INTERNET DRAFT Pat R. Calhoun
Category: Informational Erik Guttman
Title: draft-calhoun-diameter-impl-guide-00.txt Sun Microsystems, Inc.
Date: December 1999 Allan C. Rubens
Tut Systems, Inc.
Haseeb Akhtar
Nortel Networks
William Bulley
Merit Network, Inc.
Jeff Haag
Cisco Systems
DIAMETER Implementation Guidelines
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@ipass.com mailing list.
Distribution of this memo is unlimited.
Copyright (C) The Internet Society 1999. All Rights Reserved.
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Abstract
The DIAMETER protocol is used for Authentication, Authorization and
Accounting (AAA) for Mobile-IP and NASREQ. This document contains
implementation guidelines that may be useful to DIAMETER protocol
developers.
Table of Contents
1.0 Introduction
2.0 Base Protocol
2.1 Acknowledgment Timeouts
2.1.1 Calculating Adaptive Acknowledgment Timeout
2.1.2 Flow Control: Adjusting for Timeout
2.2 Examples of sequence numbering
2.2.1 Lock-step tunnel establishment
2.2.2 Multiple messages acknowledged
2.2.3 Lost message with retransmission
2.3 Backward Compatibility with RADIUS
2.4 Delayed Acknowledgement Optimization
2.5 Device-Reboot-Ind Message Flow
2.6 Device-Watchdog-Ind Message Flow
2.7 Message-Reject-Ind Message Flow
2.8 Peer Fail-Over and Load Balancing
3.0 NASREQ Extension
3.1 EAP Retransmission and Timer
3.2 Example of an EAP OTP Authentication
3.2.1 Successful Authentication
3.2.2 NAS Initiated EAP Authentication
3.2.3 Server-Initiated Authentication
3.2.4 Example of failed EAP Authentication
3.2.5 Example of DIAMETER Server not supporting EAP
3.2.6 Example of DIAMETER Proxy not supporting EAP
3.2.7 Example of PPP Client not supporting EAP
4.0 References
5.0 Acknowledgements
5.0 Author's Addresses
6.0 Full Copyright Statement
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1.0 Introduction
The DIAMETER protocol is used for Authentication, Authorization and
Accounting (AAA) for Mobile-IP and NASREQ. This document contains
implementation guidelines that may be useful to DIAMETER protocol
developers.
This specification contains implementation guidelines for both the
DIAMETER base protocol [2] and the NASREQ extension [3].
2.0 Base Protocol
This section contains implementation guidelines for the DIAMETER Base
protocol [2].
2.1 Acknowledgment Timeouts
DIAMETER uses sliding windows and timeouts to provide flow-control
across the underlying medium and to perform efficient data buffering
to keep two DIAMETER peers' receive window full without causing
receive buffer overflow. DIAMETER requires that a timeout be used to
recover from dropped messages.
When the timeout for a peer expires, the previously transmitted
message with Ns value equal to the highest in-sequence value of Nr
received from the peer is retransmitted. The receiving peer does not
advance its value for the receive sequence number state, Sr, until it
receives a message with Ns equal to its current value of Sr.
This rule assures that all subsequent acknowledgements to this peer
will contain an Nr value equal to the Ns value of the first missing
message until a message with the missing Ns value is received.
The exact implementation of the acknowledgment timeout is vendor-
specific. It is suggested that an adaptive timeout be implemented
with back-off for flow control. The timeout mechanism proposed here
has the following properties:
Independent timeouts for each peer. A device will have to
maintain and calculate timeouts for every active peer.
An administrator-adjustable maximum timeout, MaxTimeOut, unique to
each device.
An adaptive timeout mechanism that compensates for changing
throughput. To reduce message processing overhead, vendors may
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choose not to recompute the adaptive timeout for every received
acknowledgment. The result of this overhead reduction is that the
timeout will not respond as quickly to rapid network changes.
Timer back-off on timeout to reduce congestion. The backed-off
timer value is limited by the configurable maximum timeout value.
Timer back-off is done every time an acknowledgment timeout
occurs.
In general, this mechanism has the desirable behavior of quickly
backing off upon a timeout and of slowly decreasing the timeout value
as messages are delivered without errors.
2.1.1 Calculating Adaptive Acknowledgment Timeout
We must decide how much time to allow for acknowledgments to return.
If the timeout is set too high, we may wait an unnecessarily long
time for dropped messages. If the timeout is too short, we may time
out just before the acknowledgment arrives. The acknowledgment
timeout should also be reasonable and responsive to changing network
conditions.
The suggested adaptive algorithm detailed below is based on the TCP
1989 implementation and is explained in Richard Steven's book TCP/IP
Illustrated, Volume 1 (page 300). 'n' means this iteration of the
calculation, and 'n-1' refers to values from the last calculation.
DIFF[n] = SAMPLE[n] - RTT[n-1]
DEV[n] = DEV[n-1] + (beta * (|DIFF[n]| - DEV[n-1]))
RTT[n] = RTT[n-1] + (alpha * DIFF[n])
ATO[n] = MIN (RTT[n] + (chi * DEV[n]), MaxTimeOut)
DIFF represents the error between the last estimated round-trip time
and the measured time. DIFF is calculated on each iteration.
DEV is the estimated mean deviation. This approximates the standard
deviation. DEV is calculated on each iteration and stored for use in
the next iteration. Initially, it is set to 0.
RTT is the estimated round-trip time of an average message. RTT is
calculated on each iteration and stored for use in the next
iteration. Initially, it is set to PPD.
ATO is the adaptive timeout for the next transmitted message. ATO is
calculated on each iteration. Its value is limited, by the MIN
function, to be a maximum of the configure MaxTimeOut value.
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Alpha is the gain for the round trip estimate error and is typically
1/8 (0.125).
Beta is the gain for the deviation and is typically 1/4 (0.250).
Chi is the gain for the timeout and is typically set to 4.
To eliminate division operations for fractional gain elements, the
entire set of equations can be scaled. With the suggested gain
constants, they should be scaled by 8 to eliminate all division. To
simplify calculations, all gain values are kept to powers of two so
that shift operations can be used in place of multiplication or
division. The above calculations are carried out each time an
acknowledgment is received for a message that was not retransmitted
(no timeout occurred).
2.1.2 Flow Control: Adjusting for Timeout
This section describes how the calculation of ATO is modified in the
case where a timeout does occur. When a timeout occurs, the timeout
value should be adjusted rapidly upward. To compensate for shifting
internetwork time delays, a strategy must be employed to increase the
timeout when it expires. A simple formula called Karn's Algorithm is
used in TCP implementations and may be used in implementing the
back-off timers for the DIAMETER peers. Notice that in addition to
increasing the timeout, we also shrink the size of the window as
described in the next section.
Karn's timer back-off algorithm, as used in TCP, is:
NewTIMEOUT = delta * TIMEOUT
Adapted to our timeout calculations, for an interval in which a
timeout occurs, the new timeout interval ATO is calculated as:
RTT[n] = delta * RTT[n-1]
DEV[n] = DEV[n-1]
ATO[n] = MIN (RTT[n] + (chi * DEV[n]), MaxTimeOut)
In this modified calculation of ATO, only the two values that
contribute to ATO and that are stored for the next iteration are
calculated. RTT is scaled by delta, and DEV is unmodified. DIFF is
not carried forward and is not used in this scenario. A value of 2
for Delta, the timeout gain factor for RTT, is suggested.
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2.2 Examples of sequence numbering
This appendix uses several common scenarios to illustrate how
sequence number state progresses and is interpreted.
2.2.1 Lock-step session establishment
In this example, a DIAMETER host establishes communication with a
peer, with the exchange involving each side alternating in the
sending of messages. This example is contrived, in that the final
acknowledgement typically would be included in the Device-Watchdog-
Ind message.
DIAMETER Host A DIAMETER Host B
-> Device-Reboot-Ind
Nr: 0, Ns: 0
(ZLB) <-
Nr: 1, Ns: 0
-> Device-Watchdog-Ind
Nr: 0, Ns: 1
(delay)
(ZLB) <-
Nr: 2, Ns: 0
2.2.2 Multiple messages acknowledged
This example shows a flow of messages from DIAMETER Host B to Host A,
with Host A having no traffic of its own. Host A is waiting 1/4 of
its timeout interval, and then acknowledging all messages seen since
the last interval.
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DIAMETER Host A DIAMETER Host B
(previous message flow precedes this)
-> (ZLB)
Nr: 7000, Ns: 1000
(non-ZLB) <-
Nr: 1000, Ns: 7000
(non-ZLB) <-
Nr: 1000, Ns: 7001
(non-ZLB) <-
Nr: 1000, Ns: 7002
(Host A's timer indicates it should acknowledge pending
traffic)
-> (ZLB)
Nr: 7003, Ns: 1000
2.2.3 Lost message with retransmission
Host A attempts to communicate with Host B. The Device-Reboot-Ind
sent from B to A is lost and must be retransmitted by Host B.
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DIAMETER Host A DIAMETER Host B
-> Device-Reboot-Ind
Nr: 0, Ns: 0
(message lost) Device-Reboot-Ind <-
Nr: 1, Ns: 0
(pause; Host A's timer started first, so fires first)
-> Device-Reboot-Ind
Nr: 0, Ns: 0
(Host B realizes it has already seen this message)
(Host B might use this as a cue to retransmit, as in this
example)
Device-Reboot-Ind <-
Nr: 1, Ns: 0
-> Device-Watchdog-Ind
Nr: 1, Ns: 1
(delay)
(ZLB) <-
Nr: 2, Ns: 1
2.3 Backward Compatibility with RADIUS
The DIAMETER protocol was designed with RADIUS [1] compatibility in
mind. A DIAMETER node MAY listen for incoming RADIUS and DIAMETER
packets on the same UDP port. The first octet in the message would
indicate whether the message is of type RADIUS or DIAMETER.
The RADIUS protocol defines a one octet attribute space, and the
DIAMETER protocol reserves the first 255 attribute identifiers to be
the same as those defined in RADIUS. This allows DIAMETER servers to
easily perform protocol conversion, since an additional dictionary
lookup would not be necessary in order to map a RADIUS attribute to a
DIAMETER AVP.
By re-using the RADIUS attribute space, a DIAMETER server could
easily read a typical RADIUS user profile without any additional
conversions. This reduces the need to create duplicate user profiles
for both protocols, and also does not require any database conversion
while reading the profiles.
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2.4 Delayed Acknowledgement Optimization
This optimization will potentially reduce the amount of traffic sent
between DIAMETER peers. This optimization affects when
acknowledgments are sent, as presented in Section 3.1 of [2].
If a peer does not have a message queued to transmit at the time a
non-ZLB message is received then it should delay a short time before
sending a ZLB message containing the latest values of Sr and Ss, as
described above. This short delay is to allow for the possible
arrival of a message to be transmitted back to its peer, thus
avoiding the need to issue a ZLB. The suggested value for this time
delay is 1/4 the receiving peer's value of Round-Trip-Time (RTT - see
Appendix A), if it computes RTT, or a maximum of 1/2 of its fixed
acknowledgment timeout interval otherwise. This timeout should
provide a reasonable opportunity for the receiving peer to obtain a
payload message destined for its peer, upon which the ACK of the
received message MAY be piggybacked. Note that if a peer's window is
full, it MAY advertise an older Nr value if it is not ready to accept
new messages.
This delay value should be treated as a suggested maximum; an
implementation could make this delay quite small without adversely
affecting the protocol. The default time delay is 2 seconds. To
provide for better throughput, the receiving peer should skip this
delay entirely and send a ZLB message immediately in the case where
its receive window is filled and it has no queued data to send for
this connection or it can't send queued data because the transmit
window is closed.
2.5 Device-Reboot-Ind Message Flow
The following figure depicts a sample flow of Device-Reboot-Ind
between three DIAMETER peers, one being a proxy or broker server. In
this example DIA1 initiates the bootstrap sequence with DIA2, and
later DIA3 initiates the bootstrap sequence with DIA2. After some
time DIA1 needs to reboot and informs DIA2. The details of each
message is provided below.
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+-------+ +-------+ +-------+
| DIA1 | | PROXY | | DIA3 |
| | | DIA2 | | |
+-------+ +-------+ +-------+
| | |
|DRI (ns=0, nr=0) | |
| Rebooted | |
| version 1, | |
| extensions 1, 4 | |
(a) |------------------->| |
|DRI (ns=0, nr=1) | |
| Rebooted | |
| version 1, | |
| extension 1 | |
(b) |<-------------------| |
|ZLB (ns=0, nr=1) | |
(c) |------------------->| |
| . |DRI (ns=0, nr=0) |
| . | Rebooted |
| | version 1, |
| | extensions 1, 2 |
(d) | |<------------------|
| |DRI (ns=0, nr=1) |
| | Rebooted |
| | version 1, |
| | extension 1 |
(e) | |------------------>|
| |ZLB (ns=0, nr=1) |
(f) | |<------------------|
|DRI (ns=x, nr=y) | . |
| Upcoming Reboot | . |
(g) |------------------->| |
| . | |
| . | |
|DRI (ns=0, nr=0) | |
| Rebooted | |
| version 1, | |
| extensions 1, 4 | |
(h) |------------------->| |
| | |
Figure 1: Sample DRI Message Flow in a Proxy Environment
(a) DIA1 sends a DRI message to DIA2 indicating that its version
is one (1) and that its supported extensions are 1 (Roamops)
and 4 (Mobile-IP).
(b) DIA2 sends a DRI message to DIA1 indicating that its version
is one (1) and that its supported extension is 1 (Roamops).
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This message also includes a piggy-backed acknowledgement of
(a).
(c) DIA1 sends an acknowledgement of (b)
(d) DIA3 sends a DRI message to DIA2 indicating that its version
is one (1) and that its supported extensions are 1 (Roamops)
and 2 (Secure Proxy).
(e) DIA2 sends a DRI message to DIA3 indicating that its version
is one (1) and that its supported extension is 1 (Roamops).
This message also includes a piggy-backed acknowledgement of
(d).
(f) DIA3 sends an acknowledgement of (e)
(g) after some time DIA1 sends an indication to DIA2 that it is
about to reboot. All messages destined to the domain for which
DIA1 is responsible for should be redirected to an alternate
DIAMETER Server.
(h) Once the reboot is complete, DIA sends the DRI, which causes
steps (a) through (c) to be repeated.
2.6 Device-Watchdog-Ind Message Flow
The following figure provides an example of how the Device-Watchdog-
Ind message is used in a proxy environment. The details of each
message is provided below.
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+-------+ +-------+ +-------+
| DIA1 | | PROXY | | DIA3 |
| | | DIA2 | | |
+-------+ +-------+ +-------+
| | |
|CMD-X (ns=23, nr=40)| |
(a) |------------------->| |
|ZLB (ns=40, nr=24) | |
(b) |<-------------------| |
| . | |
| . | |
| |CMD-Y (ns=12, nr=20)|
(c) | |------------------->|
| |ZLB (ns=20, nr=13) |
(d) | |<-------------------|
|WDI (ns=24, nr=40) | . |
(e) |------------------->| . |
|ZLB (ns=40, nr=25) | |
(f) |<-------------------| |
| |WDI (ns=21, nr=13) |
(g) | |<-------------------|
| |ZLB (ns=13, nr=22) |
(h) | |------------------->|
| | |
Figure 2: Sample WDI Message in a Proxy Environment
(a) DIA1 issues a message to DIA2
(b) DIA2 acknowledges the receipt of (a)
(c) DIA2 issues a message to DIA3
(d) DIA3 acknowledges the receipt of (c)
(e) After some time of inactivity, DIA1 issues a WDI to DIA2
(f) DIA2 acknowledges the receipt of (e)
(g) After some period of inactivity, DIA3 issues a WDI to DIA2
(h) DIA2 acknowledges the receipt of (g)
2.7 Message-Reject-Ind Message Flow
The following figure show sample flows of MRI command between two
DIAMETER peers. In this example DIA1 and DIA2 servers generates error
messages. The details of the messages are provided below.
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+-------+ +-------+
| DIA1 | | DIA2 |
+-------+ +-------+
| |
|Unknown command |
(a) |------------------------------------>|
|MRI, err=DIAMETER_COMMAND_UNSUPPORTED|
(b) |<------------------------------------|
| . |
| . |
|Unknown AVP |
(c) |<------------------------------------|
|MRI, err=DIAMETER_AVP_UNSUPPORTED |
(d) |------------------------------------>|
| . |
| . |
|Bad value in a valid AVP |
(e) |------------------------------------>|
|MRI, err=DIAMETER_INVALID_AVP_VALUE |
(f) |<------------------------------------|
Figure 3: Sample MRI Message Flow
(a) DIA2 receives an unknown command from DIA1.
(b) DIA2 recognizes that it received an unknown command and hence
sends an MRI with the Result-Code AVP set to
DIAMETER_COMMAND_UNSUPPORTED and the Command-Code AVP
encapsulated within the Failed-AVP AVP.
(c) DIA1 receives an unknown AVP in a message sent by DIA2.
(d) DIA1 recognizes that it received an unknown AVP and returns an
MRI with the Result-Code AVP set to DIAMETER_AVP_UNSUPPORTED
and the offending AVP encapsulated within a Failed-AVP AVP.
(e) DIA2 receives a bad parameter within a otherwise valid AVP
from DIA1.
(f) As soon as it discovers that it has received a bad parameter,
it returns an MRI message to DIA1 with the Result-Code AVP set
to DIAMETER_INVALID_AVP_VALUE and the offending AVP
encapsulated within a Failed-AVP AVP.
2.8 Peer Fail-Over and Load Balancing
Although not a function of the DIAMETER protocol, in some networks it
is desirable to ensure resilient service by providing alternate
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peers, should communication with a peer fail. Figure 4 provides an
example of such a network, where the client communicates with one of
two servers providing proxying services. The proxy servers, in turn,
communicate with one of two servers in the home domain.
+--------+
| DIAM |
| Primary|
+--------+ | Home |
| DIAM +---------+ Server +----+
| Primary| +--------+ |
+--------+ | Proxy | +--------+ |
| +--------+ Server +---------+ DIAM | |
| DIAM | +--------+ |Alternat| |
| Client | +--------+ | Home | |
| +--------+ DIAM +---------+ Server | |
+--------+ |Alternat| +--------+ |
| Proxy | |
| Server +-----------------------+
+--------+
Figure 4: Redundant DIAMETER Servers
Each node in the network MUST know a priori about its communicating
peers, and each peer MAY have a relative priority, forcing all
traffic to be sent through a preferred server, if it is available.
When a node detects that a communicating peer is no longer available,
it MUST attempt to redirect all traffic (including the packets in the
retransmission queue destined for the former peer) to the new peer.
It is possible that an alternate path not exist, such would be the
case if the DIAMETER Client was no longer reachable. In this case,
the DIAMETER proxy servers SHOULD drop all responses directed to the
client, and MUST respond to all requests directed to the client with
an appropriate Result Code.
An implementation MAY also make use of the multiple peer arrangement
described above to balance the load between a set of peers. A clever
implementation MAY also redirect traffic to an alternate peer when it
detects that its primary communicating peer's window is full.
3.0 NASREQ Extension
This section contains implementation guidelines for the NASREQ
DIAMETER Extension [3].
3.1 EAP Retransmission and Timers
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As noted in [4], the EAP authenticator (NAS) is responsible for
retransmission of packets between the authenticating peer and the
NAS. Thus if an EAP packet is lost in transit between the
authenticating peer and the NAS (or vice versa), the NAS will
retransmit. As defined in the base protocol [2], a DIAMETER node is
responsible to retransmit all packets with its peer.
Note that it may be necessary to adjust authentication timeouts in
certain cases. For example, when a token card is used additional time
may be required to allow the user to find the card and enter the
token. Since the NAS will typically not have knowledge of the
required parameters, these need to be provided by the DIAMETER
server. This can be accomplished by inclusion of the Idle-Timeout in
the DIAMETER-EAP-Answer message.
3.2 Example of an EAP OTP Authentication
This section provides sample messages exchanges between an
Authenticating Peer, which is typically a dial-up PPP client, a NAS
and a DIAMETER server. The protocol used between the Dial-up PPP
client and the NAS is EAP over PPP as defined in [4]. The protocol
between the NAS and the DIAMETER Server is EAP encapsulated within
DIAMETER, as described in this specification.
For all PPP packets, the messages are formatted as:
[LCP Packet Type]
[EAP Packet Type]/[EAP Payload]
For all DIAMETER packets, the messages are formatted as:
[DIAMETER Command Code]/[EAP Packet Type]/[EAP Payload]
In the example provided below, the PPP client attempts to
authenticate using a One-Time-Password [5] encapsulated within EAP
[4].
3.2.1 Successful Authentication
The example below shows the conversation between the authenticating
peer, NAS, and server, for the case of a One Time Password (OTP)
authentication. OTP is used only for illustrative purposes; other
authentication protocols could also have been used, although they
would show somewhat different behavior.
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Authenticating Peer NAS DIAMETER Server
------------------- --- ---------------
<- PPP LCP Request-EAP
auth
PPP LCP ACK-EAP
auth ->
DIAMETER-
EAP-Request/
EAP-Payload/Start ->
<- DIAMETER-
EAP-Answer/
EAP-
Payload/Identity
<- PPP EAP-Request/
Identity
PPP EAP-Response/
Identity (MyID) ->
DIAMETER-
EAP-Request/
EAP-Payload/
EAP-Response/
(MyID) ->
<- DIAMETER-
EAP-Answer/
EAP-Payload/EAP-
Request
OTP/OTP Challenge
<- PPP EAP-Request/
OTP/OTP Challenge
PPP EAP-Response/
OTP, OTPpw ->
DIAMETER-
EAP-Request/
EAP-Payload/
EAP-Response/
OTP, OTPpw ->
<- DIAMETER-
EAP-Answer/
EAP-Payload/EAP-
Success
(other AVPs)
<- PPP EAP-Success
PPP Authentication
Phase complete,
NCP Phase starts
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3.2.2: NAS Initiated EAP Authentication
In the case where the NAS sends the authenticating peer an EAP-
Request/Identity packet without first sending an EAP-Start packet to
the DIAMETER server, the conversation would appear as follows:
Authenticating Peer NAS DIAMETER Server
------------------- --- ---------------
<- PPP LCP Request-EAP
auth
PPP LCP ACK-EAP
auth ->
<- PPP EAP-Request/
Identity
PPP EAP-Response/
Identity (MyID) ->
DIAMETER-
EAP-Request/
EAP-Payload/
EAP-Response/
(MyID) ->
<- DIAMETER-
EAP-Answer/
EAP-Payload/EAP-Request
OTP/OTP Challenge
<- PPP EAP-Request/
OTP/OTP Challenge
PPP EAP-Response/
OTP, OTPpw ->
DIAMETER-
EAP-Request/
EAP-Payload/
EAP-Response/
OTP, OTPpw ->
<- DIAMETER-
EAP-Answer/
EAP-Payload/EAP-Success
(other AVPs)
<- PPP EAP-Success
PPP Authentication
Phase complete,
NCP Phase starts
3.2.3: Server-Initiated Authentication
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As described in [6], when a server has successfully authenticated and
authorized a user, it may include a timeout period to the
authorization. The server can later initiate an unsolicited re-
authentication request to the user, through the NAS. This method has
the advantage of reducing the number of round trips required for re-
authentication/authorization.
Authenticating Peer NAS DIAMETER Server
------------------- --- ---------------
<- DIAMETER-EAP-Ind/
EAP-Payload/EAP-Request
OTP/OTP Challenge
<- PPP EAP-Request/
OTP/OTP Challenge
PPP EAP-Response/
OTP, OTPpw ->
DIAMETER-
EAP-Request/
EAP-Payload/
EAP-Response/
OTP, OTPpw ->
<- DIAMETER-
EAP-Answer/
EAP-Payload/EAP-Success
(other AVPs)
<- PPP EAP-Success
3.2.4: Example of failed EAP Authentication
In the case where the client fails EAP authentication,
the conversation would appear as follows:
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Authenticating Peer NAS DIAMETER Server
------------------- --- ---------------
<- PPP LCP Request-EAP
auth
PPP LCP ACK-EAP
auth ->
DIAMETER-
EAP-Request/
EAP-Payload/Start ->
<- DIAMETER-
EAP-Answer/
EAP-Payload/Identity
<- PPP EAP-Request/
Identity
PPP EAP-Response/
Identity (MyID) ->
DIAMETER-
EAP-Request/
EAP-Payload/
EAP-Response/
(MyID) ->
<- DIAMETER-
EAP-Answer/
EAP-Payload/EAP-Request
OTP/OTP Challenge
<- PPP EAP-Request/
OTP/OTP Challenge
PPP EAP-Response/
OTP, OTPpw ->
DIAMETER-
EAP-Request/
EAP-Payload/
EAP-Response/
OTP, OTPpw ->
<- DIAMETER-
EAP-Answer/
EAP-Payload/EAP-Failure
<- PPP EAP-Failure
<- LCP Terminate
3.2.5: Example of DIAMETER Server not supporting EAP
In the case that the DIAMETER server or proxy does not support EAP
extensions the conversation would appear as follows:
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Authenticating Peer NAS DIAMETER Server
------------------- --- ---------------
<- PPP LCP Request-EAP
auth
PPP LCP ACK-EAP
auth ->
DIAMETER
EAP-Request/
EAP-Payload/Start ->
<- DIAMETER
Command-Unrecognized
<- PPP LCP Request-CHAP
auth
PPP LCP ACK-CHAP
auth ->
<- PPP CHAP Challenge
PPP CHAP Response ->
DIAMETER
AA-Request->
<- DIAMETER
AA-Answer
<- PPP LCP
CHAP-Success
PPP Authentication
Phase complete,
NCP Phase starts
3.2.6: Example of DIAMETER Proxy not supporting EAP
In the case where the local DIAMETER Server does support the EAP
extensions but the remote DIAMETER Server does not, the conversation
would appear as follows:
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Authenticating Peer NAS DIAMETER Server
------------------- --- ---------------
<- PPP LCP Request-EAP
auth
PPP LCP ACK-EAP
auth ->
DIAMETER-
EAP-Request/
EAP-Payload/Start ->
<- DIAMETER-
EAP-Answer/
EAP-Payload/Identity
<- PPP EAP-Request/
Identity
PPP EAP-Response/
Identity
(MyID) ->
DIAMETER-
EAP-Request/
EAP-Payload/EAP-Response/
(MyID) ->
<- DIAMETER-
EAP-Answer
(proxied from remote
DIAMETER Server)
<- PPP LCP Request-CHAP
auth
PPP LCP ACK-CHAP
auth ->
<- PPP CHAP Challenge
PPP CHAP Response ->
DIAMETER
AA-Request->
<- DIAMETER
AA-Answer
(proxied from remote
DIAMETER Server)
<- PPP LCP
CHAP-Success
PPP Authentication
Phase complete,
NCP Phase starts
3.2.7: Example of PPP Client not supporting EAP
In the case where the authenticating peer does not support EAP, but
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where EAP is required for that user, the conversation would appear as
follows:
Authenticating Peer NAS DIAMETER Server
------------------- --- ---------------
<- PPP LCP Request-EAP
auth
PPP LCP NAK-EAP
auth ->
<- PPP LCP Request-EAP
auth
PPP LCP NAK-EAP
auth ->
<- PPP LCP Request-CHAP
auth
PPP LCP ACK-CHAP
auth ->
<- PPP CHAP Challenge
PPP CHAP Response ->
DIAMETER-
AA-Request/
User-Name,
CHAP-Password ->
<- DIAMETER-
EAP-Answer/
EAP-Payload
<- LCP Terminate Req
4.0 References
[1] Rigney, et alia, "RADIUS", RFC-2138, April 1997
[2] P. Calhoun, A. Rubens, H. Akhtar, E. Guttman, "DIAMETER Base
Protocol", draft-calhoun-diameter-11.txt (work in progress),
December 1999.
[3] P. Calhoun, W. Bulley, A. Rubens, J. Haag, "DIAMETER NASREQ
Extension", draft-calhoun-diameter-nasreq-00.txt (work in
progress), December 1999.
[4] L. J. Blunk, J. R. Vollbrecht, "PPP Extensible Authentication
Protocol (EAP)." RFC 2284, March 1998.
[5] N Haller, C. Metz, P. Nesset, M. Straw, "A One-Time Password
(OTP) System", RFC 2289, February 1998.
[6] G. Zorn, P. Calhoun, "Limiting Fraud in Roaming", draft-ietf-
roamops-fraud-limit-00.txt (work in progress), May 1999.
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5.0 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, Sumit Vakil, John
R. Vollbrecht and Jeff Weisberg and Glen Zorn.
6.0 Author's Addresses
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
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E-Mail: haseeb@nortelnetworks.com
Erik Guttman
Network and Security Research Center, Sun Laboratories
Sun Microsystems, Inc.
15 Network Circle
Menlo Park, California, 94025
USA
Phone: 49-7263-911-701
E-mail: erik.guttman@germany.sun.com
William Bulley
Merit Network, Inc.
Building One, Suite 2000
4251 Plymouth Road
Ann Arbor, Michigan 48105-2785
USA
Phone: 1-734-764-9993
Fax: 1-734-647-3185
E-mail: web@merit.edu
Jeff Haag
Cisco Systems
7025 Kit Creek Road
PO Box 14987
Research Triangle Park, NC 27709
Phone: 1-919-392-2353
E-Mail: haag@cisco.com
7.0 Full Copyright Statement
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
Calhoun et al. expires May 2000 [Page 24]
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Internet Society or other Inter- net organizations, except as needed
for the purpose of developing 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 limited permis- sions 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
DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO ANY WAR- RANTY 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 May 2000 [Page 25]