US20120166515A1

US20120166515A1 - Providing and Resolving an IP Address for Swarm-Based Services

Info

Publication number: US20120166515A1
Application number: US12/976,708
Authority: US
Inventors: Pradeep Iyer; Santashil PalChaudhuri
Original assignee: Individual
Current assignee: Hewlett Packard Enterprise Development LP
Priority date: 2010-12-22
Filing date: 2010-12-22
Publication date: 2012-06-28
Also published as: US9667512B2; US20130268660A1

Abstract

Providing and maintaining an IP address for swarm-based services. A swarm is a group of digital devices operating cooperatively on a network, such as a group of wireless access points. Services may be distributed over members of the swarm, with each service having a master which is hosted on one member of the swarm. The master broadcasts a periodic heartbeat, advertising its service and the address of the host member. If a swarm member fails to hear a particular service's heartbeat for a predetermined interval, it broadcasts a message announcing its intent to be master for the service. If the swarm member does not receive any other broadcasts from members indenting to take the role of master for the service, it takes over the role of master for the service and begins broadcasting periodic heartbeats identifying itself as the service master. If multiple swam members broadcast their intent to become master of the same service, a resolution protocol is invoked and one swarm member is selected to be master. In operation, each member of the swarm maintains a table of services and the address of the swarm member hosting the service; this information is obtained from the periodic heartbeats broadcast by each service master. When a swarm member receives a service request, the request is either redirected to the service master, or the request is terminated at the swarm member and handled.

Description

NOTICE OF RELATED APPLICATION

This application is related to U.S. patent application Ser. No. ______, entitled “Provisioning a Swarm” filed on Dec. ______, 2010, by Pradeep lyer and Santashil PalChaudhuri, the disclosure of which is specifically incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to digital networks, and in particular, to the problem of providing known IP addresses for services provided by a swarm of wireless access points.
As used herein, a swarm is defined as a set of cooperating digital devices communicating over a digital network. One example of a swarm is a group of wireless access points (AP) providing wireless services to clients. Other examples of swarms are clusters of computers operating as a render farm, or other distributed computing tasks.
The composition of the swarm may change dynamically. As an example, access points may be added dynamically to a swarm, or may be removed from service.
An important aspect of a swarm is the distribution of services across swarm members. As an example, in a swarm of wireless access points, aspects of the functionality normally provided by a separate controller such as administration and configuration may be distributed over members of the swarm. And while this functionality may be hosted by any member of the swarm, there may still be a need to provide access to these services, such as by providing fixed IP addresses. In that way, clients may use the services without needing to know which member of the swarm is hosting the service.
What is needed is a way to provide and maintain addresses for services provided by members of the swarm.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be best understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention in which:

FIG. 1 shows devices in a network operating as a swarm.

DETAILED DESCRIPTION

Embodiments of the invention relate to methods of providing and maintaining addresses for services provided by a swarm.
According to the present invention, a swarm is a group of digital devices connected to a digital network and operating in a cooperative manner. An example of a swarm is a group of wireless access points providing wireless services to clients. One or more services may be distributed over members of the swarm. While members of the swarm typically do not have fixed IP addresses, fixed addresses may be provided for swarm services. Each service on the swarm has a master, and is hosted on one member of the swarm. The master broadcasts a periodic heartbeat, advertising its service and the address of the host member. If a swarm member fails to hear a particular service's heartbeat for a predetermined interval, it broadcasts a message announcing its intent to be master for the service. If the swarm member does not receive any other broadcasts from members indenting to take the role of master for the service, it takes over the role of master for the service and begins broadcasting periodic heartbeats identifying itself as the service master. If multiple swam members broadcast their intent to become master of the same service, a resolution protocol is invoked and one swarm member is selected to be master.
In operation, each member of the swarm maintains a table of services and the address of the swarm member hosting the service; this information is obtained from the periodic heartbeats broadcast by each service master. When a swarm member receives a service request, the request is either redirected to the service master, or the request is terminated at the swarm member and handled.
FIG. 1 shows a network in which a swarm comprises a plurality of access points. Access points (APs) 100 a-100 e are purpose-made digital devices, each containing a processor 110, memory hierarchy 120, and input-output interfaces 130. In one embodiment of the invention, a MIPS-class processor such as those from Cavium or RMI is used. Other suitable processors, such as those from Acorn, Intel, or AMD may also be used. The memory hierarchy 120 traditionally comprises fast read/write memory for holding processor data and instructions while operating, and nonvolatile memory such as EEPROM and/or Flash for storing files and system startup information. Wired interfaces 140 are typically IEEE 802.3 Ethernet interfaces, used for wired connections to other network devices such as switches, or to a controller. Wireless interfaces 130 may be WiMAX, 3G, 4G, and/or IEEE 802.11 wireless interfaces. In one embodiment of the invention, APs operate under control of a LINUX operating system. APs 100 may connect to a switch 300 which provides access to network 400. It should be noted that switch 300 does not have the capabilities of a controller, but only provides L2/L3 switching.
Wireless client 200 has a similar architecture, chiefly differing in input/output devices; a laptop computer will usually contain a large LCD, while a handheld wireless scanner will typically have a much smaller display, but contain a laser barcode scanner.
While the present invention is described in terms of a swarm comprising a plurality of access points providing wireless services to clients, the invention is equally applicable to swarms of other digital devices communicating on a network.
According to the present invention, a swarm is a group of digital devices connected to a network and operating cooperatively. As shown in FIG. 1, APs 100 a-100 e form a swarm, with APs 100 a-100 d having wired connections to switch 300, and AP 100 e having only wireless connections to the other members 100 a-100 d of the swarm. Note that the network supporting the swarm may be a wired network, a wireless network, or a combination. In a preferred embodiment, the wireless network is an IEEE 802.11 Wireless network. In the example of FIG. 1, switch 300 provides access to network 400.
An important aspect of a swarm is the distribution of services over the swarm. In the example of a swarm of wireless access points (APs), such as shown in FIG. 1, aspects of controller functionality normally required to operate such a group of APs may be hosted on one or more members of the swarm. Each service is hosted on one member of the swarm.
According to the present invention the service master broadcasts a heartbeat periodically. In one embodiment of the invention, this heartbeat identifies the service, and the IP address of the swarm member hosting the service.
Other swarm members monitor the service heartbeat. If a swarm member does not receive a service heartbeat in a predetermined period, the swarm member broadcasts a message to all other swarm members indicating that the swarm member intends to be the master for that particular service. If the swarm member does not receive any other broadcasts of intent to be that service's master, the swarm member takes on the role of service master and begins broadcasting the periodic heartbeats. This process covers the cases of service startup when no previous master exists, and service recovery when the service master fails.
Note that not all swarm members may serve as masters for all services. As an example, in a swarm of access points, the design decision may be made not to permit mesh nodes, those nodes without wired Ethernet connections such as AP 100 e, to become masters for certain services. Swarm elements not possessing cryptographic hardware may not be suitable for hosting certain authentication functions, and so on. Similarly, a swarm element already acting as master for one service may be configured to not offer its services as master for another service.
Similarly, some swarm members may be favored to host services. A device with larger memory capacity or a faster processor may be favored to host some services. In one embodiment of the invention, swarm members may be divided into classes according to their suitability as masters for a particular service. Those with a higher degree of suitability will have a shorter preset time limit before broadcasting the intent to be master. As an example, assume a particular service master sends out a heartbeat every second. Assume there are three classes of swarm members, with those having the highest degree of suitability for operating as master waiting five seconds before broadcasting intent to be master, those in the middle class waiting six seconds, and those in the lower class waiting seven seconds before broadcasting intent to be master.
In the event that multiple swarm members broadcast the intent to be master, a resolution protocol must be employed. The resolution protocol for the service must be the same on all swarm members, so that each member of the swarm can apply the protocol and arrive at the same decision as to which member will be master.
Many different protocols may be used, as long as they are used uniformly for the service over all members of the swarm. Examples include choosing the master based on the identification of the swarm member, such as MAC address or IP address. As examples, high or low values may be chosen as master. Information relating to the operating history of the swarm member, such as uptime may also be used, but this requires that the information needed for the resolution protocol be included in the broadcast intent to be master message.
Depending on the service, once a master has been selected, the master may need to populate data structures with information from other swarm members. In one embodiment of the invention, when a non-master swarm member detects that a new master has been selected for a service, the swarm member sends complete datasets to the new master. Once the master has been provided with complete datasets, only changes need be sent as needed. As an example, in the case of a swarm of access points and a service providing administrative functions, when a swarm member detects a new master has been established for this service, the swarm member sends the master complete tables describing all the wireless clients connected to the access point. Once complete tables have been provided to the master, the swarm member need only send changes to the master.
As an example, assume that during swarm startup, AP 100 c is first to advertise itself as a service master for a service. AP 100 c starts service process 160. AP 100 c begins broadcasting periodic heartbeats for service 160. If AP 100 c fails, the heartbeat for service 160 from AP 100 c ceases. This causes the remaining APs to once again select a new master, such as AP 100 d starting new service process 170. Now AP 100 d begins broadcasting periodic heartbeats for service 170.
A client such as wireless client 200 is associated with a particular AP member of the swarm. As shown in FIG. 1, client 200 is associated with AP 100 a. When client 200 wishes to use a swarm service, it does that through the fixed address for that service. A request from client 200 is received by AP 100 a member of the swarm. AP 100 a uses the table of service addresses which it maintains from received heartbeats. If the AP cannot process the request itself, the request is redirected to the swarm member hosting the service, such as AP 100 d for service 170.
The present invention may be realized in hardware, software, or a combination of hardware and software. The present invention may be realized in a centralized fashion in one computer system such as AP 100 a, or in a distributed fashion where different elements are spread across several interconnected computer systems. A typical combination of hardware and software may be an access point with a computer program that, when being loaded and executed, controls the device such that it carries out the methods described herein.
The present invention also may be embedded in nontransitory fashion in a computer program product, which comprises all the features enabling the implementation of the methods described herein, and which when loaded in a computer system is able to carry out these methods. Computer program in the present context means any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following: a) conversion to another language, code or notation; b) reproduction in a different material form.
This invention may be embodied in other forms without departing from the spirit or essential attributes thereof. Accordingly, reference should be made to the following claims, rather than to the foregoing specification, as indicating the scope of the invention.

Claims

1-11. (canceled)

12. A method comprising:

listening, by a first digital device in a group of digital devices, for a periodical message identifying a service, wherein the service is to be hosted by one or more digital devices in the group of digital devices, wherein the service is associated with a static network address shared by the one or more digital devices, and wherein the periodical message comprises the static network address;

in response to the periodical message being received by the first digital device, storing the static network address associated with the service at the first digital device; and

in response to no periodical message being received by the first digital device within a predetermined time period, determining that no digital device in the one or more digital devices is hosting the service.

13. The method of claim 12, wherein a second digital device in the one or more digital devices starts hosting the service after a first digital device in the one or more digital devices stops hosting the service, thereby allowing the first digital device and the second digital device to jointly provide continuous service for clients.

14. The method of claim 13, wherein the second digital device is elected as a host for the service based on one or more of the following factors:

a capability of the second digital device;

a capacity of the second digital device;

a classification associated with the second digital device;

a function of the service;

an operating history of the second digital device;

an identifier associated with the second digital device; and

a result from a resolution protocol performed by the one or more digital devices.

15. The method of claim 14, wherein each of the one or more digital devices uses same factors to elect the host for the service.

16. The method of claim 12, wherein the static network address comprises a fixed Internet Protocol (IP) address.

17. The method of claim 12, wherein the one or more digital devices comprises access points that are not coupled to any network device having capabilities of a controller, and wherein the service comprises one or more controller functionalities.

18. The method of claim 12, wherein a plurality of services are distributed across the one or more digital devices that host the services.

19. A method comprising:

receiving, by a first digital device in a group of digital devices, a request for a service hosted by one or more digital devices in the group of digital devices, wherein the request comprises a network address corresponding to the requested service;

determining, by the first digital device, whether a second digital device in the group of digital devices hosts the requested service based on the network address; and

in response to the second digital device hosting the requested service, redirecting, by the first digital device, the request to the second digital device.

20. The method of claim 19, further comprising:

receiving, by the first digital device, a periodical message comprising the network address, wherein the periodical message indicates that the second digital device hosts the service associated with the request; and

storing, at the first digital device, the network address in the received periodical message and the service associated with the network address.

21. The method of claim 19, wherein a third digital device in the one or more digital devices is elected as a new host for the service in response to the second digital device stopping hosting the service.

22. The method of claim 21, wherein the third digital device in lieu of the second digital device is associated with the network address when hosting the service.

23. The method of claim 19, wherein the network address comprises a static Internet Protocol (IP) address.

24. The method of claim 19, wherein the one or more digital devices comprises access points that are not coupled to any network device having capabilities of a controller, and wherein the service comprises one or more controller functionalities.

25. A digital device in the group of digital devices, the digital device comprising:

a processor;

a memory;

a listening mechanism operating with the processor, the listening mechanism to listen for a periodical message identifying a service, wherein the service is to be hosted by one or more digital devices in the group of digital devices, wherein the service is associated with a static network address shared by the one or more digital devices, and wherein the periodical message comprises the static network address;

a storing mechanism coupled to the memory, the storing mechanism to store the static network address associated with the service at the first digital device in response to the periodical message being received by the first digital device; and

a determining mechanism operating with the processor, the determining mechanism to determine that no digital device in the one or more digital devices is hosting the service in response to no periodical message being received by the first digital device within a predetermined time period.

26. The digital device of claim 25, wherein a second digital device in the one or more digital devices starts hosting the service after a first digital device in the one or more digital devices stops hosting the service, thereby allowing the first digital device and the second digital device to jointly provide continuous service for clients.

27. The digital device of claim 26, wherein the second digital device is elected as a host for the service based on one or more of the following factors:

a capability of the second digital device;

a capacity of the second digital device;

a classification associated with the second digital device;

a function of the service;

an operating history of the second digital device;

an identifier associated with the second digital device; and

28. The digital device of claim 27, wherein each of the one or more digital devices uses same factors to elect the host for the service.

29. The digital device of claim 25, wherein the static network address comprises a fixed Internet Protocol (IP) address.

30. The digital device of claim 25, wherein the one or more digital devices comprises access points that are not coupled to any network device having capabilities of a controller, and wherein the service comprises one or more controller functionalities.

31. The digital device of claim 25, wherein a plurality of services are distributed across the one or more digital devices that host the services.

32. A digital device in a group of digital devices, the digital device comprising:

a processor;

a memory;

a receiving mechanism operating with the processor, the receiving mechanism to receive a request for a service hosted by one or more digital devices in the group of digital devices, wherein the request comprises a network address corresponding to the requested service;

a determining mechanism operating with the processor, the determining mechanism to determine whether a second digital device in the group of digital devices hosts the requested service based on the network address; and

a redirecting mechanism operating with the processor, the redirecting mechanism to redirect the request to the second digital device in response to the second digital device hosting the requested service.

33. The digital device of claim 32,

wherein the receiving mechanism further receives a periodical message comprising the network address, wherein the periodical message indicates that the second digital device hosts the service associated with the request; and

wherein the digital device further comprises a storing mechanism coupled to the memory, the storing mechanism to store the network address in the received periodical message and the service associated with the network address.

34. The digital device of claim 32, wherein a third digital device in the one or more digital devices is elected as a new host for the service in response to the second digital device stopping hosting the service.

35. The digital device of claim 34, wherein the third digital device in lieu of the second digital device is associated with the network address when hosting the service.

36. The digital device of claim 32, wherein the network address comprises a static Internet Protocol (IP) address.

37. The digital device of claim 32, wherein the one or more digital devices comprises access points that are not coupled to any network device having capabilities of a controller, and wherein the service comprises one or more controller functionalities.