] INTERNET DRAFT September 2000 The DIAMETER base protocol supports two basic message routing methods; proxying and brokering. A DIAMETER proxy is a server that simply forwards the request based on the user's identity, or through some other means. A DIAMETER broker is a server that provides redirect services, allowing all servers in a roaming consortium to interact directly. This section describes how DIAMETER message routing is performed. 6.1 NAI-Based Message Routing DIAMETER Message routing is done through the use of the Network Access Identifier (NAI), and an associated realm routing table (see section 10.0). The NAI has a format of user@realm, and DIAMETER servers have a list of locally supported realms, and MAY have a list of externally supported realms. When a message is received that includes a realm that is not locally supported, the message is proxied to the DIAMETER entity configured in the "route" table. Figure 1 depicts an example where DIA1 receives a request to authenticate user "joe@abc.com". DIA1 looks up "abc.com" in its local realm route table and determines that the message must be proxied to DIA2. DIA2 does the same check, and proxies the message to DIA3. DIA3 checks its realm route table, and determines that the realm is locally supported, and processes the authentication request, and returns the response. How the response actually makes it back to the sender of the original request is described in the next section. (Request) (Request) (User-Name=joe@abc.com) (User-Name=joe@abc.com) +------+ ------> +------+ ------> +------+ | | | | | | | DIA1 +-------------------+ DIA2 +-------------------+ DIA3 | | | | | | | +------+ <------ +------+ <------ +------+ (Response) (Response) (User-Name=joe@abc.com) (User-Name=joe@abc.com) mno.net xyz.com abc.com Figure 1: NAI Based Routing 6.2 Message Proxying A DIAMETER proxy is a server that provides message forwarding functions to other DIAMETER Servers. Proxies are typically used when a hierarchical DIAMETER network is deployed, where some DIAMETER servers can authenticate and authorize a set of users. Such an Calhoun et al. expires March 2001 [Page 27] INTERNET DRAFT September 2000 example is a roaming consortium, where each ISP has a user base, which they can authenticate and authorize. It is important to note that proxy servers MUST NOT attempt to re-order AVPs in a DIAMETER message. There are two different methods of routing DIAMETER messages through proxies; Proxy-State and Destination-NAI. The Proxy-State AVP is used to encode local state information in a request. The corresponding response is guaranteed to include the same Proxy-State AVP, allowing the node to recover the state information. The use of the Proxy-State AVP requires that the corresponding response traverse through the same set of proxies (in reverse order), which introduces some reliability problems. If a single DIAMETER node in the proxy chain fails, all responses that must traverse through it would be lost. The Proxy-State AVP is used by proxy servers that MUST maintain state information, such as protocol translation gateways [25]. The Destination-NAI is a more flexible scheme, and is used by DIAMETER proxies that do not need to maintain any state information when acting as a simple message routing agent. This allows the DIAMETER network to be much more reliable, since responses can be sent through an alternate path should a proxy server fail. 6.2.1 Proxy-State AVP The Proxy-State AVP (AVP Code 33) [1] is used by proxy servers when forwarding requests and contains opaque data that is used by the proxy to further process the response. Such data may include AVPs that are to be added to the response, information about the downstream peer, etc. It is important to note that the use of the Proxy-State AVP requires that the corresponding response traverse through the DIAMETER node that added the AVP. The requirement that responses return on the reverse path of a request is only adequate in certain networks. It does not allow for resilient operation, since alternative servers MUST NOT be used. Therefore a DIAMETER node SHOULD only use the Proxy-State AVP when performing protocol bridging [25]. A DIAMETER node that adds a Proxy-State AVP to a request expects the SAME AVP to be present in the corresponding response. Furthermore, more than one Proxy-State AVP MUST NOT be present in a single DIAMETER message. See [25] for more information on AVP handling. Calhoun et al. expires March 2001 [Page 28] INTERNET DRAFT September 2000 (Request) (Request) (User-Name=joe@abc.com) (User-Name=joe@abc.com) (Proxy-State=DIA1,x) (Proxy-State=DIA2,y) +------+ ------> +------+ ------> +------+ | | | | | | | DIA1 +-------------------+ DIA2 +-------------------+ DIA3 | | | | | | | +------+ <------ +------+ <------ +------+ (Response) (Response) (User-Name=joe@abc.com) (User-Name=joe@abc.com) (Proxy-State=DIA1,x) (Proxy-State=DIA2,y) mno.net xyz.com abc.com Figure 2: Use of the Proxy-State AVP When a DIAMETER node receives a message that includes the Proxy-State AVP, and the address within the AVP is a peer that it is able to exchange DIAMETER messages with, the message MUST be forwarded to the peer in question. When the Proxy-State AVP's address indicates that the AVP was locally added, the Proxy-State AVP MUST be removed, and the original Proxy-State AVP must be restored (if one was present in the corresponding request). When DIA2 receives the response from DIA3 (in figure 2), it examines the Proxy-State and finds that it was created by DIA1. Since DIA2 is able to communicate with DIA1, it forwards the message to DIA1. The Proxy-State AVP's Address field is 128-bits in length contains one of the IP addresses of the system that created the AVP, and used to assist hosts in determining whether a Proxy-State AVP is intended for the local host. If the host creating the AVP has an IPv4 address, and is IPv6 capable, the leading 96 bits MUST be set to zero (0). If the AVP has an IPv4 address, and the host is not IPv6 capable, the leading 64 bites MUST be set to zero (0), and the following 32 bits MUST be set to all ones [16]. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ AVP Header (AVP Code = 33) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 128-bit Address... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+-+-+-+-+ 6.2.2 Destination-NAI AVP Calhoun et al. expires March 2001 [Page 29] INTERNET DRAFT September 2000 The Destination-NAI AVP (AVP Code 269) is of type String, MAY be included in a request, and SHOULD be included in a response message. The Destination-NAI MUST be in a format consistent with the NAI specification. When found in a response, the AVP SHOULD contain the value of the Host-Name AVP that was found in the request. Since the Destination-NAI AVP allows for a more resilient DIAMETER network, by allowing a DIAMETER node to send to one of many peers that can handle a particular realm, implementations SHOULD use it as opposed to the Proxy-State AVP. Request messages in transactions that span multiple round trips (e.g. EAP [7]), the Destination-NAI AVP SHOULD be copied from the previous response that caused the new request. This will ensure that all requests forming the transaction will be forwarded to the same target DIAMETER server. (Request) (Request) (User-Name=joe@abc.com) (User-Name=joe@abc.com) (Host-Name=DIA1@nmo.net) (Host-Name=DIA1@nmo.net) +------+ +------+ +------+ | | | | | | | DIA1 +------------------>+ DIA2 +------------------>+ DIA3 | | | | | | | +------+ +------+ +------+ ^ | | +------+ | | | | | +-----------------------| DIA4 |<----------------------+ | | +------+ (Response) (Response) (User-Name=joe@abc.com) (User-Name=joe@abc.com) (Dest-NAI=DIA1@mno.net) (Dest-NAI=DIA1@mno.net) mno.net mno.com abc.com Figure 3: Use of Destination-NAI When DIA3 (in figure 3) creates the response, it adds the Destination-NAI AVP with the value that was found in the request's Host-Name AVP. DIA3 is not able to communicate directly with DIA1, but it is able to communicate with peers within the mno.com network. Therefore, it issues the response to any peer in the mno.com network. When DIA4 receives the response, it examines the Destination-NAI AVP, and determines that it is able to communicate directly with DIA1, and forwards the response to it. Calhoun et al. expires March 2001 [Page 30] INTERNET DRAFT September 2000 6.3 Message Redirection There are cases where a DIAMETER proxy, known as a broker, may wish to request that a server contact another directly instead of forwarding the message (figure 2). This is typically done when the broker provides simple NAI to Home DIAMETER Server address resolution services. In the example provided in figure 4, abc.net's DIAMETER server issues a request to its broker, which in turn returns a response that includes the Result-Code AVP set to DIAMETER_REDIRECT_INDICATION (see section 5.2). When a response is received with the Result-Code set to this value, the message MUST also include one or more Redirect- Host AVPs, and optionally the Redirect-Host-Port AVP. The Redirect- Host AVP contains the IP address to which the request SHOULD be forwarded to directly. When more than one un-grouped Redirect-Host- Port AVPs are found, they contain more than one server that could service the request. When more than one Redirect-Host AVP is present in a Grouped-AVP, they contain the various IP addresses of the SAME host, any of which MAY be used to directly contact the peer. The above requires that the broker be contacted for all messages in order to identify the Home DIAMETER server to use for a particular realm. Since contacting the broker does introduce additional latency, an implementation MAY cache the information received by the broker, eliminating the need to contact the broker for multiple messages to the same realm. The broker MAY include the the Session-Timeout AVP in the redirect response as a hint to its peer as to how long the cache entry SHOULD be valid. The peer is not obligated to respect the hint from the broker. In the event that the Redirect-Host AVP is grouped, the broker MAY also include the Session-Timeout AVP to the same Grouped-AVP in order to specify the cache timeout for the particular host. +------------------+ +---------+ | DIAMETER | | CRL DB/ | | Broker | | OCSP | +------------------+ +---------+ ^ Request | Response + | Result Code = | Redirect v +----------+ +----------+ | abc.net | | xyz.net | | DIAMETER |<------------>| DIAMETER | | Server | | Server | Calhoun et al. expires March 2001 [Page 31] INTERNET DRAFT September 2000 +----------+ Direct +----------+ Communication Figure 4: DIAMETER Broker Returning Redirect Indication When returning the response with the Result-Code set to DIAMETER_REDIRECT_INDICATION, the broker MAY also include the certificates of both the requesting server, and the target server. These certificates are encapsulated in a CMS-Data AVP [11]. The requesting server SHOULD forward the certificate that belongs to it in the subsequent request to the home DIAMETER server. Figure 5 below provides a more complex network, where the request must be forwarded to a second broker (Inter-Broker Communication), and there are a number of proxies between the NAS and the "edge" DIAMETER Server that communicates with the broker. When Broker A receives the response that includes the redirect information from Broker B, it is passed down to abc's DIAMETER server, which in turn communicates directly with xyz's server. +------------+ Request +------------+ | DIAMETER | | DIAMETER | | Broker A |<--------->| Broker B | +------------+ Redirect +------------+ ^ Response Request |Redirect |Response | v +----------+ +----------+ +-----+ +-| abc.net | | xyz.net | | | +-| | DIAMETER |<------------>| DIAMETER | | NAS |<->| | | Server(s)| | Server | | | | | +----------+ Direct +----------+ +-----+ | +----------+ Communication +----------+ Figure 5: Inter-Broker redirect in a proxied network 6.3.1 Redirect-Host AVP The Redirect-Host AVP (AVP Code 278) is of type Address and is returned in a response that has the Result-Code AVP set to DIAMETER_REDIRECT_REQUEST. This AVP includes the IP address of the DIAMETER host to which the request MUST be redirected. The presence of multiple Redirect-Host AVPs within the same Grouped-AVP, implies that all of the addresses MAY be used to contact the same host. When multiple AVPs are found that are un-grouped, or grouped with different Grouped-AVPs, they represent separate hosts. Upon receipt Calhoun et al. expires March 2001 [Page 32] INTERNET DRAFT September 2000 of such a Result-Code, and this AVP, a DIAMETER host SHOULD send the request directly to one of the hosts. The broker MAY wish to return the certificate associated with a given Redirect-Host AVP. This can be returned in a CMS-Data AVP, as defined in [11]. 6.3.2 Redirect-Host-Port AVP The Redirect-Host-Port AVP (AVP Code 277) is of type Integer32 and MAY be present when the Redirect-Host AVP is present. The absence of this AVP implies that the reserved port MUST be used. 7.0 DIAMETER Message Security The DIAMETER Base protocol MAY be secured in one of three ways. The first method does not involve any security mechanisms in the DIAMETER protocol, but relies on an underlying security mechanism, such as IP Security. The second method is hop-by-hop security, which SHOULD be supported by all DIAMETER implementations. The third method is optional and requires a Public Key Infrastructure [14], and is documented in [11]. 7.1 Hop-by-Hop Security DIAMETER Hop-by-Hop security provides message integrity and per AVP encryption, and requires that the communicating entities have a pre- configured shared secret, similar to the method employed by the RADIUS protocol. Hop-by-Hop security is very difficult to deploy and administer in large scale networks and involves symmetric trust, unlike security based on a public key infrastructure (PKI). PKI is used for DIAMETER End-to-End security, and is defined in [11]. Hop- by-Hop security may be desirable in environments where symmetric cryptography is sufficient or when a PKI is not available. Figure 6 below provides an example of hop-by-hop security in a proxy chain. Assuming that the packet was received by DIA2 from DIA1, and was to be proxied to DIA3, the following steps would be taken: 1. Validating the message's integrity using the shared secret with DIA1, and removing the authenticated security AVPs. 2. Decrypting any encrypted AVPs using the secret shared with DIA1. 3. Re-encrypting AVPs using the secret shared with DIA3. Calhoun et al. expires March 2001 [Page 33] INTERNET DRAFT September 2000 4. Computing the message hash using the secret shared with DIA3, and adding it to the ICV AVP in the DIAMETER message. (Shared-Secret-1) (Shared-Secret-2) +------+ -----> +------+ ------> +------+ | | |1 3| | | | DIA1 +------------------>+ DIA2 +------------------>+ DIA3 | | | |2 4| | | +------+ +------+ +------+ Figure 6: Hop-by-Hop Security in Proxy Environments The above steps that each proxy MUST perform in a proxy chain clearly describes the security issues associated with hop-by-hop security in a proxy environment. Since the message integrity is re-computed at each node in the chain, it is not possible to detect if a proxy modified information in the message (e.g. session time). Furthermore, any sensitive information would be known to all proxies in the chain, since each node must decrypt AVPs. Therefore, Any AVPs that contain data that MUST NOT be seen by intermediate DIAMETER nodes MUST be protected via the mechanism described in the strong security extension [11]. It is highly recommended that the size of the shared secrets used be sufficiently long (e.g. 128 bits), and that different shared secrets be used for both authentication and encryption. 7.1.1 Integrity-Check-Value AVP The Integrity-Check-Value AVP (AVP Code 259) is of type complex and is used for hop-by-hop message authentication and integrity. The DIAMETER header as well as all AVPs (including padding) up to this AVP is protected by the Integrity-Check-Value. Note that the Message Length field in the DIAMETER header MUST be set to zero (0) prior to the ICV calculation. The Timestamp and Nonce AVPs MUST be present in the message PRIOR to the Integrity-Check-Value AVP. The Timestamp AVP provides replay protection and the Nonce AVP provides randomness. Any AVPs in a message that is not succeeded by the Integrity-Check-Value AVP MUST be ignored. The following is an example of a message that include hop-by-hop security: Calhoun et al. expires March 2001 [Page 34] INTERNET DRAFT September 2000 ::= [] All DIAMETER implementations SHOULD support this AVP. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ AVP Header (AVP Code = 259) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transform ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Key ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+-+-+-+-+ AVP Length The length of this attribute MUST be at least 13. Transform ID The Transform ID field contains a value that identifies the transform that was used to compute the ICV. The following values are defined in this document: HMAC-MD5-96[6] 1 The ICV is computed using the HMAC-MD5 algorithm, and the first 12 bytes of the hash output is included in the data portion of the ICV AVP. All DIAMETER implementations supporting this AVP MUST support this transform. Using the example code provided in [6], the following call would be used to generate the Integrity-Check-Value: hmac_md5(DiameterMessage, MessageLength, Secret, Secretlength, Output) Key ID The Key ID field contains a key identifier, which is used to identify the keying information used to generate the AVP's data field. Data The data field contains the output from the hashing algorithm. Calhoun et al. expires March 2001 [Page 35] INTERNET DRAFT September 2000 7.1.2 Encrypted-Payload AVP The Encrypted-Payload AVP (AVP Code 260) is of type complex and is used to encapsulate encrypted AVPs for privacy during transmission. Hop-by-Hop confidentiality is achieved by encapsulating all AVPs which are to be encrypted into an Encrypted-Payload AVP. This feature SHOULD be supported by DIAMETER implementations. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ AVP Header (AVP Code = 260) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transform ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Key ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Decrypted Data Length | Data ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ AVP Length The length of this attribute MUST be at least 13. Transform ID The Transform ID field contains a value that identifies the transform that was used to compute the ICV. The following values are defined in this document: MD5 1 See section 7.1.2.1 for more information. Key ID The Key ID field contains a key identifier, which is used to identify the keying information used to generate the AVP's data field. Decrypted Data Length The encrypted data length field contains the actual length of the decrypted data. This field is necessary in order to not treat the padded data as part of the plaintext. Data The data field contains the encrypted payload. 7.1.2.1 MD5 Payload Hiding Calhoun et al. expires March 2001 [Page 36] INTERNET DRAFT September 2000 MD5 Payload Hiding is supported by DIAMETER for backward compatibility with existing RADIUS infrastructure. The plain text (which is a buffer containing one or more AVPs) is first padded to a sixteen (16) byte boundary with 0 bytes. Since the encapsulated AVPs have length fields, it is possible to detect their boundaries, whether or not padding has been done. One or more Nonce AVPs MUST precede an Encrypted-Payload AVP. An MD5 hash is performed on the: - last Nonce AVP which precedes the Encrypted-Payload AVP - the shared authentication secret This MD5 hash value is then XORed with the first 16 octet segment of the buffer to encrypt. The resulting 16 octet result is saved as the first 16 octets of the encrypted buffer. The result is also used to calculate a new value using MD5: - the shared authentication secret - the 16 byte result of the previous XOR This value is then XORed with the next 16 bytes. This is done for each 16 bytes successively in the buffer to encrypt, producing an equal sized encrypted buffer. The receiver of a DIAMETER message with an Encrypted-Payload AVP MUST first check the integrity of the message, either through the ICV, or the CMS-Data AVP [11] if it protects the Encrypted-Payload AVP. Then the Encrypted-Payload AVP is decrypted, by reversing the above procedure, which applied to the buffer will reproduce the plain text version. The decapsulated AVPs are then used to process the DIAMETER message in the normal manner. 7.2 Nonce AVP The Nonce AVP (AVP Code 261) is of type Data and MUST be present prior to the Integrity-Check-Value AVPs within a message and is used to ensure randomness within a message. The content of this AVP MUST be a random value of at least 128 bits. Some crypto algorithms are known to have weaknesses if a random value is not found early within the plaintext, therefore it is recommended that the Nonce AVP be added early in a message if possible. 7.3 Timestamp AVP Calhoun et al. expires March 2001 [Page 37] INTERNET DRAFT September 2000 The Timestamp AVP (AVP Code 262) is of type Time and is used to add replay protection to the DIAMETER protocol. This AVP MUST appear prior to the Integrity-Check-Value AVP or any other message integrity AVP defined in separate extensions. The value of this AVP is the most significant four octets returned from an NTP [18] server that indicates the number of seconds expired since Jan. 1, 1900. Messages that are older than a configurable maximum age SHOULD be rejected (see section 10.0) and a response SHOULD be returned with the Result-Code AVP value set to DIAMETER_TIMEOUT. Note that the larger the configurable value, the more susceptible one is to a replay attack. However, one does have to take into account the possibility for clock drift, and the latency involved in the transmission of the message over the network. The timestamp AVP SHOULD be updated prior to retransmission. A DIAMETER node that receives a message with the Result-Code AVP set to DIAMETER-TIMEOUT MAY use the time found in the Timestamp AVP within the reply in order to synchronize its clock with its peer. When time synchronization is done, the sender MUST NOT change its local time, but SHOULD adjust the time delta for all outgoing messages to the peer, and require that its local time be used in received messages. Implementations must be prepared to wrap at the epochal 2038 where Time values are used, and 0,1,... MUST be considered greater than 2^32-1 at that time. 8.0 IANA Considerations This document defines a number of assigned numbers to be maintained by the IANA. This section explains the criteria to be used by the IANA to assign additional numbers in each of these lists. The following subsections describe the assignment policy for the namespaces defined elsewhere in this document. 8.1 AVP Attributes As defined in section 2.2, AVPs contain vendor ID, attribute and value fields. For vendor ID value of 0, IANA will maintain a registry of assigned AVP codes and in some case also values. Attribute 0-254 are assigned from the RADIUS protocol [1], whose attributes are also maintained through IANA. AVP Codes 256-280 are assigned within this document. The remaining values are available for assignment through Designated Expert [12]. Calhoun et al. expires March 2001 [Page 38] INTERNET DRAFT September 2000 8.2 Command Code Values As defined in section 2.1, the Command Code field has an associated value maintained by IANA. Values 0-255 are reserved for backward RADIUS compatibility, and values 256-258 are defined in this specification. The remaining values are available for assignment via Designated Expert [12]. 8.3 Extension Identifier Values As defined in section 2.6.5, the Extension Identifier is used to identify a specific DIAMETER Extension. All values, other than zero (0) are available for assignment via Standards Action [12]. Note that the DIAMETER protocol is not inteded to be extended for any purpose. Any extensions added to the protocol MUST ensure that they fit within the existing framework, and that no changes to the base protocol are required. 8.4 Result-Code AVP Values As defined in Section 5.2, the Result Code AVP (AVP Code 268) defines the values 0-8. All remaining values are available for assignment via IETF Consensus [12]. 8.5 Integrity-Check-Value AVP Transform Values Section 7.1.1 defines the Integrity-Check-Value AVP (AVP Code 259) which contains a field called the Transform. This document reserves the value 1. All remaining values are available for assignment via Designated Expert [12]. 8.6 AVP Header Bits There are six remaining reserved bits in the AVP header. Additional bits should only be assigned via a Standards Action [12]. 9.0 Open Issues The following are the open issues that SHOULD be addressed in future versions of the DIAMETER protocol: - AVPs of type 'Time" are 32 bits in size and contain the a Calhoun et al. expires March 2001 [Page 39] INTERNET DRAFT September 2000 timestamp consistent with NTP [18]. This field is expected to expire sometime in 2038. Future investigation SHOULD be done to determine if a 64 bit time format could be used. - The fact that the Sender's IP Address is used in the construction of the Session-Id means that the introduction of Network Address Translation MAY cause two hosts to represent the same Session Identifier. This area needs to be investigated further to be able to support DIAMETER hosts on a private network. - When additional hashing transforms are supporting by the DIAMETER base protocol, there SHOULD be a method to negotiate the transform to be used. This negotiation MUST NOT be prone to a bidding down attack to the lowest secure transform. - This specification defines the use of SCTP port 1812. This port has not been assigned to the DIAMETER protocol, and cannot be requested until SCTP becomes an RFC. 10.0 DIAMETER protocol related configurable parameters This section contains the configurable parameters that are found throughout this document: DIAMETER Peer A DIAMETER entity MAY communicate with peers that are statically configured. A statically configured DIAMETER peer would require that either the IP address or the fully qualified domain name (FQDN) be supplied, which would then be used to resolve through DNS. Realm Routing Table A DIAMETER Proxy server routes messages based on the realm portion of a Network Access Identifier (NAI). The server MUST have a table of Realms Names, and the address of the peer to which the message must be forwarded to. The routing table MAY also include a "default route", which is typically used for all messages that cannot be locally processed. Maximum Age of an outstanding message Messages older than the maximum age SHOULD be rejected, as described in section 7.3. The recommended value is 4 seconds. Shared Secret The shared secret is a value that is known by two communicating peers, and is used to generate the Integrity-Check-Value AVP. Calhoun et al. expires March 2001 [Page 40] INTERNET DRAFT September 2000 There is no default. 11.0 Security Considerations The DIAMETER base protocol requires that two communicating peers exchange messages in a secure fashion. This document describes two security methods that can be used. The first requires no security at the application layer, but rather relies on an underlying security mechanism, such as IP Security. When IP Security is not available, or desirable, the DIAMETER protocol MAY use hop-by-hop security, which requires communicating peers to share a long-lived secret. Hop-by-Hop security provides replay protection by requiring that the communicating peers share a time source, such as an NTP server. Information of a sensitive nature, which MUST NOT be seen by any intermediate DIAMETER node MUST NOT be encrypted using hop-by-hop encryption. When the DIAMETER protocol is used in an inter-domain network, strong application level security MAY be required, such as non-repudiation. When the communicating peers do require this level of security either for legal or business purposes, the extension defined in [11] MAY be used. This security model provides AVP-level authentication, and the encryption mechanism is designed such that only the target host has the keying information required to decrypt the information. 12.0 References [1] Rigney, et alia, "RADIUS", RFC-2138, April 1997 [2] Reynolds, Postel, "Assigned Numbers", RFC 1700, October 1994. [3] Postel, "User Datagram Protocol", RFC 768, August 1980. [4] Rivest, "The MD5 Message-Digest Algorithm", RFC 1321, April 1992. [5] Kaufman, Perlman, Speciner, "Network Security: Private Communi- cations in a Public World", Prentice Hall, March 1995, ISBN 0- 13-061466-1. [6] Krawczyk, Bellare, Canetti, "HMAC: Keyed-Hashing for Message Authentication", RFC 2104, January 1997. [7] P. Calhoun, W. Bulley, A. Rubens, J. Haag, "DIAMETER NASREQ Calhoun et al. expires March 2001 [Page 41] INTERNET DRAFT September 2000 Extension", draft-calhoun-diameter-nasreq-05.txt, IETF work in progress, September 2000. [8] Aboba, Beadles "The Network Access Identifier." RFC 2486. Janu- ary 1999. [9] Calhoun, Zorn, Pan, Akhtar, "DIAMETER Framework", draft- calhoun-diameter-framework-08.txt, IETF work in progress, June 2000. [10] P. Calhoun, C. Perkins, "DIAMETER Mobile IP Extensions", draft- calhoun-diameter-mobileip-11.txt, IETF work in progress, Sep- tember 2000. [11] P. Calhoun, W. Bulley, S. Farrell, "DIAMETER Strong Security Extension", draft-calhoun-diameter-strong-crypto-05.txt (work in progress), September 2000. [12] Narten, Alvestrand,"Guidelines for Writing an IANA Considera- tions Section in RFCs", BCP 26, RFC 2434, October 1998 [13] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [14] Myers, Ankney, Malpani, Galperin, Adams, "X.509 Internet Public Key Infrastructure Online Certificate Status Protocol (OCSP)", RFC 2560, June 1999. [15] Arkko, Calhoun, Patel, Zorn, "DIAMETER Accounting Extension", draft-calhoun-diameter-accounting-08.txt, IETF work in progress, September 2000. [16] Hinden, Deering, "IP Version 6 Addressing Architecture", RFC 2373, July 1998. [17] ISI, "Internet Protocol", RFC 791, September 1981. [18] Mills, "Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI, RFC 2030, October 1996. [19] Housley, Ford, Polk, Solo, "Internet X.509 Public Key Infras- tructure Certificate and CRL Profile", RFC 2459, January 1999. [20] B. Aboba, G. Zorn, "Criteria for Evaluating Roaming Protocols", RFC 2477, January 1999. [21] M. Beadles, D. Mitton, "Criteria for Evaluating Network Access Server Protocols", draft-ietf-nasreq-criteria-05.txt, IETF work Calhoun et al. expires March 2001 [Page 42] INTERNET DRAFT September 2000 in progress, June 2000. [22] T. Hiller and al, "CDMA2000 Wireless Data Requirements for AAA", draft-hiller-cdma2000-aaa-02.txt, IETF work in progress, Sep- tember 2000. [23] S. Glass, S. Jacobs, C. Perkins, "Mobile IP Authentication, Authorization, and Accounting Requirements", draft-ietf- mobileip-aaa-reqs-04.txt, IETF work in progress, June 2000. [24] F. Yergeau, "UTF-8, a transformation format of ISO 10646", RFC 2279, January 1998. [25] P. Calhoun, A. Rubens, H. Akhtar, E. Guttman, W. Bulley, J. Haag, "DIAMETER Implementation Guidelines", draft-calhoun- diameter-impl-guide-03.txt, IETF work in progress, June 2000. [26] R. Stewart et al., "Simple Control Transmission Protocol", draft-ietf-sigtran-sctp-13.txt, IETF Work in Progress, July 2000. [27] Postel, J. "Transmission Control Protocol", RFC 793, January 1981. [28] E. Guttman, C. Perkins, J. Veizades, M. Day. "Service Location Protocol, Version 2", RFC 2165, June 1999. [29] P. Calhoun, N. Greene, "DIAMETER Resource Management", draft- calhoun-diameter-res-mgmt-05.txt, IETF Work in Progress, Sep- tember 2000. 13.0 Acknowledgements The authors would like to thank Nenad Trifunovic, Tony Johansson and Pankaj Patel for their participation in the Document Reading Party. The authors would also like to acknowledge the following people for their contribution in the development of the DIAMETER protocol: Bernard Aboba, Jari Arkko, William Bulley, Daniel C. Fox, Lol Grant, Ignacio Goyret, Nancy Greene, Peter Heitman, Paul Krumviede, Fergal Ladley, Ryan Moats, Victor Muslin, Kenneth Peirce, Stephen Farrell, Sumit Vakil, John R. Vollbrecht, Jeff Weisberg, Jon Wood and Glen Zorn 14.0 Authors' Addresses Calhoun et al. expires March 2001 [Page 43] INTERNET DRAFT September 2000 Questions about this memo can be directed to: Pat R. Calhoun Network and Security Research Center, Sun Laboratories Sun Microsystems, Inc. 15 Network Circle Menlo Park, California, 94025 USA Phone: +1 650-786-7733 Fax: +1 650-786-6445 E-mail: pcalhoun@eng.sun.com Allan C. Rubens Tut Systems, Inc. 220 E. Huron, Suite 260 Ann Arbor, MI 48104 USA Phone: +1 734-995-1697 E-Mail: arubens@tutsys.com Haseeb Akhtar Wireless Technology Labs Nortel Networks 2221 Lakeside Blvd. Richardson, TX 75082-4399 USA Phone: +1 972-684-8850 E-Mail: haseeb@nortelnetworks.com Erik Guttman Network and Security Research Center, Sun Laboratories Sun Microsystems, Inc. Eichhoelzelstr. 7 74915 Waibstadt Germany Phone: +49-7263-911-701 E-mail: erik.guttman@germany.sun.com 15.0 Full Copyright Statement Calhoun et al. expires March 2001 [Page 44] INTERNET DRAFT September 2000 Copyright (C) The Internet Society (1999). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this docu- ment itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of develop- ing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The lim- ited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DIS- CLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Calhoun et al. expires March 2001 [Page 45]