Dynamic assignment of multicast addresses

• US 5,835,723 A
• Filed: 12/28/1995
• Issued: 11/10/1998
• Est. Priority Date: 12/28/1995
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Andrews, Michael, Davison, Eric, Danneels, Gunner, Sampat, Ketan
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Maung, Zarni
• Application Number:
  US08/579,725
• Time in Patent Office: 1,048 Days
• Field of Search: 395/200.1, 395/200.11, 395/200.12, 395/200.16, 395/200.3, 395/200.69, 395/200.54, 395/200.56, 395/200.57, 370/252, 370/443, 370/453, 370/462, 340/825.5, 340/825.52, 340/825.53
• US Class Current: 709/226
• CPC Class Codes: G06F 9/542 Event management; Broadcasting; Multicasting; Notifications
• CPC Class Codes: H04L 12/185 with management of multicast group membership
• CPC Class Codes: H04L 12/1877 Measures taken prior to transmission
• CPC Class Codes: H04L 61/5007 Internet protocol [IP] addresses
• CPC Class Codes: H04L 61/5053 Lease time; Renewal aspects
• CPC Class Codes: H04L 61/5069 for group communication, multicast communication or broadcast communication

Abstract

A distributed protocol for allocation of multicast addresses. A first node of a network sends an address request message identifying (1) a requested in multicast address, and (2) a multicast group identifier to which the requestor belongs. The request is in multicast on a network address reserved for address resolution. All other nodes of the network monitor the reserved network address for address request messages. If a second node receiving the address request message has already allocated the requested multicast address, then the second node sends an acknowledgment message identifying (1) the already allocated in multicast address, and (2) the multicast group for which the address has been allocated. This acknowledgment is transmitted on the same reserved network address on which the address request was sent. The first node, monitoring the reserved network address, receives the acknowledgment message. If the multicast group identified in the acknowledgment message matches the multicast group to which the first node belongs, then the first node also allocates the requested network address. If the multicast group identified in the acknowledgment message does not match the multicast group to which the first node belongs, then the first node abandons the requested network address. If the first node does not receive an acknowledgment message in response to any number of address request messages repeated for the same requested multicast address, then the first node either (1) allocates the requested network address, or (2) abandons the requested network address, if the node is not the first member of a multicast group to request allocation of the address. If address allocation succeeds, then the first node uses the allocated network address for multicasting. If address allocation fails, then the first node is free to select a different multicast address to request.

Claims

1. A computer-implemented process for allocating multicast addresses, comprising the steps of:

(a) selecting a potential multicast address by a first node of a network;

(b) transmitting by the first node an address request message on a reserved address of the network, wherein;

the address request message identifies the potential multicast address as a requested multicast address;

the address request message identifies a requested handle associated with the requested multicast address, wherein the requested handle comprises a unicast address for the first node and a unique value generated by the first node, whereby the requested handle is different from any other requested handle ever generated by any node of the network including the first node;

one or more other nodes of the network monitor the reserved address for address request messages;

at least one other node of the network transmits an acknowledgment message on the reserved address, if the requested multicast address is already allocated by the other node;

the acknowledgment message identifies the requested multicast address as an already allocated multicast address; and

the acknowledgment message identifies an already allocated handle associated with the already allocated multicast address;

(c) monitoring the reserved address by the first node for the acknowledgment message; and

(d) abandoning the requested multicast address by the first node, if the first node receives the acknowledgment message from at least one other node of the network.

2. The process of claim 1, further comprising the step of:

(e) allocating the requested multicast address as an allocated multicast address by the first node and performing multicast operations by the first node using the allocated multicast address, if the first node fails to receive the acknowledgment message.

3. The process of claim 2, wherein steps (b) and (c) are implemented two or more times before step (e) is implemented.

4. The process of claim 2, wherein step (e) further comprises the steps of:

(1) monitoring the reserved address by the first node for subsequent address request messages from other nodes requesting the allocated multicast address; and

(2) transmitting an acknowledgment message by the first node on the reserved address, if the first node receives an address request message from another node requesting the allocated multicast address.

5. The process of claim 1, wherein:

step (d) comprises the step of abandoning the requested multicast address by the first node, if the first node receives the acknowledgment message from at least one other node of the network, wherein;

the already allocated multicast address identified in the acknowledgment message matches the requested multicast address; and

the already allocated handle identified in the acknowledgment message fails to match the requested handle; and

further comprising the steps of;

(e) abandoning the requested multicast address by the first node, if the first node fails to receive the acknowledgment message from at least one other node of the network; and

(f) allocating the requested multicast address as an allocated multicast address by the first node and performing multicast operations by the first node using the allocated multicast address, if the first node receives the acknowledgment message, wherein;

the already allocated multicast address identified in the acknowledgment message matches the requested multicast address; and

the already allocated handle identified in the acknowledgment message matches the requested handle.

6. The process of claim 1, wherein no single node of the network is responsible for allocating multicast addresses for all other nodes.

7. The process of claim 1, wherein step (d) comprises the further steps of:

(1) selecting a new potential multicast address by the first node; and

(2) implementing steps (b)-(c) using the new potential multicast address as the requested multicast address.

8. The process of claim 1, wherein the network comprises one or more subnets, wherein each subnet has a reserved address used for address allocation resolution as implemented by steps (a)-(d).

9. The process of claim 8, wherein the reserved address for a first subnet is equal to the reserved address for a second subnet, if the scope of the first subnet does not intersect the scope of the second subnet.

10. The process of claim 1, wherein:

the address request message comprises the requested address, the requested handle, a unicast address for the first node, and a retry count; and

the acknowledgment message comprises the already allocated address and the already allocated handle.

11. The process of claim 1, wherein, when the first node receives an address request message from a second node of the network requesting a multicast address identical to the multicast address requested by the first node while the first node is waiting for an acknowledgment message in response to its address request message:

the first node abandons the requested multicast address, if the first node is operating in a master allocation mode, the second node is operating in the master allocation mode, and the unicast address of the first node is larger than the unicast address of the second node;

the first node reissues its address request message, if the first node is operating in the master allocation mode, the second node is operating in the master allocation mode, and the unicast address of the first node is smaller than the unicast address of the second node;

the first node abandons the requested multicast address, if the first node is operating in the master allocation mode and the second node is operating in a slave allocation mode;

the first node continues its processing unmodified, if the first node is operating in the slave allocation mode and the second node is operating in the master allocation mode; and

the first node continues its processing unmodified, if the first node is operating in the slave allocation mode and the second node is operating in the slave allocation mode.

12. The process of claim 1, wherein the first node transmits an address query to determine whether a multicast address is allocated by another node of the network.

13. An apparatus for allocating multicast addresses, comprising:

(a) means for selecting a potential multicast address by a first node of a network;

(b) means for transmitting by the first node an address request message on a reserved address of the network, wherein;

the address request message identifies the potential multicast address as a requested multicast address;

the address request message identifies a requested handle associated with the requested multicast address, wherein the requested handle comprises a unicast address for the first node and a unique value generated by the first node, whereby the requested handle is different from any other requested handle ever generated by any node of the network including the first node;

one or more other nodes of the network monitor the reserved address for address request messages;

at least one other node of the network transmits an acknowledgment message on the reserved address, if the requested multicast address is already allocated by the other node;

the acknowledgment message identifies the requested multicast address as an already allocated multicast address; and

the acknowledgment message identifies an already allocated handle associated with the already allocated multicast address;

(c) means for monitoring the reserved address by the first node for the acknowledgment message; and

(d) means for abandoning the requested multicast address by the first node, if the first node receives the acknowledgment message from at least one other node of the network.

14. The apparatus of claim 13, further comprising:

(e) means for allocating the requested multicast address as an allocated multicast address by the first node and performing multicast operations by the first node using the allocated multicast address, if the first node fails to receive the acknowledgment message.

15. The apparatus of claim 14, wherein the processing of means (b) and (c) is implemented two or more times before the processing of means (e) is implemented.

16. The apparatus of claim 14, wherein means (e):

(1) monitors the reserved address by the first node for subsequent address request messages from other nodes requesting the allocated multicast address; and

(2) transmits an acknowledgment message by the first node on the reserved address, if the first node receives an address request message from another node requesting the allocated multicast address.

17. The apparatus of claim 13, wherein:

means (d) abandons the requested multicast address by the first node, if the first node receives the acknowledgment message from at least one other node of the network, wherein;

the already allocated multicast address identified in the acknowledgment message matches the requested multicast address; and

the already allocated handle identified in the acknowledgment message fails to match the requested handle; and

further comprising;

(e) means for abandoning the requested multicast address by the first node, if the first node fails to receive the acknowledgment message from at least one other node of the network; and

(f) means for allocating the requested multicast address as an allocated multicast address by the first node and performing multicast operations by the first node using the allocated multicast address, if the first node receives the acknowledgment message, wherein;

the already allocated multicast address identified in the acknowledgment message matches the requested multicast address; and

the already allocated handle identified in the acknowledgment message matches the requested handle.

18. The apparatus of claim 13, wherein no single node of the network is responsible for allocating multicast addresses for all other nodes.

19. The apparatus of claim 13, wherein means (d):

(1) selects a new potential multicast address by the first node; and

(2) implements the processing of means (b)-(c) using the new potential multicast address as the requested multicast address.

20. The apparatus of claim 13, wherein the network comprises one or more subnets, wherein each subnet has a reserved address used for address allocation resolution as implemented by means (a)-(d).

21. The apparatus of claim 20, wherein the reserved address for a first subnet is equal to the reserved address for a second subnet, if the scope of the first subnet does not intersect the scope of the second subnet.

22. The apparatus of claim 13, wherein:

the address request message comprises the requested address, the requested handle, a unicast address for the first node, and a retry count; and

the acknowledgment message comprises the already allocated address and the already allocated handle.

23. The apparatus of claim 13, wherein, when the first node receives an address request message from a second node of the network requesting a multicast address identical to the multicast address requested by the first node while the first node is waiting for an acknowledgment message in response to its address request message:

the first node abandons the requested multicast address, if the first node is operating in a master allocation mode, the second node is operating in the master allocation mode, and the unicast address of the first node is larger than the unicast address of the second node;

the first node reissues its address request message, if the first node is operating in the master allocation mode, the second node is operating in the master allocation mode, and the unicast address of the first node is smaller than the unicast address of the second node;

the first node abandons the requested multicast address, if the first node is operating in the master allocation mode and the second node is operating in a slave allocation mode;

the first node continues its processing unmodified, if the first node is operating in the slave allocation mode and the second node is operating in the master allocation mode; and

the first node continues its processing unmodified, if the first node is operating in the slave allocation mode and the second node is operating in the slave allocation mode.

24. The apparatus of claim 13, wherein the first node transmits an address query to determine whether a multicast address is allocated by another node of the network.

25. A storage medium encoded with machine-readable computer program code for allocating multicast addresses, comprising:

(a) means for causing a computer to select a potential multicast address by a first node of a network;

(b) means for causing the computer to transmit by the first node an address request message on a reserved address of the network, wherein;

the address request message identifies the potential multicast address as a requested multicast address;

the address request message identifies a requested handle associated with the requested multicast address, wherein the requested handle comprises a unicast address for the first node and a unique value generated by the first node, whereby the requested handle is different from any other requested handle ever generated by any node of the network including the first node;

one or more other nodes of the network monitor the reserved address for address request messages;

at least one other node of the network transmits an acknowledgment message on the reserved address, if the requested multicast address is already allocated by the other node;

the acknowledgment message identifies the requested multicast address as an already allocated multicast address; and

the acknowledgment message identifies an already allocated handle associated with the already allocated multicast address;

(c) means for causing the computer to monitor the reserved address by the first node for the acknowledgment message; and

(d) means for causing the computer to abandon the requested multicast address by the first node, if the first node receives the acknowledgment message from at least one other node of the network.

26. The storage medium of claim 25, further comprising:

(e) means for causing the computer to allocate the requested multicast address as an allocated multicast address by the first node and performing multicast operations by the first node using the allocated multicast address, if the first node fails to receive the acknowledgment message.

27. The storage medium of claim 26, wherein the processing of means (b) and (c) is implemented two or more times before the processing of means (e) is implemented.

28. The storage medium of claim 26, wherein means (e) causes the computer to:

(1) monitor the reserved address by the first node for subsequent address request messages from other nodes requesting the allocated multicast address; and

(2) transmit an acknowledgment message by the first node on the reserved address, if the first node receives an address request message from another node requesting the allocated multicast address.

29. The storage medium of claim 25, wherein:

means (d) causes the computer to abandon the requested multicast address by the first node, if the first node receives the acknowledgment message from at least one other node of the network, wherein;

the already allocated multicast address identified in the acknowledgment message matches the requested multicast address; and

the already allocated handle identified in the acknowledgment message fails to match the requested handle; and

further comprising;

(e) means for causing the computer to abandon the requested multicast address by the first node, if the first node fails to receive the acknowledgment message from at least one other node of the network; and

(f) means for causing the computer to allocate the requested multicast address as an allocated multicast address by the first node and performing multicast operations by the first node using the allocated multicast address, if the first node receives the acknowledgment message, wherein;

the already allocated multicast address identified in the acknowledgment message matches the requested multicast address; and

the already allocated handle identified in the acknowledgment message matches the requested handle.

30. The storage medium of claim 25, wherein no single node of the network is responsible for allocating multicast addresses for all other nodes.

31. The storage medium of claim 25, wherein means (d) causes the computer to:

(1) select a new potential multicast address by the first node; and

(2) implement the processing of means (b)-(c) using the new potential multicast address as the requested multicast address.

32. The storage medium of claim 25, wherein the network comprises one or more subnets, wherein each subnet has a reserved address used for address allocation resolution as implemented by means (a)-(d).

33. The storage medium of claim 32, wherein the reserved address for a first subnet is equal to the reserved address for a second subnet, if the scope of the first subnet does not intersect the scope of the second subnet.

34. The storage medium of claim 25, wherein:

the address request message comprises the requested address, the requested handle, a unicast address for the first node, and a retry count; and

the acknowledgment message comprises the already allocated address and the already allocated handle.

35. The storage medium of claim 25, wherein, when the first node receives an address request message from a second node of the network requesting a multicast address identical to the multicast address requested by the first node while the first node is waiting for an acknowledgment message in response to its address request message:

the first node abandons the requested multicast address, if the first node is operating in a master allocation mode, the second node is operating in the master allocation mode, and the unicast address of the first node is larger than the unicast address of the second node;

the first node reissues its address request message, if the first node is operating in the master allocation mode, the second node is operating in the master allocation mode, and the unicast address of the first node is smaller than the unicast address of the second node;

the first node abandons the requested multicast address, if the first node is operating in the master allocation mode and the second node is operating in a slave allocation mode;

the first node continues its processing unmodified, if the first node is operating in the slave allocation mode and the second node is operating in the master allocation mode; and

the first node continues its processing unmodified, if the first node is operating in the slave allocation mode and the second node is operating in the slave allocation mode.

36. The storage medium of claim 25, wherein the first node transmits an address query to determine whether a multicast address is allocated by another node of the network.