Internet Engineering Task Force Tsunemasa Hayashi, NTT
Internet Draft Daisuke Andou, NTT
August, 2003 Haixiang He, Nortel Networks
Expires: February, 2004 Wassim Tawbi, Nortel Networks
Teruki Niki, Matsushita Electric Industrial
Internet Group membership Authentication Protocol (IGAP)
<draft-hayashi-igap-03.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 except that the right to
produce derivative works is not granted.
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Abstract
This memo documents the Internet Group membership Authentication
Protocol (IGAP), a protocol developed by NTT, Nortel Networks and
Panasonic. IGAP provides IGMP's group membership control between
hosts and their first-hop routers, with the addition of user
authentication and accounting. IGAP is designed to be used in a
controlled or managed IPv4 multicast environment, when authentication
and accounting are required. The user authentication information in
IGAP can enable a provider to control the distribution of the
multicast traffic as well as to collect real time user accounting
information in an environment where the last-hop access networks are
not shared.
1. Introduction
IP multicast provides an efficient mechanism for delivering packets
to multiple destinations. Unfortunately, IP multicast services,
especially commercial IP multicast services, are not widely deployed.
One of the important obstacles to its deployment is related to the
current IP multicast model. The current IP multicast model provides
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by nature a non-secure, non-controlled way for end systems attached
to a network to access multicast traffic. Lack of access control in
this model makes it difficult for a service provider to generate
enough revenue to sustain multicast services such as IP
multicast-based Internet TV.
A provider can enforce such access control through static
configuration on the last-hop network devices, including Ethernet
switches or routers. There are two major disadvantages to this
approach. First, static configuration does not fit into the
environment where the access control policy changes dynamically.
Second, the access control policy can only be based on physical
ports, hosts IP or MAC addresses, and hence it can not be used in an
environment where user based access control policy is required.
This leads to the need for a comprehensive way to authenticate and
authorize end systems before they are granted access to some
multicast groups. This need is met by the Internet Group membership
Authentication Protocol (IGAP).
IGAP allows last-hop network devices to enforce multicast receiver
access control in a non-shared access-control environment. IGAP
provides not only group membership control but also user
authentication and accounting. IGAP can be used when authentication
and accounting are required for multicast data access, while IGMP can
be used when they are not required. IGAP is used only in an IPv4
environment. IGAP enables an IP multicast service provider to
authenticate and authorize a host's requests to join a specific
multicast group based on its user's authentication information and
then to control the user's access to the multicast traffic
accordingly.
IGAP employs a user-based authentication model rather than an
authentication model based upon IP address or MAC address. The
benefits of a user-based model are well known: operational simplicity
and flexibility, in particular with respect to adds, moves, and
changes.
Another issue that discourages the wide deployment of IP multicast
services is the lack of multicast network management functions,
especially an effective multicast accounting function. Effective
user-based accounting information is critical in two aspects. On one
hand, network providers of commercial multicast services need to
accurately identify the users and collect their usage information to
generate correct billing information. On the other hand, some
content providers need to learn the content usage information. For
example, in IP multicast based Internet TV services, network
providers need to know which TV program is being watched and how long
a user watches so that they can charge the user based on the value of
the TV program. In addition, content providers and TV program owners
need to know the number of viewers of a TV program and how long they
watch the TV program in order to generate appropriate advertisement
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revenue.
IGAP combines user information, including user ID, with the multicast
group addresses that reflect the different contents. Authenticated
and authorized group join requests enable providers to effectively
collect the user usage information for different content.
IGAP not only encourages the wide deployment of new commercial IP
multicast services, but also can be used in non-commercial
environments such as enterprises. For example, IGAP can be used for
closed video broadcasting. IGAP provides a mechanism to allow the
access to the video broadcasting, only if the user is authenticated
to join the video broadcasting.
IGAP transactions flow between an IGAP host client and an IGAP
router. The IGAP router is assumed to be one hop from the IGAP host,
such that the host cannot bypass the IGAP router. An IGAP host MUST
authenticate itself to an IGAP router in order to join a multicast
group.
2. IGAP Message Format
IGAP messages are encapsulated in IP datagrams, with IGMP's IP
protocol number (2). All IGAP messages described in this document are
sent with IP TTL 1, and they contain the IP Router Alert option [RFC
2113] in their IP header.
All IGAP message packets have the following format. The first 8
octets consist of the same fields as IGMPv2 [IGMPv2].
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 (bit)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Max Resp Time | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Subtype | Reserved-1 | Challenge ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Account Size | Message Size | Reserved-2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. User Account (16 bytes) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Message (64 bytes) .
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. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2.1 Type
There are three types of IGAP messages.
0x40 = IGAP Membership Report (IGAP Join)
0x41 = IGAP Membership Query (IGAP Query)
0x42 = IGAP Leave Group (IGAP Leave)
Unrecognized message types should be silently ignored.
2.2 Max Response Time
The meaning and the usage of Max Response Time are the same as those
of the IGMP messages as described in RFC 2236 [IGMPv2].
2.3 Checksum
Checksum covers the IGAP message (the entire IPv4 payload). The
algorithm is the same as described in RFC2236 [IGMPv2].
2.4 Group Address
In a Basic Query message described in section 2.6, the group address
field is set to zero. In both Authentication Message and Accounting
Message described in section 2.6, the group address field holds the
IP multicast address of an IGAP Join. In a Membership Report or Leave
Group message, the group address field holds the IP multicast group
address of interest or the group being left.
2.5 Version
This field indicates the version of IGAP. It is set to 0x10 to
indicate the IGAP version 1.
2.6 Subtype
This field indicates the subtype of message transferred within the
IGAP packet. Usage of this field is described later.
The following 3 Subtypes are only used in IGAP join (Type 0x40).
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0x02 : Password Mechanism Join
(Password-Join)
0x03 : Challenge-Response Mechanism Join Challenge Request
(Challenge-Request-Join)
0x04 : Challenge-Response Mechanism Join Response
(Challenge-Response-Join)
The following 4 Subtypes are only used in IGAP Query (Type 0x41).
0x21 : Basic Query
0x23 : Challenge-Response Mechanism Challenge
(Challenge)
0x24 : Authentication Message
0x25 : Accounting Message
The following 4 Subtypes are used in IGAP Leave (Type 0x42).
0x41 : Basic Leave
0x42 : Password Mechanism Leave
(Password-Leave)
0x43 : Challenge-Response Mechanism Leave Challenge Request
(Challenge-Request-Leave)
0x44 : Challenge-Response Mechanism Leave Response
(Challenge-Response-Leave)
2.7 Reserved-1
This field should be set to zero. It is ignored when received.
2.8 Challenge ID
This field is meaningful only when Challenge-Response authentication
mechanism is used. The value is set according to the
Challenge-Response protocol. If this field is not used, it is set to
the default value of zero.
2.9 Account Size
This field indicates the valid length in units of bytes of the User
Account field described in section 2.12. The value must be less than
or equal to 16. If this field is not used, it is set to the default
value of zero.
2.10 Message Size
This field indicates the valid length in units of bytes of the
Message field described in section 2.13. The value must be less than
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or equal to 64. If this field is not used, it is set to the default
value of zero.
2.11 Reserved-2
This field should be set to zero. It is ignored when received.
2.12 User Account
This field contains the user account information. The size of this
field is 16 bytes. The length of the valid information is decided by
the Account Size field described in section 2.9. If the user account
occupies less than 16 bytes, the field is padded with zero.
2.13 Message
This field contains information specific to the IGAP message type.
The size of this field is 64 bytes. The length of the valid
information is decided by the Message Size field described in section
2.10. If message information occupies less than 64 bytes, the field
is padded with zero.
3. Protocol Description
Since IGMP is not needed when IGAP is used, an IGAP router should
ignore all IGMP messages received on interfaces where IGAP is
configured. IGAP messages can be differentiated from IGMP messages
by the values of the "type" field specified above.
IGAP tracks an individual host's group membership information, in
order to implement a "fast leave" feature. In other words, IGAP
does not implement the Group-Specific Query feature of IGMPv2. When
an IGAP router receives an IGAP Leave message, it deletes the
corresponding state information instead of sending a Group-Specific
Query. To facilitate tracking individual host's group membership,
IGAP does not support the Host Suppression feature of IGMP. The
current version of IGAP does not support source filter features,
although such feature will be supported in the future version of
IGAP.
IGAP specifies different behaviors for IGAP hosts and for IGAP
routers. If an IGAP router needs to join some multicast group, it
can perform both parts of the protocol.
3.1 User Authentication Mechanisms
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Currently IGAP supports two user authentication mechanisms for Join
operation: simple and basic password authentication mechanism [PAP],
and a more advanced challenge-response authentication mechanism
[CHAP]. These mechanisms are not used at the same time. Only one
mechanism may be configured for use in a specific network. An IGAP
implementation must support the password authentication mechanism,
while the challenge-response authentication mechanism is optional.
IGAP is intended for use with standard AAA servers such as RADIUS
[RADIUS] servers, which, with necessary extensions, can be used to
achieve the authentication, authorization and accounting functions
described in this document. However, IGAP is not limited to use with
standard AAA servers. It can be used with any back-end
Authentication, Authorization, and Accounting functions or
mechanisms. These functions or mechanisms can be located in different
servers, within one server, or even within the IGAP routers. In this
document, we use AAA servers as an example for these functions or
mechanisms.
3.2 IGAP Host Protocol Description
This section describes the IGAP host behavior. Based on the
configured authentication mechanism, an IGAP host behaves
differently.
3.2.1 Password Authentication in Hosts
When an IGAP host joins a multicast group, it should immediately
transmit an unsolicited IGAP Membership Report that has a Subtype
field of 0x02 (Password Mechanism Join) to the corresponding group.
The User Account field is filled with the user account (user ID)
while the Account Size field is set to the length of the user
account. The Message field is filled with the user password while the
Message Size field is set to the length of the password.
When a host receives an IGAP Query, it sets delay timers as described
in RFC2236 [IGMPv2]. If a timer for the group is already running, it
is reset to the random value only if the requested Max Response Time
is less than the remaining value of the running timer. When a group's
timer expires, the host sends a Membership Report that has a Subtype
field of 0x02. In this message, the User Account field is filled with
the user account (user ID) while the Account Size field is set to the
length of the user account.
When an IGAP host leaves from a multicast group, it sends an IGAP
Leave Group message to the all-routers multicast group
(224.0.0.2). Normally an IGAP host sends a Leave message that has a
Subtype field of 0x41 (Basic Leave). In Basic Leave, the User Account
field is filled with the user account (user ID) while the Account
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Size field is set to the length of the user account. In scenarios
where Leave message authentication is required, an IGAP host can send
a Leave message that has a Subtype field of 0x42 (Password Mechanism
Leave). In Password Mechanism Leave, the User Account and Account
Size fields are set to the values as in Basic Leave. The Message
field is filled with the user password while the Message Size field
is set to the length of the password. An IGAP implementation must
support Basic Leave. Password Mechanism Leave is optional.
3.2.2 Challenge-Response Authentication in Hosts
When an IGAP host joins a multicast group, it sends a
Challenge-Request-Join that has a Subtype field of 0x03
(Challenge-Response Mechanism Join Challenge Request) to the
corresponding group. The user Account field is filled with the user
account (user ID) while the Account Size field is set to the length
of the user account. The message field is not used.
When the IGAP host receives a Challenge that has a Subtype of 0x23
(Challenge-Response Mechanism Challenge) as a response to the
Challenge-Request-Join, the IGAP host sends a Challenge-Response-Join
that has a Subtype of 0x04 (Challenge-Response Mechanism Join
Response). The Challenge ID field is set to the same value of
Challenge ID on the Challenge packet. The user Account field is
filled with the user account (user ID) while the Account Size field
is set to the length of the user account. The Message field is set
the results of MD5 calculation. The Message Size field is set to
0x10.
When a host receives an IGAP Query, it follows the behavior described
above to set the delay timer. When a group's timer expires, the host
sends a Membership Report that has a Subtype field of 0x03. In this
message, the User Account field is filled with the user account (user
ID) while the Account Size field is set to the length of the user
account.
When an IGAP host leaves from a multicast group, it sends an IGAP
Leave Group message to the all-routers multicast group
(224.0.0.2). Normally an IGAP host sends a Basic Leave message as
described above. In scenarios where Leave message authentication is
required, an IGAP host can send a Leave message that has a Subtype
field of 0x43 (Challenge-Response Mechanism Leave Challenge
Request). The User Account field is filled with the user account
(user ID) while the Account Size field is set to the length of the
user account. The other fields are not used. When the IGAP host
receives a Challenge that has a Subtype of 0x23 (Challenge-Response
Mechanism Challenge) as a response to the Challenge-Response Leave,
it sends a Leave message that has a Subtype field of 0x44
(Challenge-Response Mechanism Leave Response). The User Account field
and Account Size field are the same. The Message field is set to the
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results of MD5 calculation. The Message Size field is set to 0x10.
An IGAP implementation must support Basic Leave. Challenge-Response
Authentication Mechanism Leave is optional.
3.3 IGAP Router Protocol Description
IGAP routers use IGAP to learn which groups have members on each of
their interfaces. They can be physical interfaces or virtual
interfaces such as VLANs. An IGAP router keeps a list of multicast
group memberships for each attached network, and a timer for each
membership. Each group membership state has the conceptual following
format:
(group address, user-id, host IP, timer)
IGAP routers periodically [Query Interval] send an IGAP Membership
Query on each attached network to solicit membership information. On
startup, a router SHOULD send [Startup Query Count] IGAP Membership
Queries spaced closely together [Startup Query Interval] in order to
quickly and reliably determine membership information. [Query
Interval], [Startup Query Count] and [Startup Query Interval] are
same as RFC 2236 [IGMPv2].
An IGAP Membership Query is addressed to the all-systems multicast
group (224.0.0.1), has a Group Address field of 0, has a Max Response
Time of [Query Response Interval], and has a IGAP Type field of 0x21
(Basic Query). Other fields are not used. [Query Response Interval]
is same as RFC 2236 [IGMPv2].
When an IGAP router receives an IGAP Membership Report or an IGAP
Group Leave, it takes different actions based on the configured
authentication mechanism.
3.3.1 Password Authentication in Routers
When an IGAP router receives a Password Mechanism Join (an IGAP join
that has a Subtype field of 0x02), if the router already has the
corresponding group membership state, it refreshes the associated
timer.
If the router does not have group membership state, it forwards the
user's group join request as well as its user authentication
information, including its user account and password, to the back-end
AAA server. Based on the AAA server's authentication and
authorization results, the IGAP router grants or denies the user's
access request. When the IGAP router grants the request, it adds the
group being reported to the list of multicast group memberships on
the interface on which it received the Report and sets the timer for
the membership to the [User Membership Interval].
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When an IGAP router receives an IGAP Leave message for a group that
has group members on the reception interface, it deletes the
corresponding group membership state.
If Leave message authentication is required, an IGAP Leave
(Password-Leave) must have a Subtype field of 0x42, and includes a
user authentication information which is same to a user
authentication on Password-Join, and the router forwards the user's
group leave information as well as the user authentication
information to the back-end AAA server. If the group leave request is
authenticated and authorized, the router deletes the corresponding
group membership state. Otherwise, the leave request is ignored.
3.3.2 Challenge-Response Authentication in Routers
When an IGAP router receives a Challenge-Response Mechanism Join
Challenge Request Mechanism Join (a Challenge-Request-Join that has
a Subtype field of 0x03), the router tries to establish
Challenge-Response communication for a Join process, then the router
sends a Challenge-Response Mechanism Challenge (a Challenge that
has a Type field of 0x41, a Subtype field of 0x23, a Challenge ID
field of an ID [CHAP], a User Account set to the same user ID in the
Challenge-Response-Join, and a Message set to a Challenge value
[CHAP]).
When the IGAP router receives a Challenge-Response Mechanism Join
Response (a Challenge-Response-Join that has a Subtype field of
0x04), if the router already has the corresponding group membership
state, it refreshes the associate timer.
If the router does not have the group membership state, it forwards
the user's group join request information as well as its user
authentication information including its user account and password to
the back-end AAA server. Based on the AAA server's results of
authentication and authorization processes, the IGAP router grants or
denies the user's access request. When the IGAP router grants the
request, it adds the group being reported to the list of multicast
group memberships on the interface on which it received the Report
and sets the timer for the membership to the [User Membership
Interval].
When an IGAP router receives an IGAP Leave message for a group that
has group members on the reception interface, it deletes the
corresponding group membership state.
If Leave message authentication is required, a host oriented
Challenge-Response communication is establish between a host and the
IGAP router. When an IGAP router receives an Challenge-Response
Mechanism Leave (Challenge-Request-Leave that has a Subtype field of
0x43), the router sends a Challenge-Response Mechanism Challenge (a
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Challenge that has a Type field of 0x41, a Subtype field of 0x23, a
Challenge ID field of an ID [CHAP], a User Account set to the same
user ID in the Challenge-Request-Leave, and a Message set to a
Challenge value [CHAP]).
When the IGAP router receives a Challenge-Response Mechanism Leave
Response (a Challenge-Response-Leave that has a Subtype field of
0x44, the User Account field and Account Size field are the same. The
Message field is set to the results of MD5 calculation. The Message
Size field is set to 0x10), and the router forwards the user's group
leave information as well as the user authentication information to
the back-end AAA server. If the group leave request is authenticated
and authorized, the router deletes the corresponding group membership
state. Otherwise, the leave request is ignored.
An IGAP implementation must support Basic Leave. Challenge-Response
Authentication Mechanism Leave is optional.
3.4 Status Notifications
In controlled or managed multicast environments, it is very important
to notify a user of its service statuses. IGAP supports the following
status notifications.
3.4.1 Authentication Result Notification
When an IGAP router receives the authentication result from the
back-end AAA server, it notifies the user of the result by unicasting
an Authentication message to the host.
The Authentication message has a Type field of 0x41 (IGAP Query) and
a Subtype field of 0x24. The Group Address field contains the
corresponding group address for authentication. The Max Resp Time
field is not used and is ignored by IGAP hosts. It can be set to any
value or set to the default value 0x64. The User Account contains the
user account (user ID) for authentication and the Account Size field
is set the length of the user account.
The Message Size field is set to 0x01. The Message field has the
following values:
0x11: Authentication success.
0x21: Authentication failure.
An IGAP implementation must support the above mandatory values. It
supports the any other vendor specific values. Appropriate value is
chosen to reflect the result from the AAA server as well as other
vendor specific processes. The process adopted by the IGAP hosts upon
receiving this packet type is up to implementation. However, it must
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not affect other IGAP process.
3.4.2 Accounting Status Notification
An IGAP router informs the accounting server to start accounting when
it starts forwarding related multicast traffic into the host's
network. When the IGAP host leaves the multicast group (either via
silent departure or an explicit leave), the router informs the
accounting server to stop accounting. Once it receives the response
from the accounting server, it notifies the IGAP host by unicasting
an Accounting message.
The Accounting message has a Type field of 0x41 (IGAP Query) and a
Subtype field of 0x25. The Group Address field, the Max Resp Time
field, the User Account field, and the Account Size field are the
same as those in the Authentication message described in section
3.4.1.
The Message Size field is set to 0x01. The Message field has the
following values:
0x11: Accounting start
0x12: Accounting stop
An IGAP implementation must support the above mandatory values. It
supports the any other vendor specific values. The process adopted by
the IGAP host upon receiving this packet type is up to
implementation. However, it must not affect other IGAP process.
3.5 Validity Period
For each group membership state, an IGAP router may maintain another
timer: Validity Period timer. This timer indicates the valid period
of an accounting to a group membership. When the timer is expired, an
IGAP router needs to re-authenticate the group membership. The value
of the "Validity Period" can be statically configured or dynamically
set based on the results from the AAA server.
When "Validity Period" is enforced, an IGAP router checks this timer
when it receives an IGAP Join. If the timer does not expire, the IGAP
router does not ask the AAA server a user authentication by a IGAP
Join response. If the timer expires, it follows the procedures for
initial authentication described above to re-authenticate the join
request. During the re-authentication period, an IGAP router
continues forwarding the multicast traffic and does not stop
accounting. If the re-authentication succeeds, an IGAP router resets
the group timer and the Validity Period timer. If the
re-authentication fails, an IGAP router stops accounting and deletes
the group membership state.
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4. Security Considerations
IGAP is based around an asymmetrical trust model in which the IGAP
router does not trust the IGAP host, but the IGAP host trusts the
IGAP router. Therefore, it may not be suitable for use in isolation
where mutual authentication is required.
IGAP supports password and challenge-response authentication
mechanisms and inherits the security concerns of each. For multicast
content encryption related technology, please refer to other IETF
work. IGAP does not obstruct snooping of multicast traffic by
unauthorized host that have access to media shared with multicast
traffic.
Some of the security issues discussed in IGMPv2 document also apply
here. Please refer to IGMPv2 document [IGMPv2] for details.
5. IANA Considerations
This document introduces the following new Types of IGMP that require
allocation by IANA:
0x40: IGAP Membership Report (IGAP Join)
0x41: IGAP Membership Query (IGAP Query)
0x42: IGAP Leave Group (IGAP Leave)
Acknowledgments
Portions of this document are copied from RFC 2236 [IGMPv2]. The
authors would like to thank Daphne Tong, Dave Allen, Abbie Barbir,
Ghassem Koleyni, Paul Knight, Kaori Izutsu, Akihiro Tanabe, Takashi
Shimizu, and Atsushi Takahara for their kindness, patience, and time
to review the document and to provide their valuable suggestions.
Appendix 1. Example of IGAP Finite State Machines on Password
authentication
This section provides an example of IGAP Finite State Machines (FSMs)
when Password authentication mechanism is used. In this example, the
value of Validity-Period is set to infinity, and the Basic-Leave is
used. We also assume that an AAA server is used and the
Authentication and Accounting packets are operated between IGAP
routers and AAA servers.
The example is for illustration purposes only. Implementations of the
IGAP protocol are suggested but not required to follow the example.
However they should comply with the specifications presented earlier
in this document.
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A.1.1. FSM for Client
PC1[Non Member]:
if join group{
send Password-Join;
start Host-Authentication-Timer;
transition PC2;
}
PC2[Waiting Authentication Message Member]:
if Authentication-Message(Reject) received
or Host-Authentication-Timer expired{
stop Host-Authentication-Timer;
transition PC1;
}
else if Authentication-Message(Success) received{
stop Host-Authentication-Timer;
transition PC3;
}
PC3[Idle Member]:
if Basic-Query received{
start Delaying-Timer;
transition PC4;
}
else if leave group{
send Basic-Leave;
transition PC5;
}
PC4[Delaying Member]:
if leave group{
send Basic-Leave;
stop Delaying-Timer;
start Host-Accounting-Timer;
set Leave-Retransmission-Counter;
transition PC5;
}
else(Delaying-Timer expired){
send Password-Join;
stop Delaying-Timer;
transition PC2;
}
PC5[Waiting Accounting Message Member]:
if Accounting-Message(Stop) received{
stop Host-Accounting-Timer;
transition PC1;
}
else if Basic-Query received{
if (Leave-Retransmission-Counter > 0) {
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Leave-Retransmission-Counter--;
send Basic-Leave;
continue(no transition);
}
}
else(Host-Accounting-Timer expired){
if (Leave-Retransmission-Counter > 0) {
Leave-Retransmission-Counter--;
send Basic-Leave;
restart Host-Accounting-Timer;
continue(no transition);
}
else{
stop Host-Accounting-Timer;
transition PC1;
}
}
A1.2. FSM for IGAP router
PR1[No Transfer Present]:
if Password-Join received{
send Authentication Request to AAA server;
start Router-Authentication-Timer;
transition PR2;
}
else if Basic-Leave received{
if (Accounting-Retransmission-Counter >0){
Accounting-Retransmission-Counter--;
send Accounting-Request(Stop) to AAA server;
transition PR5;
}
}
PR2[Waiting Authentication-Response]:
if Access-Reject received{
send Authentication-Message(Reject);
stop Router-Authentication-Timer;
transition PR1;
}
else if Access-Accept received{
if (Immediate-Accounting == true){
send Accounting-Request(Start) to AAA server;
send Authentication-Message(Success);
stop Router-Authentication-Timer;
start Router-Accounting-Timer;
transition PR3;
}
else{
start User-Membership-Interval-Timer;
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send Authentication-Message(Success);
stop Router-Authentication-Timer;
transition PR6;
}
}
else(Router-Authentication-Timer expired){
if (Free-Ride == true) {
stop Router-Authentication-Timer;
start User-Membership-Interval-Timer;
transition PR4;
}
else{
stop Router-Authentication-Timer;
transition to PR1;
}
}
PR3[Waiting Accounting-Response(Start)]:
if Accounting-Response received from AAA server{
send Accounting-Message(Start);
stop Router-Accounting-Timer;
start User-Membership-Interval-Timer;
transition PR4;
}
else(Router-Accounting-Timer expired){
stop Router-Accounting-Timer;
if (Accounting-Anyway == true){
start User-Membership-Interval-Timer;
}
transition PR4;
}
PR4[Transfer Present]:
if Password-Join received{
restart User-Membership-Interval-Timer;
continue(no transition);
}
else if Basic-Leave received{
send Accounting-Request(Stop) to AAA server;
set Accounting-Retransmission-Counter;
stop User-Membership-Interval-Timer;
start Router-Accounting-Timer;
transition PR5;
}
else(User-Membership-Interval-Timer expired){
send Accounting-Request(Stop);
start Router-Accounting-Timer;
transition PR5;
}
PR5[Waiting Accounting-Response(Stop) for Leave]:
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if Accounting-Response received from AAA server{
send Accounting-Message(stop);
stop Router-Accounting-Timer;
transition PR1;
}
else(Router-Accounting-Timer expired){
if (Accounting-Retransmission-Counter > 0){
Accounting-Retransmission-Counter--;
send Accounting-Request(Stop) to AAA server;
start Router-Accounting-Timer;
continue(no transition);
}
else{
stop Router-Accounting-Timer;
transition PR1;
}
}
PR6[Waiting Data transmission]:
if (Data for joined group received) {
send Accounting-Request(start) to AAA server;
start Router-Accounting-Timer;
transition PR3;
}
else if Basic-Leave received{
send Accounting-Request(Stop) to AAA server;
set Accounting-Retransmission-Counter;
stop User-Membership-Interval-Timer;
start Router-Accounting-Timer;
transition PR5;
}
Appendix 2. Example of IGAP Finite State Machines on Challenge-Response
This section provides an example of IGAP Finite State Machines (FSMs)
when Challenge-Response authentication mechanism is used. In this
example, the value of Validity-Period is set to a finite value, and
the Basic-Leave is used. We also assume that an AAA server is used
and the Authentication and Accounting packets are operated between
IGAP routers and AAA servers.
The example is for illustration purposes only. Implementations of the
IGAP protocol are suggested but not required to follow the example.
However they should comply with the specifications presented earlier
in this document.
A2.1. FSM for Client
CC1[Non Member]:
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if join group{
send Challenge-Request-Join;
start Challenge-Timer;
transition CC2;
}
CC2[Waiting Challenge Member]:
if Challenge received{
send Challenge-Response-Join;
stop Challenge-Timer;
start Host-Authentication-Timer;
transition CC3;
}
else(Challenge-Timer expired){
stop Challenge-Timer;
transition CC1;
}
CC3[Waiting Authentication Message Member]:
if Authentication-Message(Reject) received
or Host-Authentication-Timer expired{
stop Host-Authentication-Timer;
transition CC1;
}
else if Authentication-Message(Success) received{
stop Host-Authentication-Timer;
transition CC4;
}
CC4[Idle Member]:
if Basic-Query received{
start Delaying-Timer;
transition CC5;
}
else if leave group{
send Basic-Leave;
start Host-Accounting-Timer;
transition CC6;
}
CC5[Delaying Member]:
if leave group{
send Basic-Leave;
stop Delaying-Timer;
start Host-Accounting-Timer;
set Leave-Retransmission-Counter;
transition CC6;
}
else(Delaying-Timer expired){
send Challenge-Request-Join;
stop Delaying-Timer;
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start Challenge-Timer;
transition CC2;
}
CC6[Waiting Accounting Message Member]:
if Accounting-Message(Stop) received{
stop Host-Accounting-Timer;
transition CC1;
}
else if Basic-Query received{
if (Leave-Retransmission-Counter > 0){
Leave-Retransmission-Counter--;
send Basic-Leave;
continue(no transition);
}
}
else(Host-Accounting-Timer expired){
if (Leave-Retransmission-Counter > 0){
Leave-Retransmission-Counter--;
send Basic-Leave;
restart Host-Accounting-Timer;
continue(no transition);
}
else{
stop Host-Accounting-Timer;
transition CC1;
}
}
A2.2. FSM for IGAP router
CR1[No Transfer Present]:
if Challenge-Request-Join received{
send Challenge;
start Response-Timer;
transition CR2;
}
else if Basic-Leave received{
if (Accounting-Retransmission-Counter > 0){
Accounting-Retransmission-Counter--;
send Accounting-Request(Stop) to AAA server;
transition CR7;
}
}
CR2[Waiting Challenge-Response]:
if Challenge-Response-Join received{
send Authentication Request;
stop Response-Timer;
start Router-Authentication-Timer;
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transition CR3;
}
else(Response-Timer expired){
stop Response-Timer;
transition CR1;
}
CR3[Waiting Authentication-Response]:
if Access-Reject received from AAA server{
send Authentication-Message(Reject);
stop Router-Authentication-Timer;
transition CR1;
}
else if Access-Accept received{
if (Immediate-Accounting == true){
send Accounting-Request(Start) to AAA server;
send Authentication-Message(Success);
stop Router-Authentication-Timer;
start Router-Accounting-Timer;
transition CR4;
}
else{
start User-Membership-Interval-Timer;
send Authentication-Message(Success);
stop Router-Authentication-Timer;
transition CR8;
}
}
else(Router-Authentication-Timer expired){
if (Free-Ride == true){
stop Router-Authentication-Timer;
start User-Membership-Interval-Timer;
start Validity-Timer;
transition CR5;
}
else{
stop Router-Authentication-Timer;
transition to CR1;
}
}
CR4[Waiting Accounting-Response(Start)]:
if Accounting-Response received from AAA server{
send Accounting-Message(Start);
stop Router-Accounting-Timer;
start User-Membership-Interval-Timer;
start Validity-Timer;
transition CR5;
}
else(Router-Accounting-Timer expired){
stop Router-Accounting-Timer;
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if (Accounting-Anyway == true){
start User-Membership-Interval-Timer;
}
start Validity-Timer;
transition CR5;
}
CR5[Transfer Present]:
if Challenge-Request-Join received{
if Validity-Timer < Validity-Period{
restart User-Membership-Interval-Timer;
continue(no transition);
}
else(Validity-Timer expired){
send Router-Accounting-Request(Stop);
stop Validity-Timer;
stop User-Membership-Interval-Timer;
start Router-Accounting-Timer
transition CR6;
}
}
else if Basic-Leave received{
if (Accounting-Retransmission-Counter > 0){
Accounting-Retransmission-Counter--;
send Accounting-Request(Stop) to AAA server;
stop User-Membership-Interval-Timer;
stop Validity-Timer;
start Router-Accounting-Timer;
transition CR7;
}
else{
transition CR1;
}
}
else(User-Membership-Interval-Timer expired){
send Accounting-Request(Stop) to AAA server;
stop Validity-Timer;
start Router-Accounting-Timer;
transition CR7;
}
CR6[Waiting Accounting-Response(Stop)]:
if Accounting-Response received from AAA server{
send Accounting-Message(Stop);
send Challenge;
stop Router-Accounting-Timer;
start Response-Timer;
transition CR2;
}
else(Router-Accounting-Timer expired){
stop Router-Accounting-Timer;
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start Validity-Timer;
transition CR5;
}
CR7[Waiting Accounting-Response(Stop) for Leave]:
if Accounting-Response received{
send Accounting-Message(stop);
stop Router-Accounting-Timer;
transition CR1;
}
else(Router-Accounting-Timer expired){
if (Accounting-Retransmission-Counter > 0){
Accounting-Retransmission-Counter--;
send Accounting-Request(Stop);
start Router-Accounting-Timer;
continue(no transition);
}
else{
transition CR1;
}
}
CR8[Waiting Data transmission]:
if Data for joined group received{
send Accounting-Request(start);
start Router-Accounting-Timer;
transition CR4;
}
else if Basic-Leave received{
if (Accounting-Retransmission-Counter > 0){
Accounting-Retransmission-Counter--;
send Accounting-Request(Stop) to AAA server;
stop User-Membership-Interval-Timer;
start Router-Accounting-Timer;
transition CR7;
}
else{
transition CR1;
}
}
Appendix 3. IGAP State Machines of Query Process
This Section describes an example of IGAP State Machines on Query
Process.
QR1[Initial]:
start IGAP{
send Basic-Query;
start Startup-Query-Interval-Timer;
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start Startup-Query-Counter;
transition QR2;
}
QR2[Startup]
if Startup-Query-Interval-Timer expired{
if Startup-Query-Counter < Startup-Query-Count{
send Basic-Query;
restart Startup-Query-Interval-Timer;
continue(no transition)
}
else{
send Basic-Query;
stop Startup-Query-Counter;
start Query-Interval-Timer;
transition QR3;
}
}
QR3[Affirmed Connection]:
if Query-Interval-Timer expired{
send Basic-Query;
restart Query-Interval-Timer;
continue(no transition);
}
Appendix 4. List of Timers, Counters
This section describes the parameters set in IGAP router and Host
when supporting IGAP processes.
A4.1. Robustness Variable
It is the same meaning as IGMPv2.
A4.2. Timers for Host
A4.2.1. Challenge-Timer
It controls waiting time from sending Join message to receiving
Challenge Message.
A4.2.2. Host-Authentication-Timer
It controls waiting time from sending Response Message to receiving
Authentication Message (accept or reject) from IGAP router.
A4.2.3. Host-Accounting-Timer
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It controls waiting time from sending Response Message to receiving
Accounting Message (start or stop) from IGAP router.
A4.2.4. Delaying-Timer
It controls waiting time from receiving Query to sending Join Message
to IGAP router. It is calculated from Max Resp Time.
A4.2.5 Leave-Retransmission-Counter
The Leave-Retransmission-Counter is the number of Leave messages a
host retransmits after sending the first Leave message. The default
value is zero.
A4.3. Timers and Counters for IGAP router
A4.3.1. Response-Timer
It controls waiting time from sending Challenge Message to receiving
Response Message.
A4.3.2. Router-Authentication-Timer
It controls waiting time from sending Authentication request to
receiving Authentication Response.
A4.3.3. Router-Accounting-Timer
It controls waiting time from sending Accounting request to receiving
Accounting Response.
A4.3.4. Validity-Timer
This is an integer multiple of Basic-Query Interval in units of
second, and used by IGAP router to determine whether user
authentication is necessary or not.
A4.3.5. Query-Interval-Timer
It is the same meaning as IGMPv2. The Query Interval is the interval
between Basic Queries.
A4.3.6. Query-Response-Interval-Timer
It is the same meaning as IGMPv2. The Max Response Time inserted into
the periodic Basic Queries.
A4.3.7. User-Membership-Interval-Timer
The User Membership Interval is the amount of time that must pass
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before a IGAP router decides there are no more users of a group on
on a network. This value MUST be ((the Robustness Variable) times
(the Query Interval)) plus (one Query Response Interval).
A4.3.8. Startup-Query-Interval-Timer
It is the same meaning as IGMPv2. The Startup Query Interval is the
interval between General Queries sent by a Querier on startup.
A4.3.9. Startup-Query-Counter
It is the same meaning as IGMPv2. The Startup Query Count is the
number of Queries sent out on startup, separated by the Startup Query
Interval.
A4.3.10 Accounting-Retransmission-Counter
The Accounting-Retransmission-Counter is the number of Accounting
messages a router retransmits after sending the first accounting
message to a host. The default value is zero.
A4.3.11 Immediate-Accounting
The Immediate-Accounting indicates whether a router will start the
accounting immediately after a JOIN request is authenticated and
authorized or start the accounting when the subscribed multicast data
starts being forwarded. The values are TRUE and FALSE. The default
value is FALSE.
A4.3.12 Free-Ride
When the value is true, when Router-Authentication-Timer is expired,
the group is free to access. This variety depends on provider's
service.
A4.3.13 Accounting-Anyway
When the value is true, accounting is carried out despite the
expiration of Router-Accounting-Timer.
Normative References
[IGMPv2]
W. Fenner, "Internet Group Management Protocol, Version 2", RFC 2236,
Xerox PARC, November 1997.
[IPRA]
D. Katz, "IP Router Alert Option", RFC 2113, Cisco Systems, February
1997.
[MD5]
R. Rivest, S. Dusse, "The MD5 Message-Digest Algorithm", RFC 1321,
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April 1992.
[RADIUS]
C. Rigney, S. Willens, A. Rubens, W. Simpson, "Remote Authentication
Dial In User Service (RADIUS)", RFC 2865, June 2000.
[PAP]
B. Lloyd and W. Simpson, "PPP Authentication Protocols", RFC1334,
October 1992.
[CHAP]
W. Simpson, "PPP Challenge Handshake Authentication Protocol (CHAP)",
RFC 1994, August 1996.
Author's Addresses
Tsunemasa Hayashi
NTT Network Innovation Laboratories
1-1 Hikari-no-oka, Yokosuka-shi, Kanagawa, 239-0847 Japan
Phone : +81 46 859 8790
Email : hayashi.tsunemasa@lab.ntt.co.jp
Daisuke Andou
NTT Access Network Service Systems Laboratories
1-6 Nakase Mihiama-ku, Chiba-shi, Chiba, 261-0023 Japan
Phone : +81 43 211 2115
Email : dandou@ansl.ntt.co.jp
Haixiang He
Nortel Networks
600 Technology Park Drive
Billerica, MA 01801, USA
Phone : +1 978 288 7482
Email : haixiang@nortelnetworks.com
Wassim Tawbi
Nortel Networks
4655 Great America Parkway
Santa Clara, CA 95054, USA
Phone : +1 408 495 2362
Email : wtawbi@nortelnetworks.com
Teruki Niki
Matsushita Electric Industrial Co.,Ltd
Multimedia Systems Research-Laboratory
4-5-15 Higashi-Shinagawa Shinagawa-ku, Tokyo, 140-8632 Japan
Phone : +81 3 5460 2741
Email : niki.teruki@jp.panasonic.com
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