group
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... destination delivery
required for conferencing applications. Group addresses are
dynamically created and deleted ...
... deleted by the use of setup messages
exchanged between a host and the WPS. Membership in a group may be
any arbitrary subset of the network hosts ...
... network hosts. A message addressed to a
group address is delivered to all hosts that are members of that
group ...
... group address is delivered to all hosts that are members of that
group, except the sender. Once a multicast address has been created ...
...
Allocation of network resources, such as streams and groups, is
accomplished via an exchange of datagram messages, called Setups,
...
... message
header, allows that message to use the resource. E.g., after an
exchange of Setups to create a group address, a message may be sent
to the group by placing the group address ...
... create a group address, a message may be sent
to the group by placing the group address in the destination field of
...
... group address, a message may be sent
to the group by placing the group address in the destination field of
that message. The Service Agent ...
... message number allows the
receiver of a group of messages to reject them as a group when they
all are being refused for the same reason. As a further efficiency
...
... receiver of a group of messages to reject them as a group when they
all are being refused for the same reason. As a further efficiency
measure, HAP permits aggregation ...
... single A/R control message. Such a message might be used, for
example, to reject a group of messages where the refusal code on each
is different.
...
...
Allocation of network resources, such as streams and groups, is
accomplished via an exchange of datagram messages, called Setup
...
... Stream Request and Reply messages are described in Section 6.1.
Group Request and Reply messages are described in Section 6.2. The
format of Notifications ...
... Delete all streams owned by this host
10 = Add member to group
11 = Remove member from group ...
... Group address/stream ID nonexistent
11 = Not member of group/not creator of stream
12 = Stream ...
... network address,
specifically including group addresses, may be used
(except the Service Agent's address ...
... addresses listed. E.g., if the list consists of only
group address G, and host A is a member of G, a stream
...
...
Caution: Group membership is only evaluated at setup time. Changes
in group membership do not cause the stream ...
... Caution: Group membership is only evaluated at setup time. Changes
in group membership do not cause the stream to be modified.
...
... hosts other than those specified via Setup
will probably be undeliverable. A stream message to a group address
that has gained new members since the stream's last Setup may be
...
... unreachable. Unreachable destinations are listed as a
group if every member of the group was unreachable, or
individually otherwise; i.e., group addresses ...
... destinations are listed as a
group if every member of the group was unreachable, or
individually otherwise; i.e., group addresses are
...
... group if every member of the group was unreachable, or
individually otherwise; i.e., group addresses are
expanded and the unreachable members are included in
the list. The list of unreachable destinations ...
... Destination Address List. The new, complete, list
of recipient hosts. Membership of group addresses is
evaluated at setup execution time. Subsequent changes
in group ...
... group addresses is
evaluated at setup execution time. Subsequent changes
in group membership do not cause the stream to be
modified. Note that using the same destination address ...
... Stream Request can result in a change in the
list of recipient hosts if membership in a group has
changed.
...
... 0 errors) or unreachable (phase 3 errors). Unreachable
destinations are listed as a group if every member of
the group was unreachable, or individually otherwise;
...
... destinations are listed as a group if every member of
the group was unreachable, or individually otherwise;
i.e., group addresses are expanded and the unreachable
...
... the group was unreachable, or individually otherwise;
i.e., group addresses are expanded and the unreachable
members are included in the list. The list of
unreachable destinations ...
... Group Setup Messages ...
... hosts and the Service Agent.
Membership in a group may be any arbitrary subset of the network
hosts ...
... hosts. A datagram message or stream message addressed to a group is
delivered to all hosts that are members of that group ...
... group is
delivered to all hosts that are members of that group (exception:
stream messages sent to a group address ...
... hosts the
stream was not set up to reach). The group setup messages, each of
which has a Request and a Reply, are Create Group ...
... group setup messages, each of
which has a Request and a Reply, are Create Group, Delete Group, Join ...
...
Figure 16 shows a typical use of group setup messages. The figure
illustrates a scenario of exchanges between three hosts and the
...
... hosts B and C. The hosts then exchange some data
messages using the group address. Note that multicast messages are
not returned to their originator. Hosts ...
... not returned to their originator. Hosts A and C then leave the
group, and Host B decides to delete the group ...
... group, and Host B decides to delete the group. As in the scenario in
Section 6.1, A/R indications have been omitted for clarity.
...
...
Part of the group creation procedure involves the Service Agent
returning to the creating host ...
... bit key along with the 16-bit
group address. The creating host must pass the key along with the
group address ...
... group address. The creating host must pass the key along with the
group address to other hosts that want to join the group ...
... group address to other hosts that want to join the group. These
other hosts must supply the key along with the group address ...
... group. These
other hosts must supply the key along with the group address in their
Join Group ...
... these operations and thereby minimize the probability that unwanted
hosts will deliberately or inadvertently become members of the group.
The procedure used by a host to distribute the group address ...
... group.
The procedure used by a host to distribute the group address and key
is not within the scope of HAP.
...
... Reply Acknowledgment |<-------|
: :
Distribute Group Adr & Key |---->|
Distribute Group Adr & Key |---------->|
...
... Group Request (C) |<-------------------|
Join Group Reply |------------------->|
Reply Acknowledgment |<-------------------|
Join ...
... Reply Acknowledgment |<-------------------|
Join Group Request (B) |<-------------|
Join Group ...
... Group Request (B) |<-------------|
Join Group Reply |------------->|
Reply Acknowledgment |<-------------|
: :
...
... Data Message 3 (C to A and B) |<----|<----|
: :
Leave Group Request (C) |<-------------------|
Leave Group Reply |------------------->|
...
... Leave Group Request (C) |<-------------------|
Leave Group Reply |------------------->|
Reply Acknowledgment |<-------------------|
Leave Group ...
... Group Reply |------------------->|
Reply Acknowledgment |<-------------------|
Leave Group Request (A) |<-------|
Leave Group Reply |------->|
...
... Leave Group Request (A) |<-------|
Leave Group Reply |------->|
Reply Acknowledgment |<-------|
Delete ...
... Group Request |<-------------|
Delete Group Reply |------------->|
Reply Acknowledgment |<-------------|
...
... Reply Acknowledgment |<-------------|
GROUP EXAMPLE
Figure 16
...
... An alternative method of adding and removing group members is the use
of Add Group Member and Remove ...
... removing group members is the use
of Add Group Member and Remove Group Member. These setup requests
...
... of Add Group Member and Remove Group Member. These setup requests
allow hosts that are already members of the group ...
... Group Member. These setup requests
allow hosts that are already members of the group to add or delete
other hosts ...
... remove a host from the
group membership list but will not alter the existence of the group.
Delete ...
... host from the
group membership list but will not alter the existence of the group.
Delete Group ...
... HAP permits any host with the proper key to delete the group at any
time. Thus, group addresses can be deleted ...
... originally created the group has left the group or has crashed.
Moreover, groups may exist for which there are currently no members
...
... group has left the group or has crashed.
Moreover, groups may exist for which there are currently no members
because each member has executed a Leave while none has executed a
Delete ...
... Delete. It is the responsibility of the hosts to coordinate and
manage the use of group addresses.
...
...
Note that group addresses, like all other resources allocated by the
network, may be reclaimed by the network ...
... network if unused for too long.
Currently, if no traffic is sent to the group address in a 6 minute
interval, the network may delete ...
... interval, the network may delete the group and notify all members
that the group no longer exists.
...
...
The Create Group Request (Figure 17) is used to establish a multicast
address. After the network has processed the Create ...
... multicast
address. After the network has processed the Create Group Request,
the Service Agent will respond by sending a Create ...
...
A host may become a member of a group, once it knows the group
address and the 48-bit key, by sending the Service Agent ...
... A host may become a member of a group, once it knows the group
address and the 48-bit key, by sending the Service Agent the Join ...
... Service Agent will respond to
the Join Group Request with a Join Group Reply (Figure 20). The host ...
... host
which creates a group automatically becomes a member of that group
without any need for an explicit Join ...
... which creates a group automatically becomes a member of that group
without any need for an explicit Join Group ...
... A member host may add another host to the group by sending the
Service Agent the Add Group Member ...
... group by sending the
Service Agent the Add Group Member Request message (Figure 21). The
Service Agent ...
... Request message (Figure 21). The
Service Agent will respond with an Add Group Member Reply (Figure
22).
...
... group, a host may choose to
drop out of the group. To do this, the host sends the Service Agent
...
... host sends the Service Agent
a Leave Group Request (Figure 23). The Service Agent will respond
with a Leave Group ...
... Group Request (Figure 23). The Service Agent will respond
with a Leave Group Reply (Figure 24).
...
...
One member host may expel another member of the group by sending the
Service Agent the Remove ...
... delete an existing group via a Delete Group Request
(Figure 27). The Service Agent will respond with a Delete ...
... (Figure 27). The Service Agent will respond with a Delete Group
Reply (Figure 28). The Service Agent will also send the other
...
... Reply (Figure 28). The Service Agent will also send the other
members of the group, if any, a notification that the group has been
...
... members of the group, if any, a notification that the group has been
deleted (see Section 6.3).
...
... S2 | REQUEST ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S3 | GROUP ADDRESS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S4 | KEY |
...
... S2[0-15] Request ID.
S3[0-15] Group Address. This field contains the 16-bit
multicast address ...
... bit
multicast address that any group member may use to
reach the other group members. Multicast addresses ...
... multicast address that any group member may use to
reach the other group members. Multicast addresses are
dynamically assigned by the network ...
... bit key assigned by the
network which is associated with the group address. It
must be provided for subsequent Join Group ...
... Delete Group requests which reference the group
address.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
...
... S2 | REQUEST ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S3 | GROUP ADDRESS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S4 | KEY |
...
... host wishes
to join. Upon successfully joining the group, the host
may send messages to the group ...
... group, the host
may send messages to the group and will receive
messages sent to the group when those messages have a
...
... may send messages to the group and will receive
messages sent to the group when those messages have a
priority of MGP or higher.
...
... priority of MGP or higher.
S4-S6 Key. This is the key associated with the group
address.
S7[0-13] Reserved. Must be zero.
...
... S7[0-13] Reserved. Must be zero.
S7[14-15] Minimum group message priority. The host will not
...
... message priority. The host will not
receive messages sent to the group that have a message
priority less than MGP. Send another Join Group ...
... group that have a message
priority less than MGP. Send another Join Group
Request message to change the minimum priority ...
... S2 | REQUEST ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S3 | GROUP ADDRESS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S4 | KEY |
...
...
ADD GROUP MEMBER REQUEST
Figure 21
...
... host will join.
Upon successfully joining the group, the host may send
messages to the group ...
... group, the host may send
messages to the group and will receive messages sent to
the group by other hosts ...
... messages to the group and will receive messages sent to
the group by other hosts (the initial minimum priority
...
... will be 0).
S4-S6 Key. This is the key associated with the group
address.
S7[0-15] Host ...
...
ADD GROUP MEMBER REPLY
Figure 22
...
... group (or was already a member)
9 = Bad key
10 = Group address nonexistent
11 = Requestor is not a member of the group
...
... 10 = Group address nonexistent
11 = Requestor is not a member of the group
17 = Insufficient network resources
...
... S2 | REQUEST ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S3 | GROUP ADDRESS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S4 | KEY |
...
... +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
LEAVE GROUP REQUEST
Figure 23
...
... S0[0-7] Setup Type = 1 (Request).
S0[8-15] Request Type = 4 (Leave Group).
S1[0-15] Setup Checksum ...
...
S3[0-15] Group Address. This is the group that the host wishes
to cease being a member of. After leaving the group ...
... group that the host wishes
to cease being a member of. After leaving the group,
the host will cease receiving ...
... host will cease receiving messages sent to the
group and will be unable to send to the group.
...
... receiving messages sent to the
group and will be unable to send to the group.
S4-S6 Key. This is the key associated with the group
address ...
... group.
S4-S6 Key. This is the key associated with the group
address.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
...
... +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
LEAVE GROUP REPLY
Figure 24
...
... S2 | REQUEST ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S3 | GROUP ADDRESS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S4 | KEY |
...
...
REMOVE GROUP MEMBER REQUEST
Figure 25
...
... S0[0-7] Setup Type = 1 (Request).
S0[8-15] Request Type = 4 (Leave Group).
S1[0-15] Setup Checksum ...
... host
will cease receiving messages sent to the group and
will be unable to send to the group.
...
... receiving messages sent to the group and
will be unable to send to the group.
S4-S6 Key. This is the key associated with the group
address ...
...
REMOVE GROUP MEMBER REPLY
Figure 26
...
... group (or was not a member)
9 = Bad key
10 = Invalid group address
11 = Requestor is not a member of the group
...
... 10 = Invalid group address
11 = Requestor is not a member of the group
17 = Insufficient network resources
...
... S2 | REQUEST ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S3 | GROUP ADDRESS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S4 | KEY |
...
... multicast address to
delete. If the group is deleted, the other remaining
members of the group ...
... group is deleted, the other remaining
members of the group, if any, will be notified of the
group's deletion.
...
...
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
S3 | group address |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
...
... For notification types 5 and 6, which refer to all
streams or groups, NOTIFICATION INFO is zero.
...
... 1 = streams owned by host
2 = groups to which the host belongs
3 = error in Information Request message ...
... SN Zero or more instances of either the stream information
or group information structure.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
...
... 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
0 | GROUP ADDRESS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
1 | 0 | MGP |
...
... +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
GROUP INFORMATION
Figure 34
...
... The allocation and state of network resources (streams and groups)
are separate from the state of the host ...
...
One change under consideration is the addition of a "conference"
resource, which would own some number of streams and groups and
improve the network's ability to meet the needs of video conference
...
... new member, would result in modifying all the streams in the
conference to include the new member, modifying the conference's
primary group address to add the new member, etc., in a single
network operation. Such a capability would not only simplify
...