I DATA PORTS 162 I I T I I

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1 L L i _ > A W _ i _ A 7 i L L US A1 (19) United States (12) Patent Appication Pubication (10) Pub. No.: US 2004/ A1 Larsen et a. (43) Pub. Date: (54) NETWORK SWTCH ASSEMBLY, NETWORK SWTCHNG DEVCE, AND METHOD (76) nventors: Loren D. Larsen, Veradae, WA (US); Danie K. Mechior, Cheney, WA (US); Steven R. Ramberg, Veradae, WA (US); Jennifer A. Smith, Veradae, WA (Us) (21) (22) Correspondence Address: WELLS ST. JOHN RS. 601 W. FRST AVENUE, SUTE 1300 SPOKANE, WA (US) App. No.: 10/236,548 Fied: Sep. 5, 2002 Pubication Cassi?cation (51) nt. C?..... H04L 1/00 (52) U.S. c /216 (57) ABSTRACT A network switch assemby incudes a?rst contro entity, a second contro entity, and at east one ine bade. The?rst contro entity is seectivey con?gurabe between an active state and a standby state. The second contro entity is seectivey con?gurabe between a standby state and an active state. The at east one ine bade communicates with at east one of the?rst contro entity and the second contro entity and has at east one port con?gurabe to enabe switching of information. One of the contro entities is con?gured as an active contro entity and another of the contro entities is con?gured as a standby contro entity. The active contro entity is con?gured to transfer state informa tion for the active contro entity that is forwarded to the standby contro entity. A method is aso provided for ren dering contro. //16 OHASS/S 20 i CONTROL ENTTY (CONTROL BLADE) */ K ******* - ju: OONTROL ENTTY (CONTROL BLADE) 4/ 26 DATABASE 53 DATABASE 67 (DATA TABLE) / 5_2 (DATA TABLE) M.52 OPERA T/NO STA TE 11 OPERA T/NO STA TE Z PROTOOOL STA TE _7 _ PROTOOOL STATE L5 SW/TCH/NG MANAOER 5_4 Sw/TOH/NO MANAGER 6_8 MANAGER 2 NANAOER Z2 PROTOCOL STA TE MACH/NE PROTOCOL STA TE MACH/NE / 55 A r44 72 P 56 [34 < < > W 28 v [a \ L/NE BLADE * L/NE BLADE L/NE BLAOE '42 DATA PORTS 162 T ETHERNET PORT 40 k12 : f \\ 70 SW/TCH/NG AOENT fag : _ i i i _ ix i _ k _i J AOENT \ggo TRANSM/T OuEuE \_ 92\~\,5 i

2 1 Patent Appication Pubication Sheet 1 0f 5 US 2004/ A1 / 76,4 78 P "A if)! "ii i CHASSS 20 /' 22 : CONTROL ENT/TY 24 CONTROL ENTTY 25 } (GONTROL BLABE) 4/ (GONTROL BLAOE) 4/ : 1 /46 /-48 /50 [60 [62 /64 \ 1 CPU MEM 514/ CPU MEM 5w i i L DATABASE 53 DATABASE 67. i { (DA TA TABLE) / 5_2 (BA TA TABLE) 4/.62 } OPERA T/NG STA TE 11 OPERA T/NG STA TE & i 1 PROTOGOL STATE Z2 PROTOGOL STA TE 7_8 1 ' ' : SWTCHNG MANAGER 2 SWTCHNG MANAGER Q i E MANAGER 7_0 i : PROTOGOL sta TE MACH/NE PROTOGOL STA TE MAGH/NE 1 L / : A 72 / 36 )/ 34 < <\ k } \ \ E #30 P32 L/NE BLAOE 28 / Y / L/NE BLADE L/NE BLADE DA TA PORTS 5 ETHERNET PORT 40 K72 : SW/TCH/NG AGENT \*88 ; AGENT \\~90 TRANsM/T OuEuE _ 9% 18 1

3 Patent Appication Pubication Sheet 2 0f 5 US 2004/ A SWTCHNG STA TE/DA TABASE 54/ MANAGER YNCHRON/ZA T/ON RE DUNDANGY MANAGER 68 R [26 SWTCHNG MANAGER MANAGER 56 REDUNDANGY 90/ AGENT SWTCHNG AGENT 28 E1 HE 70 7 q \ SWTCHNG 54 // MANAGER 55 RE DUNDANGY 55 / MANAGER 70 SWTCHNG MANAGER MANAGER 28 RE DUNDANGY 90/ AGENT SW/ TGH/NG 55/ AGENT

4 Patent Appication Pubication Sheet 3 0f 5 US 2004/ A1 70 \ \ SWTCHNG GONE/G : SWTCHNG 54 MANAGER SYNCHRON/ZA T/0N MANAGER MANAGER 70 / MANAGER 28 AGENT 90.2 JL E if SWTCHNG 88 AGENT \7 \ ~ sw/tgh/ng CONF/G r SYNCHRON/ZA T/0N SWTCHNG 64 MANAGER PROTOCOL V MANAGER \ 68 SYNCHRON/ZA MON 56 MANAGER 7OJ/ MANAGER #28 \ AGENT 90 SWTCHNG F 5 88 / AGENT i.

5 Patent Appication Pubication Sheet 4 0f 5 US 2004/ A1 511 i \ : 24 A 26 Sw/TGH/NG SW/TGH/NG 54/ MANAGER 68/ MANAGER 5:m 1 3:, 1 5.'m1 ' 2:m1 5.'m 7-ACK 2'9 90 AGENT "m 2 E Sw/TGH/NG 88 AGENT \_ SW/TGH/NG MANAGERS LB-x? 94 SWTCHNG MANAGERS 54 '7 r56 68d r70 r4 '7, 5 MANAGER L MANAGER r1 * 24 r7 \ \ J 90 AGENT 28 7:017 SW/TGH/NG E 1- g '1 88/ AGENTS 96

6 Patent Appication Pubication Sheet 5 0f 5 US 2004/ A1 ( START ) r \ PROV/DE WETWORK SWTCH/NC DEV/CE W/TH ACT/VE CONTROL ENT/TY, STANDBY CONTROL ENT/TY, AND L/NE BLADE(S) 157 WTH PLURAL/TY OF DATA PORTS CONNECTED WTH SW/TCH/NG FABR/C DETECT OPERATNG STATE OF ACT/VE CONTROL ENT/TY 52 GENERA TE PARAMUER(S) ND/CA T/VE 1 OF OPERA TNG STA TE 55 TRANSFER PARAMETER(S) FROM ACT/VE CONTROL ENT/TY TO 154 STANDBY CONTROL ENT/TY SYNCHRON/ZE STATE OF ACT/VE CONTROL ENT/TY W/TH STATE OF STANDBY CONTROL ENT/TY "55 USNG PARAMETER(S) DETECT FALURE OF ACT/VE 1 CONTROL ENTTY 55 CONVERT STANDBY CONTROL ENT/TY NTO NEW ACT/VE CONTROL ENT/TY 57

7 NETWORK SWTCH ASSEMBLY, NETWORK SWTCHNG DEVCE, AND METHOD TECHNCAL FELD [0001] This invention pertains to switching of packets in packet switched systems. More particuary, this invention reates to a switch assemby having at east two contro entities, or contro bades, Wherein the contro bades are aternatey con?gured as an active contro bade and a standby contro bade, respectivey, to enabe reativey high speed switchover to the standby contro bade When a faiure or error condition is detected invoving the active contro bade. BACKGROUND OF THE NVENTON [0002] One previousy known switching technique pro vides a device having the abiity for a standby contro entity to read the con?guration of an active contro entity and perform a soft reboot, or software reoad and restart, if something happens to the active contro entity. Other devices provide for a true hot-standby, Where a backup contro entity is ready to take over for the active contro entity. HoWever, these devices are not operating using dynamic earning or protocos. Rather, they provide staticay con?gured circuits. For exampe, permanent virtua circuits have previousy been impemented in an Asynchronous Transfer Mode (ATM) switching device. Accordingy, an improved switch ing device and method are needed to enabe improved switchover to a new active contro entity With a reativey sma switchover time. SUMMARY OF THE NVENTON [0003] A network switch assemby is provided With an active contro entity and a passive contro entity that are aternatey con?gured as an active contro entity and a standby contro entity to impart redundancy functionaity to a switching device using a synchronization process between the contro entities to reduce switchover time and accuracy. n one case, the network switch assemby is an Ethernet switch assemby, and each contro entity comprises a contro bade. [0004] According to one aspect, a network switch assem by incudes a?rst contro entity, a second contro entity, and at east one ine bade. The?rst contro entity is seectivey con?gurabe between an active state and a standby state. The second contro entity is seectivey con?gurabe between a standby state and an active state. The at east one ine bade communicates With at east one of the?rst contro entity and the second contro entity and has at east one port con?g urabe to enabe switching of information. One of the contro entities is con?gured as an active contro entity and another of the contro entities is con?gured as a standby contro entity. The active contro entity is con?gured to transfer state information for the active contro entity that is forwarded to the standby contro entity. [0005] According to another aspect, a network switching device incudes a pair of contro entities and at east one ine bade. The pair of contro entities each have processing circuitry. Each contro entity is seectivey con?gurabe between an active state and a standby state in an aternating manner. More particuary, one contro entity is con?gured in an active state Whie another contro entity is con?gured in a standby state. The at east one ine bade communicates With the?rst contro entity and the second contro entity. The at east one ine bade has a switching agent and a redun dancy agent. The processing circuitry from the?rst contro entity communicates With processing circuitry from the second contro entity. One of the contro entities is con?g ured as an active contro entity and another of the contro entities is con?gured as a standby contro entity. Further more, one of the processing circuitry is con?gured to trans fer a state of the active contro entity to the standby contro entity. [0006] According to yet another aspect, a network switch ing device incudes?rst contro means, second contro means, and ine bade means. The?rst contro means is provided for con?guring the switching device and is seec tivey con?gurabe between an active state and a standby state. The second contro means is provided for con?guring the switching device and is seectivey con?gurabe between a standby state and an active state. The ine bade means is provided for enabing switching information between ports and communicating With at east one of the?rst contro entity and the second contro entity. One of the?rst contro means and the second contro means is con?gured as an active contro entity, another of the?rst contro means and the second contro means is con?gured as a standby contro entity, and the active contro entity is con?gured to transfer state information for the active contro entity that is for Warded to the standby contro entity. [0007] According to even another aspect, a method is provided for rendering contro entity redundancy in a net Work switching device. The method incudes: providing a network switching device incuding a?rst contro entity in an active state, a second contro entity in a standby state, and at east one ine bade communicating With the?rst and second contro entities and having a puraity of data ports interconnected via switching fabric; detecting an operating state of the active contro entity; generating at east one parameter indicative of the detected operating state; and transferring the at east one parameter from the active contro entity to the standby contro entity. [0008] One advantage provided by the present invention is the abiity to bring a standby contro entity up to a synchro nized state With an active contro entity. Another advantage is to maintain the synchronized state on an ongoing basis. A third advantage is to detect faiure of the active contro bade and transfer contro to the standby contro bade in a reativey short amount of time. Even another advantage is to provide one or more of the above advantages Whie aso maintaining the abiity to determine Which of the contro bades is active and Which of the contro bades is on standby. BREF DESCRPTON OF THE DRAWNGS [0009] Preferred embodiments of the invention are described beow With reference to the foowing accompa nying drawings. [0010] FG. 1 iustrates a bock diagram overview of an exempary basic system con?guration for network switching utiizing redundant contro entities, according to one embodiment of the present invention. [0011] FG. 2 iustrates a passive backup redundancy mode impementation for the system of FG. 1.

8 [0012] FG. 3 iustrates an active-protected redundancy mode impementation for the system of FG. 1. [0013] FG. 4 iustrates a distributed state redundancy mode impementation for the system of FG. 1. [0014] FG. 5 iustrates a hybrid redundancy mode impementation for the system of FG. 1. [0015] FG. 6 iustrates a modi?ed active-protected redundancy mode impementation for the system of FG. 1. [0016] FG. 7 iustrates a standby signa queue for the modi?ed active-protected redundancy mode of FG. 6. [0017] FG. 8 is a process How diagram showing the process stages for impementing contro redundancy in a network switching device by way of the system of FGS DETALED DESCRPTON OF THE PREFERRED EMBODMENTS [0018] This discosure of the invention is submitted in furtherance of the constitutiona purposes of the US. Patent Laws to promote the progress of science and usefu arts (Artice 1, Section 8). [0019] Reference wi now be made to a preferred embodi ment of Appicant s invention. An exempary impementa tion is described beow and depicted with reference to the drawings comprising a network switch assemby system that uses two contro bades such that one contro bade is active and another contro bade is on standby. Whie the invention is described by way of a preferred embodiment, it is under stood that the description is not intended to imit the inven tion to such embodiment. nstead it is intended to cover aternatives, equivaents, and modi?cations which may be broader than the embodiment, but which are incuded within the scope of the appended caims. [0020] n an effort to prevent obscuring the invention at hand, ony detais germane to impementing the invention wi be described in great detai, with presenty understood periphera detais being incorporated by reference, as needed, as being presenty understood in the art. [0021] 1. Terminoogy Speci?c to Network Switching [0022] Bade As used herein, the term bade refers to the components mounted within a chassis of a data switch ing device, such as an Ethernet switch. Numerous eectronic devices are mounted on the bades, within the chassis of the data switching device. Typicay, bades are swapped out from the chassis, depending on the particuar needs pre sented by the switching environment in which the data switching device has been paced. [0023] Contro bade The term contro bade refers to a bade that incudes a microprocessor and maintains con?guration information in a database. The contro bade aso maintains dynamic system information incuding Layer 2 forwarding databases, protoco state machines, and the operationa status of ports within the system. Acontro bade imparts contro functioning and acts as a master reative to a ine bade, which acts as a servant. [0024] Line Bade The term ine bade as used herein refers to a bade that incudes data ports, such as Ethernet ports, that are interconnected via a switching fabric in order to enabe data traffic to be switched between such ports. n association with a contro bade, the ine bade takes on the reationship of a servant. [0025] Switching Fabric As used herein, the term switching fabric refers to a combination of hardware and software that moves data coming into a network node out by the correct port (door) to the next node within the network. Switching fabric incudes switching units, or individua boxes, in a node; integrated circuits contained in the switch ing units; and programming that aows switching paths to be controed. The term switching fabric is aso intended to mean coectivey a switching hardware and software in a network. The term appears to use a metaphor for textie weaving in order to suggest the compexity and web-ike structure of switching paths and ports within a node. The Signa Computing System Architecture (SCSA) which serves to provide a mode framework for computer tee phony, uses this term. Within the SCSA framework, a portion of the hardware mode incudes a Switch Fabric Controer. Asynchronous transfer mode (ATM) and frame reay are sometimes referred to as switching fabric tech noogies. t is understood that switching fabric typicay incudes data buffers and the use of a shared memory. [0026] 2. System Leve Overview [0027] FG. 1 iustrates a network switch assemby sys tem identi?ed by reference numera 10. By way of one exampe, network switch assemby comprises an Ethernet data switching device, or Ethernet switch, 12 provided within a network environment 14. Ethernet switch 12 incudes a chassis 16 that carries eectronic devices 18, incuding a pair of contro entities 20 and 22 that are seectivey and aternatey con?gured between an active state and a standby state. More particuary, in one case each contro entity 20 and 22 comprises a contro bade 24 and 26, respectivey. Additionay, switch 12 incudes a number of ine bades, such as ine bades 28, 30 and 32 that are couped together with contro bades 24 and 26 via a communication medium 34, such as a high speed bus in the form of a back pane 36. [0028] Line bades 28, 30 and 32 each incude a puraity of data ports 38, such as Ethernet ports 40. Athough they have been simpi?ed for the drawing, ine bades 30 and 32 incude the interna eements shown in ine bade 28. Ports 38 are interconnected with a switching fabric 42 in a manner that enabes data traf?c 44 to be switched between ports 38 in a desired manner. [0029] According to FG. 1, contro bade 24 incudes a centra processing unit (CPU) 46, memory 48, contro software (SW) 50, a database 52, a switching manager 54, a redundancy manager 56 and a protoco state machine 58. Likewise, contro bade 26 incudes a CPU 60, memory 62, contro software (SW) 64, a database 66, a switching man ager 68, a redundancy manager 70, and a protoco state machine 72. [0030] Databases 52 and 66 are con?gured to record the operating state 74 of contro entity 20, when contro entity 20 is the active contro entity. Likewise, databases 52 and 66 each record the operating state 74 of contro entity 22, when contro entity 22 is the active contro entity. Contro entities 20 and 22 aso incude the protoco state 78 of the active contro entities 20 and 22 within operating state 74. Protoco state 78 is derived from protoco state machines 58 and 72, respectivey.

9 [0031] More particuary, CPUs 46 and 60 each comprise a microprocessor. Databases 52 and 66 are used to maintain con?guration information, as We as maintain dynamic system information, such as Layer 2 forwarding databases, protoco state machines, and the operationa state (or status) of ports 38 in system 10. t is understood that mutipe protocos are typicay operating, With each protoco having one or more state machines associated With the respective protoco. [0032] System 10 uses two contro entities 20, 22 (or contro bades 24, 26) in a manner that maintains one contro bade as an active contro bade and the other contro bade as a standby contro bade. f a faiure is detected on the active contro bade, the standby contro bade is used to assume operating responsibiities from the active contro bade, thereby becoming the new active contro bade and taking over management of system 10. The od active contro bade then becomes the new standby contro bade, assuming that it is sti operating. The preceding assumes that the faiure that initiated this process Was a faiure of the active contro bade. t is desirabe to maintain as sma a time as possibe between any faiure of the active contro bade and switchover of contro to the standby contro bade, making it the new active contro bade. [0033] According to system 10 of FG. 1, there are two main aspects that contribute to reaizing a desired, reativey sma switchover time. First, a particuar mechanism is used by system 10 to synchronize the state of the contro bades 24, 26 and keep the states synchronized over time. Secondy, system 10 uses a particuar mechanism for detecting a faiure and maintaining synchronization. [0034] Upon start-up of system 10, one of contro bades 24 and 26 is designated as the active contro bade. For exampe, upon start-up, contro bade 24 can be designated as the active contro bade. f there is another contro bade at the time of start-up, the other contro bade is designated as the standby contro bade (contro bade 26, in the exampe). HoWever, for the case Where the other contro bade is inserted into system 10 foowing power-up of system 10, it is designated as the standby contro bade in response to inserting the other contro bade. [0035] Once a contro bade has been designated as a standby contro bade, the contro bade needs to be syn chronized With the active contro bade using a particuar synchronization process described beow in greater detai. The synchronization process requires that the state on the active contro bade be transferred to the standby contro bade. The state is typicay kept in a database, in an appropriate database format. The synchronization process transfers the contents of the database from the active contro entity to the standby contro entity. For exampe, for the case Where contro bade 24 is active and contro bade 26 is in a standby mode, contents of database 52 are transferred to database 66. Any state that is present outside of the database is transferred via messages Within system 10. [0036] When synchronizing, one important factor is the abiity to queue the inputs to the active contro bade, transfer the state, and then process the inputs that Were previousy queued, a Without osing information even though queuing of the inputs causes a state change. Once the contro bades have been synchronized With the same state, if the processors on both contro bades have identica hardware con?gurations and run identica versions of soft Ware, then identica inputs Wi produce identica states in such contro bades. [0037] State changes on a contro bade 24 can be pro vided by two sources. First, state changes can be generated by an interna protoco operation. Secondy, state changes can be generated as inputs from the ine bade 28. The inputs may consist of management commands, such as in the form of Command Line nterface (CL) commands that are gen erated over a tenet session, or via a management protoco, such as via Simpe NetWork Management Protoco (SNMP), as We as via protoco contro packets. [0038] n the?rst case, if the protocos are synchronized, using the protoco given in the above exampe, and they receive substantiay identica input, then they shoud remain synchronized. n the second case, if the management com mands and contro protoco packets are processed substan tiay identicay on the processors running substantiay identica code With substantiay identica con?guration, then they shoud aso produce an identica state change on each processor. As used herein, the term substantiay identica refers to suf?cienty identica to produce identica responses to ine bades based on equivaent inputs. [0039] For purposes of understanding the design ayout, network switch assemby 10 of FG. 1 has been described in genera terms With respect to the manner in Which redundancy management is carried out for contro entities 20 and 22. HoWever, it is understood that mutipe unique product con?gurations (or modes) are possibe for network switch assemby 10. Such mutipe unique product con?gu rations resut in mutipe unique switching products, each optimized for a speci?c set of operating parameters and requirements. Accordingy,?ve unique product con?gura tions Wi be described in greater detai beow for reaizing contro bade redundancy. Techniques for synchronizing contro bades Wi aso be described. [0040] 3. Contro Bade Redundancy [0041] With respect to redundancy functionaity in net Work switching products that take on the con?guration of network switch assemby 10 of FG. 1, it is understood that not a products Wi support a of the redundancy features that Wi be described beow. [0042] Contro bade redundancy is reaized using?ve unique product con?gurations that resut in?ve modes of redundancy. Contro bade redundancy requires that contro bades, or contro entities, back each other up With an identica con?guration. Accordingy, if one modue, contain ing a contro bade, fais or becomes unheathy, the standby modue, containing the other contro bade, becomes active and traffic switches to the ports of the new active modue. n order to ensure smooth operation, it is desirabe for the switchover time to be ess than 500 miiseconds, according to one impementation. [0043] There are?ve modes of redundancy that are used as a basis for the present switching redundancy architecture: a Passive-Backup Mode; an Active-Protected Mode; a Distributed State Mode; a Hybrid Mode; and a Modi?ed Active-Protected Mode. Each mode has advantages and disadvantages that make utiization of one mode more suitabe than the others for a particuar set of operating conditions and system environment.

10 [0044] For purposes of this discosure, a system is said to be in Protected Mode if the standby contro is in such a state that, if the active contro bade Were to fai, it coud become the active contro bade Without incurring a oss of system state. [0045] 3.1 Passive-Backup Mode [0046] FG. 1 iustrates the Passive-Backup Mode 11 of redundancy impemented via the network switch assemby 10 (of FG. 1). According to the Passive-Backup Mode 11, redundancy agent 90 from each ine bade 28 communicates ony With active contro bade 24. Active contro bade 24 is responsibe for maintaining the state of standby contro bade 26. Contro bades 24 and 26 each incude switching managers 54 and 68 and redundancy managers 56 and 70, respectivey. Line bade 28 incudes a redundancy agent 90 and a switching agent 88. [0047] There are severa techniques used to reaize this communication arrangement. HoWever, the genera approach is common in that the active contro bade 24 sends an updated state or updated database periodicay to the standby contro bade 26. [0048] HoWever, there are severa probems With using the Passive-Backup Mode over other aternative modes described herein. First, impementation of this mode adds additiona burden on the active contro bade as the active contro bade is required to constanty send state updates to the standby contro bade. This coud negativey impact overa performance. For instance, this coud adversey affect the abiity of the system to hande nternet Group Management Protoco (GMP) channe changes. Since the database is aready overburdened and is considered a point of congestion (or choke point), requiring it to further dupi cate each signa and send it to the standby contro bade may increase restriction of the choke point even further. [0049] Secondy, there is a need to reconcie ine bade state With contro bade state. A changes on the active contro bade are sent to the standby contro bade. There fore, if the active contro bade fais and has severa signas on its queue, then the standby contro bade Wi be out of synchronization With the ine bades. There is no abiity to verify ine bade state With contro bade state. [0050] There are severa identi?ed advantages to using the Passive-Backup Mode over other aternative modes described herein. First, it provides a reduced compexity approach, reative to the other approaches. Secondy, it provides a reativey fast switchover time, ignoring any ost active signas and requirements to correct out of synchro nization ine bades. [0051] 3.2 Active-Protected Mode [0052] FG. 3 iustrates an Active-Protected Mode 111 of redundancy for the network switch assemby 10 (of FG. 1). The Active-Protected Mode 111 assumes that the standby contro bade 26 maintains the exact state of the active contro bade 24 at a times. Therefore, if the active contro bade 24 fais, the standby contro bade 26 can take over Without requiring state synchronization. [0053] There are severa Ways to impement the Active Protected Mode 111 of redundancy for contro bades. The genera approach taken for the present switching design assumes that the state of a redundancy agent 90 is totay predictabe by observing the messages sent to it by redun dancy manager 56. And ikewise the states of the redun dancy managers 56 and 70 are totay predicabe as ong as the same messages are received in the same order from redundancy agents 90. This is true for an initia synchroni Zation or a simutaneous boot using the same initia con?guration. For exampe, the spanning tree port state of any given port can aways be determined by observing the message sent to the port by the port s manager. This means that by merey repicating messages sent from redundancy agent 90 to managers 56 and 70 on an active contro bade 24 and a standby contro bade 26, respectivey, the manager states Wi be the same and the agent states Wi be known by both managers 56 and 70. [0054] More particuary, FG. 3 iustrates a setup With two contro bades 24 and 26 taking to a singe ine bade 28. The managers 56 and 70 on both the active and standby contro bades 24 and 26 receive the same signas from the agent 90 (and agent 88) and process the signas in the same Way. Redundancy agent 90 dupicates a signas destined for the active contro bade 24 and sends them to the standby contro bade 26. [0055] HoWever, any signas from the redundancy man ager 56 ony come from the active contro bade 24. The redundancy manager 70 of the standby contro bade 26 drops a messages to the redundancy agent 90 since this message Woud be a dupicate of What the active contro bade 24 has aready sent to ine bade 28. [0056] f contro bades 24 and 26 are not booted together, then some method is required to initiay synchronize the contro bades. The Passive-Backup Mode (of FG. 2) can be impemented and used in order to provide an initia synchronization between the contro bades 24 and 26 Where they are not booted together. [0057] There exist severa disadvantages to using the Active-Protected Mode. First, the Active-Protected Mode requires the use of another synchronization method for initiaization. For exampe, it may require use of the syn chronization method used in the Passive-Backup Mode. When contro bades are not booted together, it is necessary to use the Passive-Backup Mode synchronization mecha nism to synchronize the contro bades initiay. Each time the contro bade drops out of protected mode, then it must stop a contro bade/ine bade traf?c, resynchronize and then resume. [0058] Secondy, the Active-Protected Mode uses a rea tivey ess compicated design and one over Which there is not a ot of contro, nor is there an abiity to correct if there are probems. [0059] Thirdy, the Active-Protected Mode assumes that the state of the system is deterministic based on the receipt of signas. That is, the signas coming in from the agents must be received in the same order by both contro bades. This is the key to the mode s success. HoWever, there are severa scenarios in Which this Wi not occur. The most obvious scenario occurs With inputs from the oca port on the contro bade. Ceary, athough these signas can be repicated and sent to the standby contro bade, there are situations in Which they Wi not be received in the same order. Additionay, the oading on each contro bade is not the same, so that processing of the signas may be different for each bade Which may ead to non-deterministic behav ior.

11 [0060] Fourth, the Active-Protected Mode aso requires that the system be abe to synchronize itsef Whie running. There are many cases in Which the system coud fa out of protected mode. For instance, if a ine bade oses a ink With ony one of the contro bades, the system is no onger protected since signas are ony going to one contro bade. Thus, the active contro bade is required to now run in a non-protected synchronizing mode unti the ink is re estabished. Once it is re-estabished, then the system can re-synchronize and go back into protected mode, as dis cussed previousy. [0061] Fifth, With the Active-Protected Mode, during a switchover, it is possibe for the managers and agents to become out of synchronization due to the oss of signas. There are a coupe of situations in Which this coud occur. HoWever, the situation during a faiure of the active contro bade is most recognizabe. n this scenario, the active contro bade has faied. HoWever, there are severa signa messages sti on the active contro bade s queue that need to be sent. Obviousy, they are ost on the active contro bade. HoWever, the standby bade Wi continue to dump its signas unti it has detected a faiure. Since detection does not happen immediatey, the potentia for ost signa responses from the managers is not insigni?cant. As a resut of such an occurrence, the managers on the standby bade Wi be out of synchronization With the ine bades once the standby contro bade becomes the new active contro bade. [0062] Sixth, With the Active-Protected Mode, a oss of signas between a ine bade and a contro bade can cause a oss of synchronization between the active and standby contro bades. Use of a reiabe transport mechanism can guarantee the signa deivery. HoWever, this can introduce errors. For instance, assume two ine bades send signas to both contro bades. f one signa needs to be retransmitted, then it is possibe that the contro bades Wi receive the signas in a reverse order, thus causing a synchronization probem. [0063] Seventh, With the Active-Protected Mode, severa managers are state machines driven by timers. These timers cannot be synchronized between contro bades. Therefore, for exampe, the state of EEE 802.1W Rapid Spanning Tree Protoco (RSTP) Wi never be the same on both contro bades. The impact on state synchronization is not reay known. [0064] Eighth, With the Active-Protected Mode, it is pres enty beieved to be impossibe to verify that the states are synchronized uness a traffic to the contro bades is stopped. [0065] Ninth, With the Active-Protected Mode, there is no mechanism to verify that the ine bade states are in syn chronization With the contro bades. Furthermore, there is no mechanism to cean up entries. [0066] Tenth, With the Active-Protected Mode, memory eaks Wi typicay be re?ected on both the active and standby contro bades since they are running in parae. Therefore, this approach does not protect against software faiures that manifest as memory eaks. [0067] There exist severa advantages to using the Active Protected Mode. First, the Active-Protected Mode has the fastest switchover time of the modes described herein, ignoring any time required to synchronize ine bades due to signas ost on the active contro bade. [0068] Secondy, the Active-Protected Mode paces mini ma oading on the active contro bade due to redundancy. [0069] There exist other considerations With an Active Protected Mode. Namey, the procedure for a software upgrade occurs as foows: Drop out of protected mode; (ii) upgrade the standby contro bade software and aow it to reboot; (iii) resynchronize the active and standby contro bades; (iv) switch over to the standby contro bade; (v) upgrade the other former active contro bade and reboot it; and (vi) synchronize the contro bades and aow the od standby contro bade to remain the active contro bade and go into protected mode. [0070] The probem With the above-described approach ies in procedure (iii), above, because it requires use of different versions of contro bade software to synchronize the active and standby contro bades. n some cases, it may not be possibe to synchronize between the two different versions of software. Athough this can be incorporated as a requirement for any software upgrades, the ony requirement is that the contro bade software shoud be compatibe With the current ine bade software. Accordingy, different soft Ware versions shoud be abe to synchronize themseves. n this case, synchronization does not necessariy mean being abe to run in parae. [0071] 3.3 Distributed State Mode [0072] FG. 4 iustrates a Distributed State Mode 211 of redundancy for the network switch assemby 10 of FG. 1. The Distributed State Redundancy Mode assumes that the manager state can be re-created by the state stored on each of the ine bades 28. n this mode, the ine bades 28 send signas ony to the active contro bade 24. The standby contro bade 26 is running in a standby mode in Which it Wi update con?guration changes, but Wi not act upon them. [0073] f the active contro bade 24 fais, the standby contro bade 26 takes over. On oss of connection to the active contro bade 24, the redundancy agent 90 on each of the ine bades Wi queue any incoming signas. Once the standby contro bade 26 has become active, the switching manager 68 on the standby contro bade 26 Wi send a synchronization request to the ine bades 28. Each of the redundancy agents 90 Wi then send their state data via a specia Appication Program nterface (AP) since the redun dancy agents 90 are queuing a reguar traf?c. [0074] Each switching manager 54 and 68 is responsibe for being abe to recreate its database given information from its agent. Each switching manager 54 and 68 can do so independent of the order in Which information is received. n most cases, this Wi mean that each redundancy agent 90 has a subset of the manager database tabe (tabes 53 and 67 of FG. 1). When a resynchronization is required, the redun dancy agent 90 Wi send the switching manager 54 or 68 its tabe entries and the switching manager 54 or 68 Wi consoidate them into its tabe. [0075] Once the synchronization is compete, the redun dancy manager 56 or 70 tes the redundancy agent 88 to start sending signas.

12 [0076] n the case of con?guration changes, it is required that the active contro bade con?guration be synchronized With that of the standby contro bade. Thus, the active and standby contro bades sti perform some background syn chronization for user con?guration changes. [0077] There exist severa disadvantages to using the Distributed State Redundancy Mode. First, agent design is impacted greaty as agents are now required to store their state. n addition, the managers may need to transfer down unnecessary data that needs to be stored by the ine bades. t aso may require that the agents use the database that they do not currenty use. t may aso mean that drivers may need to be modi?ed to provide state information (i.e., get cmds). [0078] Secondy, for arge tabes the synchronization pro cess coud be sow. As a resut, a desired faiover time coud be adversey affected. A detection and switchover can occur in that time. HoWever, it may take severa seconds after that to competey regenerate the state. n this amount of time, packets Wi continue to be switched through the switching fabric, athough no new packet processing can be done by the contro entity. [0079] There exist severa advantages to using the Dis tributed State Redundancy Mode. First, it is abe to re create manager state at any time. Thus, it is not impacted by oss of signas on the active contro bade. [0080] Secondy, there is minima additiona oading on the active contro bade due to redundancy. [0081] Thirdy, it is robust. A manager can synchronize at any time and has more knowedge of the actua state of the agent. [0082] Fourth, managers/protocos Without agents cannot be synchronized by the ine bades and thus need to be restarted on the standby bade When it becomes active. [0083] Fifth, it may not meet switchover criteria since there is a considerabe amount of data to synchronize from the ine bades. [0084] 3.4 Hybrid Mode [0085] FG. 5 iustrates the Hybrid Mode 311 of redun dancy for the network switch assemby 10 of FG. 1. The Hybrid Mode 311 is a merging of seected design features from the Passive-Backup and Distributed State Modes that combine to overcome the de?ciencies individuay in each of these modes. The major probem With the Distributed State Mode is that protocos running ony on the managers cannot be synchronized. The probem With the Passive-Backup Mode is that there is a WindoW during faiover in Which signas are dropped Which can cause managers to be out of synchronization With the ine bades. [0086] More particuary, the Hybrid Mode 311 provides for con?guration synchronization and protoco synchroni Zation of the switching managers 68 of the standby contro bade 26 from the switching managers 54 of the active contro bade 24. The redundancy agent 90 of an active ine bade 28 communicates bi-directionay With the redundancy manager 56 of the active contro bade 24. [0087] The Hybrid Mode 311 makes the foowing assumptions When trying to correct for these de?ciencies: [0088] First, protocos are ess susceptibe to oss of signa synchronization information and can recover over time Without the need of information from the ine bades 28. [0089] Secondy, the managers 54, 56 need to synchronize With the ine bades 28. There Wi be cases outside of redundancy that this may be needed. [0090] There exist severa advantages to using the Hybrid Mode. First, it aows the managers to synchronize from the state on the ine bades. Thus, no state information is ost. [0091] Secondy, it aows the protocos to synchronize their state to an acceptabe eve from Which they can recover after a switchover. [0092] There exist severa disadvantages to using the Hybrid Mode. First, it is a reativey compicated impe mentation. More particuary, it requires that the agents keep the state of managers. t aso generay requires that a manager on one contro bade knows about and can com municate With its redundant-sef on the standby contro bade. HoWever, this greaty compicates the design. [0093] Secondy, it may not be abe to meet the desired contro bade switchover criteria. n one impementation, the desired contro bade switchover criteria Was a time imit of 0.5 seconds. This is due to the fact that there is a consider abe amount of data from the ine bades that needs to be synchronized by the manager. [0094] 3.5 Modi?ed Active-Protected Mode [0095] FG. 6 iustrates the Modi?ed Active-Protected Mode for the network switch assemby of FG. 1. The Active-Protected Mode (of FG. 3) can be extended in fairy simpe Ways to achieve this modi?cation Which soves most of the disadvantages that Were previousy discussed. First, the approach Wi be described. Then, the manner in Which it soves each of the probems Wi be iustrated. [0096] First, a switching agent 88 sends a message m to a redundancy agent 90 Within a ine bade 28 for transmis sion to a contro bade 24. [0097] Secondy, the redundancy agent 90 forwards mes sage m to the contro bade 24 that appears to be active at the time. [0098] Thirdy, When message m1 is received from the redundancy agent 90 on ine bade (LBx) 28, it is forwarded to the redundancy manager 70 on the standby contro bade 26. [0099] Fourth, When the redundancy manager 70 on the standby contro bade 26 receives the message it is for Warded towards the switching manager 68 on standby con tro bade 26. Additionay, an acknowedgment (m-ack) message is sent back to the redundancy manager 56 on the active contro bade 24. [0100] Fifth, When the redundancy manager 56 on the active contro bade 24 receives the acknowedgment mes sage (m1-ack), it is forwarded to the correct manager 54 on the active contro bade 24 and the acknowedgment mes sage (m1-ack) is forwarded back to the ine bade 28 (LBx). When the redundancy agent 90 on ine bade 28 receives this acknowedgment message (ACK), the redun dancy agent removes the message from its transmit queue. This aows another message to be sent up to the contro bades 24 and 26.

13 [0101] There appear to be four cases Where faiure can occur in the Modi?ed Active-Protected Mode above. m-ack: CBS->CBA m-ack: CBA->LBX CBA fais here CASE 2: m1: LBX >CBA CBA fais here [0102] Case 1 Wi guarantee that the messages Wi arrive at both the active contro bade and the standby contro bade. AfooWing description Wi discuss how to guarantee that the repy messages Wi be returned to the correct ine bade. [0103] Cases 2, 3, and 4 are the same in the sense that the acknowedgment message (m-ack), corresponding to message m1, does not make it back to the ine bade 28 (LBX), meaning that it Wi re-transmit after a timeout period. There is a possibiity in Case 2 and Case 3 that a request Wi be received by the contro bade mutipe times. [0104] For the cases above, centra processing unit (CPU) egress issues become a concern. When state is communi cated from a ine bade to a contro bade and that commu nication produces state changes at the contro bade that must then be sent back down to the ine bade, there needs to be a Way for the contro bade to know that its message Was received at the ine bade. [0105] Using Modi?ed Active-Protected Mode 511 When an active contro bade fais, there is a period of time required for the system to detect the faiure, 6. When the standby contro bade becomes active, the system does not know Which actions required by a ine bade Were competed prior to the faiure, and Which Were never competed. Those operations that Were not competed by the active contro bade need to be propery competed by the standby contro bade in order for the system to operate correcty. [0106] A?rst soution invoves sending an acknowedg ment (ACK) to everything that goes down to the ine bade 28. The probem is then removed. HoWever, there is a risk of osing acknowedgments (ACKs). [0107] A second soution invoves having the redundancy manager 70 on the standby contro bade 26 not drop the messages being sent down. Essentiay, a concept caed a throwaway WindoW is used. The throwaway WindoW is sized by time of a size 6. This 6 vaue may be difficut to correcty size, a priori. One exempary vaue for 6 that is achievabe is 500 miiseconds. HoWever, for some cases, this coud be quite arge. On the other hand, in combination With a the acknowedgments being transmitted, it might be reativey sma. Essentiay, there is a queue in the software arge enough to contain the maximum number of messages that can be sent Within the throwaway WindoW. Once a message is oder than the vaue, then it is discarded. f a faiover occurs, then the standby contro bade just sends a the messages that are queued up in the throwaway candidate queue. [0108] The above-described scheme appears functiona. HoWever, it appears to suffer from a probem in that a given message may arrive at a ine bade mutipe times. The above-described scheme can be extended as shown beow With reference to FG. 7. [0109] FG. 7 iustrates a Modi?ed Active-Protected Mode With Standby Signa Queue 611 for the network switch assemby 10 of FG. 1. Essentiay, When the active contro bade 24 sends its repy message down it aso sends it to the standby contro bade 26. The standby contro bade 26 aso repies in the same order. This assumes that the contro bades 24 and 26 are processing messages in the same sequence. When the standby contro bade 26 gets the repy message, it compares the message With the entry 96 at the head of the queue 94. f the message and the entry 96 match, then the message is de-queued With the assumption that this message has aso arrived at the ine bade 28. [0110] FooWing is a description of how the Modi?ed Active-Protected Mode 611 With Standby Signa Queue of FG. 7 soves the disadvantages previousy described for the Active-Protected Mode. [0111] The?rst identi?ed disadvantage for the Active Protected Mode Was the required use of another synchro nization method for initiaization. HoWever, a approaches (or modes) require some scheme to initiay get in synchro nization. For the FG. 7 approach, it is desirabe to use the distributed state scheme to get initiay in-synchronization. [0112] The second identi?ed disadvantage for the Active Protected Mode Was recognition that it is the most compi cated design, it has imited contro abiity, and it has a imited abiity to correct if there are probems. [0113] The third identi?ed disadvantage for the Active Protected Mode Was that it assumes the state of the system is deterministic based on the receipt of signas. HoWever, this probem appears to be soved in the present mode of FG. 7 by the fact that there is a singe sequentia path between a ine bade and the contro bades. [0114] The fourth identi?ed disadvantage for the Active Protected Mode resuted because the method aso requires that the system be abe to synchronize itsef Whie running. HoWever, this is aways an issue, irrespective of the mode used. f the system oses synchronization, it has to get back in synchronization using the Distributed State Mode tech nique. This Woud aso be true in the current Hybrid Mode. [0115] The?fth identi?ed disadvantage for the Active Protected Mode resuted because, during a switchover, it is possibe for the managers and agents to become out of synchronization due to the oss of signas. The present mode of FG. 7 resoves this disadvantage by queuing at the standby contro bade any messages that may have been sent

14 by the active contro bade Within the WindoW of time required for the standby contro bade to detect a faiure and begin forwarding its own messages. When a faiure is detected the messages in the queue are transmitted prior to any other messages transmitted by the new active contro bade. This eiminates the possibiity that messages queued on the active contro bade destined to the ine bades are ost during faiover detection and faiover. [0116] The sixth identi?ed disadvantage for the Active Protected Mode Was that the oss of signas between ine bades and contro bades can cause a oss of synchroniza tion between the active and standby contro bades. This probem is mitigated now because of the singe point of entry of messages into the contro bade software. t is assumed that messages from ine bades are independent of one another and their reative ordering can be fairy arbi trary. [0117] The seventh identi?ed disadvantage for the Active Protected Mode Was that severa managers are state machines driven by timers, and these timers cannot be synchronized between contro bades, so the state of Rapid Spanning Tree Protoco (RSTP) Wi never be the same on both contro bades. This is an issue With a the modes (or soutions). n some cases, RSTP/LACP can become syn chronized over time because their state-passing protoco is designed to be resiient enough to message faiure. n other cases, the distributed state mode or the passive state mode Wi be needed in order to truy synchronize them. f the partners exchange state messages, an LACP protoco instance coming up on a standby after the active is aready running Wi synchronize to the same state as the active by viewing the state messages of the partner. n essence, the active contro bade sends its current state to the standby instance via the LACP partner. RSTP exchanges periodic messages in a simiar manner. GMP is something of an issue and requires impementation of the Distributed State Mode approach to get in synchronization. The state is reativey easy to capture since there are very few state machines in the GMP snooping protoco reative to LACP/ RSTP. [0118] The eighth identi?ed disadvantage for the Active Protected Mode Was that it is impossibe to verify that the states are synchronized uness a traf?c to the contro bades are stopped. HoWever, the vaidation of the sequence and content of messages being transmitted to the ine bades is an exceent heuristic of state synchronization. [0119] The ninth identi?ed disadvantage for the Active Protected Mode Was that there is no mechanism to verify that the ine bade states are in synchronization With the contro bades and there is no mechanism to cean up entries. HoWever, synchronization can be vaidated by comparing messages. [0120] The tenth identi?ed disadvantage for the Active Protected Mode Was that memory eaks Wi typicay be re?ected on both contro bades since they are running in parae, and this means that the approach does not protect against software faiures. Memory eaks shoud be detected in advance and/or monitored dynamicay by the heath monitor. This presents a vaid concern that an active-pro tected approach provides minima protection against soft Ware defects. The primary design goa in a redundancy scheme has been primariy to design against hardware faiures. [0121] The Modi?ed Active-Protected Mode can be fur ther modi?ed to incude a cosed oop. This modi?cation requires that there is a connection from ine bades to both contro bades. Since connection oss is a potentia faiure mode, it cannot be guaranteed. [0122] Contro bade synchronization is required for sev era reasons When impementing the above-described mod es via the network switch assemby 10 of FG. 1. [0123] 4. SynchroniZation of Contro Bades [0124] SynchroniZation of contro bades is required for the foowing reasons: [0125] 1. n a singe bade system, if the contro bade faied and rebooted, the ine bades are sti running. t is necessary for the contro bade to recreate its state from the ine bades. [0126] 2. Active Contro Bade Faiure: The main reason is a faiure of the active contro bade. This faiure can be detected by the standby bade by attaching to the main processes running on the active contro bade. When the active contro bade fais, it may or may not ose connec tivity With the ine bades. f the standby takes over, the redundancy manager sends a signa to a the ine bades to queue the signas to the contro bade and make the standby the active contro bade. A reguar traffic is hated Whie the standby bade synchronizes. [0127] 3. Contro Bade SoftWare upgrade. During a soft Ware upgrade, the standby contro bade gets the newer version of software and reboots. At this time it is competey out of synchronization With the active contro bade. t is possibe to synchronize the managers from the ine bades. HoWever, it may take onger or require additiona effort to synchronize the protocos. [0128] n muti-baded redundant systems With a standby contro bade, it is necessary to use the synchronization mechanism to bring the contro bades into synchronization With one another so that they can run in protected mode. [0129] n a singe bade system, if the contro bade reboots, the ine bades continue to run. Signas are queued to the contro in anticipation of the connection being re estabished. f the queue becomes fu, then the signas are dropped on a FFO basis. [0130] When the contro bade comes up it Wi resynchro nize itsef With the ine bades; however, protocos such as RSTP and LACP Wi be starting from scratch. HoWever, ine bades are sti switching packets based on their previ ous RSTP/LACP port con?guration. [0131] At this point these managers shoud have a mecha nism to synchronize themseves. [0132] FG. 8 iustrates by Way of exampe one method for rendering contro entity redundancy in a network switch ing device. As shown in FG. 8, a ogic?ow diagram iustrates the steps of impementing contro entity redun dancy. [0133] n Step S1, a network switching device is provided incuding a?rst contro entity in an active state, a second contro entity in a standby state, and at east one ine bade communicating With the?rst and second contro entities.

15 The ine bade has a puraity of data ports interconnected by Way of switching fabric. After performing Step S1, the process proceeds to Step S2. [0134] n Step S2, the system detects an operating state of the active contro entity. After performing Step S2, the process proceeds to Step S3. [0135] n Step S3, the system generates at east one parameter indicative of the detected operating state of the active contro entity. n one case, a singe parameter is generated. n other cases, mutipe parameters are generated. After performing Step S3, the process proceeds to Step S4. [0136] n Step S4, the process transfers the at east one parameter from the active contro entity to the standby contro entity. After performing Step S4, the process pro ceeds to Step S5. [0137] n Step S5, the process synchronizes the state of the active contro entity With the state of the standby contro entity using the at east one parameter. n one case, a singe parameter is used. n other cases, mutipe parameters are used. After performing Step S5, the process proceeds to Step S6. [0138] n Step S6, the process detects faiure of an active contro entity. n one case, faiure is determined by detecting an error. n other cases, faiure is detected When the active contro entity no onger functions propery. After performing Step S6, the process proceeds to Step S7. [0139] n Step S7, the process converts the standby contro entity into the status of a new active contro entity. After performing Step S7, the conversion process is compete and the overa process returns to Step S1 in order to further impement contro entity redundancy. [0140] n compiance With the statute, the invention has been described in anguage more or ess speci?c as to structura and methodica features. t is to be understood, however, that the invention is not imited to the speci?c features shown and described, since the means herein dis cosed comprise preferred forms of putting the invention into effect. The invention is, therefore, caimed in any of its forms or modi?cations Within the proper scope of the appended caims appropriatey interpreted in accordance With the doctrine of equivaents. The invention caims: 1. A network switch assemby, comprising: a?rst contro entity seectivey con?gurabe between an active state and a standby state; a second contro entity seectivey con?gurabe between a standby state and an active state; and at east one ine bade communicating With at east one of the?rst contro entity and the second contro entity and having at east one port con?gurabe to enabe switch ing of information; Wherein one of the contro entities is con?gured as an active contro entity, another of the contro entities is con?gured as a standby contro entity, and the active contro entity is con?gured to transfer state information for the active contro entity that is forwarded to the standby contro entity. 2. The network switch assemby of caim 1 Wherein the active contro entity is con?gured to transfer state informa tion for the active contro entity directy to the standby contro entity. 3. The network switch assemby of caim 1 Wherein the active contro entity is con?gured to transfer state informa tion for the active contro entity via one of the at east one ine bade to the standby contro entity. 4. The network switch assemby of caim 1 Wherein the?rst contro entity and the second contro entity each com prises a contro bade. 5. The network switch assemby of caim 1 Wherein the ine bade comprises a puraity of Ethernet ports, and the network switch assemby comprises an Ethernet switch assemby. 6. The network switch assemby of caim 1 Wherein the active contro entity comprises a database con?gured to store a state of the active contro entity in database format. 7. The network switch assemby of caim 4 Wherein a system state comprising the state of the active contro entity is transferred to the standby contro entity. 8. The network switch assemby of caim 4 Wherein at east one message is con?gured to record and transfer the state of the active contro entity. 9. The network switch assemby of caim 1 Wherein the?rst contro entity comprises processing circuitry, the second contro entity comprises processing circuitry, and the pro cessing circuitry from the active contro entity communi cates With the processing circuitry from the standby contro entity and is con?gured to transfer a state of the active contro entity to the standby contro entity. 10. The network switch assemby of caim 9 Wherein each of the processing circuitry is provided by a processor, and Wherein both processors are con?gured With substantiay identica hardware con?gurations and run substantiay iden tica versions of software such that identica inputs to both processors Wi produce identica states in both processors. 11. The network switch assemby of caim 9 Wherein the processing circuitry from the?rst contro entity is con?g ured to synchronize the states of the?rst contro entity and the second contro entity. 12. The network switch assemby of caim 11 Wherein the?rst contro entity and the second contro entity each com prise a redundancy manager and the processing circuitry is con?gured to synchronize state information between the respective contro entities. 13. The network switch assemby of caim 12 Wherein the processing circuitry is further con?gured to synchronize protoco states between the respective contro entities. 14. The network switch assemby of caim 11 Wherein, in response to bootup of a switch assemby, the processing circuitry is con?gured to synchronize state information between the?rst contro entity and the second contro entity. 15. The network switch assemby of caim 11 Wherein, in response to the switch assemby running under direction of the one contro entity, upon insertion of the another contro entity, the another contro entity is con?gured to synchronize With the one contro entity. 16. The network switch assemby of caim 11 Wherein, in response to occurrence of a communication faiure between the one contro entity and the another contro entity, the processing circuitry is con?gured to detect a oss of com munication between the respective contro entities.

16 17. The network switch assemby of caim 11 wherein the processing circuitry is con?gured to detect a oss of corn rnunication between the respective redundancy managers, and the switch assemby con?gures the another contro entity as the active contro entity and reboots the another contro entity. 18. The network switch assemby of caim 17 wherein, in response to the switch assernby con?guring the another contro entity as the active contro entity, the another contro entity sends a de-queue signa to the ine bade. 19. The network switch assemby of caim 18 wherein, in response to the ine bade receiving the de-queue signa, the ine bade is con?gured to resend a signas that are not acknowedged to the another contro entity, and de-queue a the queued signas. 20. A network switching device, comprising: a pair of contro entities each having processing circuitry, each contro entity seectivey con?gurabe between an active state and a standby state in an aternating manner such that one contro entity is con?gured in an active state whie another contro entity is con?gured in a standby state; and at east one ine bade communicat ing with the?rst contro entity and the second contro entity and having a switching agent and a redundancy agent; wherein the processing circuitry from the?rst contro entity communicates with processing circuitry from the second contro entity, one of the contro entities is con?gured as an active contro entity and another of the contro entities is con?gured as a standby contro entity, and one of the processing circuitry is con?gured to transfer a state of the active contro entity to the standby contro entity. 21. The network switching device of caim 20 wherein the?rst contro entity cornrnunicates via the ine bade with processing circuitry from the second contro entity. 22. The network switching device of caim 20 wherein each contro entity comprises a switching manager and a redundancy manager. 23. The network switching device of caim 20 further comprising switching fabric, and wherein the ine bade comprises a puraity of data ports interconnected with the switching fabric to enabe data traf?c switching between the data ports. 24. The network switching device of caim 20 wherein one of the at east one ine bade is con?gured to generate and send a message to an active contro entity. 25. The network switching device of caim 24 wherein, in response to receiving the message at the active contro entity, the active contro entity is con?gured to copy the message and forward the copy of the message to the standby contro entity. 26. The network switching device of caim 24 wherein, in response to receiving the message at the standby contro entity, the standby contro entity is con?gured to generate and send an acknowedgment message to the active contro entity. 27. The network switching device of caim 24 wherein each of the contro entities comprises a switching manager and a redundancy manager, and wherein the active contro entity is con?gured to forward the message to the switching manager of the standby contro entity in response to receiv ing the message. 28. The network switching device of caim 26 wherein each of the contro entities comprises a switching manager and a redundancy manager, and wherein, in response to the active contro entity receiving the acknowedgment mes sage, the active contro entity is con?gured to forward the acknowedgment message to the ine bade that originated the message. 29. The network switching device of caim 27 wherein the redundancy manager of the active contro entity is con?g ured to forward the processed message to the switching manager of the active contro entity once the acknowedg rnent has been received by the standby contro entity. 30. The network switching device of caim 26 wherein each ine bade comprises a redundancy agent, at east one switching agent, and a transrnit queue, and wherein the redundancy agent, in response to receiving the acknowedg rnent message, is con?gured to remove the acknowedgment message from the transmit queue of each ine bade, so as to enabe sending of another message to the active contro entity. 31. The network switching device of caim 26 wherein the ine bade is con?gured to send a message to the active contro bade in response to the ine bade receiving acknowedgment of receipt of a previous message sent by the ine bade to the active contro bade. 32. A method for rendering contro entity redundancy in a network switching device, the method comprising: providing a network switching device incuding a?rst contro entity in an active state, a second contro entity in a standby state, and at east one ine bade commu nicating with the?rst and second contro entities and having a puraity of data ports interconnected via switching fabric; detecting an operating state of the active contro entity; generating at east one parameter indicative of the detected operating state; and transferring the at east one parameter from the active contro entity to the standby contro entity. 33. The method of caim 32 further comprising generating an operating signa from the at east one ine bade and transmitting the operating signa to an active one of the?rst contro entity and the second contro entity. 34. The method of caim 33 wherein each ine bade comprises at east one switching agent and a redundancy agent, and further comprising providing the operating signa via the switching agent to the redundancy agent, copying the operating signa, and forwarding the operating signa and the copy of the operating signa via the redundancy agent to the active contro entity and the standby contro entity, respec tivey. 35. The method of caim 32 wherein each contro entity comprises at east one switching manager and a redundancy manager, and further comprising synchronizing the state of the active contro entity with the state of the standby contro entity. 36. The method of caim 35 further comprising, foowing synchronizing the state of the active contro entity with the state of the standby contro entity, generating an input message from the ine bade for receipt at the active contro entity. 37. The method of caim 35 wherein synchronizing the state cornprises synchronizing data tabes within managers of the active contro entity and the standby contro entity.

17 38. The method of caim 35 wherein synchronizing the state comprises synchronizing protoco states with managers of the active contro entity and the standby contro entity. 39. The method of caim 32 wherein transferring the at east one parameter comprises periodicay sending an updated state from the active contro entity to the standby contro entity. 40. The method of caim 39 wherein each of the at east one ine bade comprises an agent communicating with the active contro entity, and further comprising periodicay sending an update state from the active contro entity to the standby contro entity. 41. The method of caim 39 further comprising dupicat ing signa appication program interface cas to a database manager of the active contro entity, and wherein transfer ring comprises sending the dupicated signa appication program interface cas to a database manager of the standby contro entity. 42. The method of caim 32 wherein transferring the at east one parameter comprises, from a ine bade, receiving an operating signa from the active contro entity, dupicat ing the operating signa, and transferring the operating signa to the active contro entity and the standby contro entity. 43. The method of caim 32 wherein transferring com prises generating a message indicative of operating state of the active contro entity, repicating the message, and for warding the message to the active contro entity and the repicated message to the standby contro entity. 44. The method of caim 32 further comprising storing state on each of the ine bades, sending a signa to the active contro entity indicative of the state, and wherein transfer ring comprises sending the signa from the active contro entity to the standby contro entity. 45. The method of caim 44 wherein, in response to faiure of the active contro entity, further comprising queuing any incoming signas via an agent on each of the ine bades. 46. The method of caim 45 wherein, further in response to faiure of the active contro entity, further comprising converting the standby contro entity into a new active contro entity. 47. The method of caim 46 wherein, after converting, sending a synchronization request from the new active contro entity to each of the ine bades. 48. The method of caim 47 further comprising receiving the synchronization request at one of the ine bades and sending state data from the one ine bade to the new active contro entity. 49. The method of caim 32 further comprising, from a ine bade, generating a message indicative of state of the ine bade and forwarding the message to one of the contro entities that appears to be in an active state. 50. The method of caim 49 further comprising receiving the message at the one contro entity and forwarding the message to another of the contro entity that appears to be on standby. 51. The method of caim 50 further comprising generating an acknowedgment message at the another contro entity and forwarding the acknowedgment message to the one contro entity. 52. The method of caim 51 further comprising receiving the acknowedgment message at the one contro entity and forwarding the acknowedgment message to the ine bade. 53. The method of caim 52 further comprising receiving the acknowedgment message at the ine bade and, in response to receiving the acknowedgment message, remov ing the message from a transmit queue of the ine bade. 54. The method of caim 52 further comprising synchro nizing state of the active contro entity with state of the standby contro entity using one or more of the at east one parameter. 55. The method of caim 54 further comprising detecting faiure of the active contro entity. 56. The method of caim 55 further comprising converting the standby contro entity into a new active contro entity. 57. A network switching device, comprising:?rst contro means for con?guring the switching device and seectivey con?gurabe between an active state and a standby state; second contro means for con?guring the switching device and seectivey con?gurabe between a standby state and an active state; and ine bade means for enabing switching of information between ports and communicating with at east one of the?rst contro entity and the second contro entity; wherein one of the?rst contro means and the second contro means is con?gured as an active contro entity, another of the?rst contro means and the second contro means is con?gured as a standby contro entity, and the active contro entity is con?gured to transfer state information for the active contro entity that is forwarded to the standby contro entity. 58. The network switching device of caim 57 further comprising database means con?gured to store a state of the active contro entity in a database format. 59. The network switching device of caim 57 wherein the?rst contro means and the second contro means each further comprise switching means for managing switching between ports of at east one ine bade means. 60. The network switching device of caim 5 9 wherein the?rst contro means and the second contro means each further comprise redundancy means for managing redun dancy of state for ine bade means recorded in the?rst contro means and the second contro means, respectivey. 61. The network switching device of caim 60 further comprising acknowedgment means for acknowedging the transfer of state information to the standby contro entity. 62. The network switching device of caim 57 wherein the?rst and second contro means each comprise a contro bade, and the ine bade means comprises at east one ine bade.