High Speed Shared Memory Networks in Hardware in the Loop Applications

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1 High Speed Shared Memry Netwrks in Hardware in the Lp Applicatins Try Trshynski Avinics Interface Technlgies (A Divisin f Teradyne) Omaha, NE U.S.A. Abstract - As aircraft avinics systems becme mre and mre integrated and cmplex, the verall csts and duratin f system verificatin and validatin effrts cntinue t increase and cntribute t the rising csts f new system design. In rder t cntrl csts, reduce schedules, and imprve verall quality, Distributed Hardware-inthe-Lp (HIL) simulatins are increasingly being used t verify integrated mdular avinics systems. As these systems becme increasingly cmplex, the distributed system must interface with an ever increasing number f aircraft interfaces, sensrs, and actuatrs which ften drives the requirement fr a distributed, real-time prcessing architecture fr the HIL system. This paper prvides a brief technical verview f distributed HIL test systems and als explres the use f a high speed Shared Memry Netwrk fr data sharing and time synchrnizatin between real time prcessrs in a distributed HIL test system. INTRODUCTION Avinics applicatins have becme a netwrk f integrated mdular systems with increasingly mre imprtance n the netwrk used t mve data between each subsystem. Generic maintenance cmmunicatins, highbandwidth vide data, and event-driven real-time data must be integrated int the avinics cmmunicatins netwrk. Initially, mst avinics systems relied n specialty hardware busses and prprietary interfaces t integrate mdular systems. Standard bus architectures like MIL-STD-1553 in military applicatins and ARINC-429 in cmmercial applicatins were the nrm. Hwever, as the systems have becme mre distributed, these busses were simply nt fast enugh r scalable enugh. The Ethernet cmmercial standard (IEEE 802.3) slwly began t be used as the backbne fr cmmunicatins in avinics systems. Ethernet is the defact-standard that has been in use fr distributed cmmercial applicatins fr decades. It is lw cst, and a prven technlgy fr distributed systems applicatins. It is a natural prgressin fr Ethernet t becme the backbne in distributed, integrated mdular avinics systems. Althugh Ethernet ffers many advantages, there are specific avinics applicatins that Ethernet des nt apply itself well t. These applicatins still require netwrked distributin f data but require ther attributes that Ethernet is nt very gd at. These attributes include: High-vlume Data Mvement Deterministic frame transmissin and receptin Redundancy Real-time Event-driven data transfers Fr these types f netwrk applicatins, specialty subnetwrks are available t allw cmmunicatin between the subnetwrk and the main Ethernet backbne. There are quite a few standardized subnetwrks that are well defined and in-use tday. Fr example, the ARINC-664 Netwrk Specificatin defines a netwrk t accmmdate deterministic, dual redundant switched netwrk. ARINC-664 includes redundancy and deterministic behavir that is required fr distributed Avinics netwrk applicatins. Frame Prtcl: Frame layut, flw cntrl Transmissin Prtcl: Encding, wrd transmissin, errr Physical Layer: Cabling, cnnectrs Figure 1 SMN Layers The ARINC-664 standard is very similar t the standard IEEE802.3 Ethernet except that a unique identifier is cntained in the MAC layer called a Virtual Link. The Virtual Link is used

2 by the netwrk switch fr the physical cnnectins, and data ruting needed t pass data between devices. The use f custm ARINC- 664 switches ensures that frames are ruted in a deterministic manner, and dual-redundant endsystems ensure reliability f delivery. ARINC- 664 has been adpted by Being n its 787 cmmercial aircraft prgram and Airbus n its A380, A350 cmmercial aircraft prgrams. ARINC-664 and ther similar Ethernet derivative standards, like AS6802, are subnetwrks with specific real-time attributes, but they lack the capability f real-time event driven transfers. In hardware in the lp applicatins, event driven transfers are key. Fr deterministic, event driven netwrks, the Shared Memry Netwrk (SMN) is the apprpriate chice. Shared Memry Netwrk Overview There are three reasns why the Shared Memry Netwrk (SMN) is a great fit as a subnetwrk fr tightly cupled event driven avinics applicatins: Simple t implement Fast and scalable Lw latency with n prtcl verhead SMN is a simple netwrk where data written t memry lcatins n their lcal nde appears in the RAM n all f the ther ndes, and that writes n the ther ndes will als appear in their RAM attached systems. All data assciated with any lcal event is shared quickly with ther ndes n the netwrk. Interrupts assciated with unpredictable events can be sent t specific ndes n the netwrk, r bradcast. The implementatin is very simple, All data is sent at real-time rates clse t the 2.125Gbps line speed with virtually n verhead. Because f the small verhead, there is minimal latency assciated with data transfer ver the netwrk. SMN s limited prtcl can be defined as three (3) functinal layers. These layers are illustrated in Figure 1. Simple t Implement The Shared Memry Netwrk is based n reflective memry technlgy. This is a methd where multiple systems in a netwrk share data. The netwrk shared data perates like a dual prted memry. Each Shared Memry Netwrk nde is 256 Mbytes. The netwrk peratin is very simple, when an end-system writes data t a memry lcatin n its SMN nde, this data is replicated (r reflected) n all f the ther ndes n the netwrk at the very same memry lcatin. The SMN is an ptical ring tplgy where every End-System is a data surce, and a Receiver. There is n ruting fabric, all data is bradcast immediately when written t a nde. The physical interface fr a SMN prt is a fibre ptic cnnectin. Each fibre ptic prt is simplex, unidirectinal, serial cnnectins. One line fr transmit, anther fr receive. Fibre ptic cables are lightweight, and easy t maintain. There are n large multi-pin cable bundles and cnnectrs. Either single mde r multi-mde ptical cabling can be used. The chice f media type is dependent upn distance, pwer requirements, and weight. The different physical media ptins, with n degradatin f perfrmance, is a real benefit t the Avinics design engineer. Fast and Scalable Shared Memry Netwrk is extremely fast. Currently, Gbps netwrk speeds are all in use tday. All data transfers ccur at line speeds ver the netwrk. The radmap exists fr increasing speeds t 4, 8 r 16 Gbps in future implementatins. High-bandwidth applicatins will scale upward t access the full line bandwidth withut changing the applicatin. Adding additinal End-Systems int an existing netwrk is as easy as just adding ndes t the SMN netwrk ring tplgy. There is n netwrk address re-cnfiguratins, ruting table re-cnfiguratins, r netwrk switching changes that are required. Avinics applicatins can simply add ndes and re-define the applicatin fr sharing the 256 Mbytes memry. Lw Latency with n prtcl verhead The Shared Memry Netwrk implements a prtcl ptimized fr lw latency transmissin f data. All data transmissins are bradcast at netwrk line rates (2.125 Gbps). Each nde uses the same small defined prtcl (hw t mve the data n/ff the netwrk). Hwever, the user applicatin never has t accunt fr prtcl r message delivery. Each nde applicatin simply reads/writes t the shared memry. This enables the netwrked system t perate as a tightly cupled applicatin.

3 The SMN is analgus t a multi-threaded applicatin that shares a cmmn system memry. Each thread perates autnmusly, while the applicatins decide n the partitining and use f the shared memry. In additin, similar t multi-threaded applicatins, the SMN supprts the use f interrupts. Therefre, SMN ndes can generate interrupts fr ther ndes n the netwrk, and pass critical data alng with the interrupt. This is critical fr event driven hardware-in-the-lp and critical real-time applicatins where an event must be handled immediately by a nde in the netwrk. SMN Operatin The Shared Memry Netwrk cnsists f ndes cnnected tgether in a ring tplgy. Each netwrk nde interface uses a Transmit queue fr sending nde data, and a Re-transmit queue fr re-sending data received ver the netwrk. Any nde can write t the lcal Shared Memry RAM, these writes are packetized int small frames, and placed in the transmit queue that inserts the frames int the netwrk traffic during idle times. The queue cnsists f ne (1) t sixteen (16) 32-bit wrds that can be transmitted at a time. In additin t the data, there is a tw (2) wrd header with infrmatin abut the fllwing data (like nde transmit ID, memry index f the data, and number f data wrds). There is a checksum wrd that fllws datawrds being sent. Once placed in the transmit queue, this data is sent ver the ring t the next nde. Each nde has a re-transmit queue that receives all incming data frm the netwrk. The Re-transmit queue determines if the message received is frm itself. If it is the riginatr f the message, then the message is cleared frm the queue. If the message is frm anther nde, then the Shared Memry infrmatin is depsited lcally, and pending n ther messages in the Transmit queue, it is retransmitted immediately n the netwrk. See Figure 2. Figure 2 SMN Nde As stated previusly, the Shared Memry Netwrk prtcl is simple. SMN, like any netwrk architecture, transmits blcks f user infrmatin called packets. Befre sending the actual data ver the physical link, additinal specific cntrl infrmatin is added t the packet. The cmbinatin f the cntrl infrmatin and the data is called a frame. Fr SMN a frame has tw 32-bit wrds f cntrl infrmatin (header) and anywhere frm 1 t bit wrds f paylad (pure data cntaining the user infrmatin). Likewise, every frame is fllwed by an End f Frame delimiter (EOF) which is a 32-bit wrd signaling the end f the frame and a checksum fr packet integrity checking. If the user data required t send is t large t send in ne frame, then multiple frames must be gruped tgether and this frms a sequence. Besides frames f data, SMN als identifies an idle primitive sequence data t be sent ver the link. This type f data is SMN s mechanism t perfrm cntrl and signaling ver the simplex transmissin link. Idle ReTransmit Queue Nde Transmit Queue Wrd 0 Wrd 1 Data EOF Memry Index Interrupts Transmit Nde ID Rgue Message 32-bit datawrds (1-16) Figure 3 SMN frame Frmat Preceding any frame f data, there must be a minimum f 1 IDLE fill wrds. Figure 3 shws the Fibre Channel frame frmat. Checksum & EOF SMN Simulatin Deterministic Data transfers f small amunts f data (4 t 64 bytes) are critical fr simulatin and hardware in the lp avinics systems applicatins. A Hardware in the Lp

4 applicatin must get data t anther systems reliably and n-time. Prir t implementatin, it is imprtant t cmpletely understand the behavir f each individual cmpnent and the whle system during nrmal peratins, as well as behavirs and reactins t system faults. Understanding the mvement f data ver the netwrk as well as understanding the amunt data that is being passed is critical. Setting up the simulatin will ccur in tw phases: Setting up and Testing individual End Systems Testing End Systems in the Netwrk Individual End System Testing Avinics Integrated Mdular Systems are delivered t the airframe manufacturer frm many suppliers. Each Mdular System specializes in a particular functin fr the aircraft (i.e. Navigatin, Cllisin Avidance Radar, Health Maintenance). Individual testing is required fr the unique System as well as simulating the ther End-Systems. Therefre, an SMN must be able t simulate missing data surces in rder t stimulate the Unit Under Test. Testing assciated with individual Mdular End Systems include: Des the Surce data End System prts transmit crrect at apprpriate sync intervals? Hw many transmit errrs are prduced ver a lng time perid? Des the Mdular End System receive and prcess bjects crrectly? Hw des the Mdular End System react t receiving incrrect Objects, frames with prtcl errrs, CRC errrs, r frames with bad data in them? Netwrk System Tests Individual End Systems are eventually integrated int the Mdular avinics netwrk. Effective testing is required during integratin t insure that each End System perates efficiently. This type f testing requires that test equipment is placed in-line between the data surce, and the recipient. Netwrk frame flw testing reveals flaws in the system design and implementatin. Testing assciated with the Integrated netwrk include: Mnitring each End System fr frame errrs assciated with frame mvement ver the netwrk. Checking the deterministic flw f cntainers frm the End System surce. Checking the redundancy f the netwrk (if implemented). SMN Simulatin Example A gd example f a Hardware in the Lp applicatin that requires an SMN is a vehicle self-preservatin system. The typical selfpreservatin system requires three functins Threat detectin Analysis f ptins (cmputing) Avidance and/r Fire Cntrl System Threat Detectin System Fire Cntr l System Figure 4 Self Preservatin System In this example, the Threat detectin and Avidance/Fire Cntrl functins are assciated with hardware sensrs that will either cllect data, r cntrl devices used fr avidance/fire cntrl. A cmputatinal element perfrms the calculatins assciated with analyzing the threats and determining the best curse f actin. This simple mdular architecture splits easily int the three functins required. A self-preservatin system f an armred vehicle best demnstrates the criticality f a deterministic netwrk. The self-preservatin system includes a system fr mnitring sensrs that detect threats, a cmputatinal system, and a weapns system that will eliminate the threat rather than avid it. Each f these systems are nt c-lcated within the vehicle, s a netwrk interface instead f a bus architecture, is best suited t cnnect these mdular functins. I will shw hw standard IEEE Gigabit Ethernet and Gigabit ARINC-664 can be used versus SMN as the netwrk that best fits this requirement. Ethernet and ARINC-664 Cmputatinal System In ur example, the armred vehicle prceeds at a variable speed alng a path.

5 Initially, nly lw vlume maintenance cmmunicatins ccurs between the three mdular systems. When the Threat detectin system btains infrmatin frm its sensrs that a threat has been detected. Fr example, a handheld missile system perating within firing range f the vehicle is detected. Only a cuple f secnds are available t acquire the threat, analyze ptins and fire the weapn t eliminate the target (r pssibly cmmunicate with anther system t avid the incming threat). The Threat detectin system must interrupt the rutine maintenance netwrk traffic and immediately reprt its threat infrmatin t the Cmputatinal system. The amunt f data reprted by the Threat detectin system wuld be small, typically less than 64 bytes indicating psitin and range infrmatin. Additinal display infrmatin might fllw, which is mre data. In a standard Ethernet netwrk, the Threat detectin system wuld send this infrmatin ut as an Ethernet packet. If there is nt existing traffic n the netwrk that might cause a cllisin (which wuld delay the data), the packet culd be sent withut any delay, but any traffic n the netwrk wuld cause an unknwn delay. In the ARINC-664 netwrk (deterministic, time divisin multiplexed with defined latency and jitter), the Threat detectin system wuld send the infrmatin ut as an Ethernet packet. Since an ARINC-664 netwrk assigns each Virtual Link a Bandwidth Allcatin Gap (BAG) time which guarantees n cllisins n the netwrk with ther traffic, the packet culd be sent with a maximum latency f 1 millisecnd after receipt f the threat data. In additin, bth Ethernet and ARINC-664 must transfer a minimum f 64 bytes in a frame. In ur applicatin nly a small amunt f data, 16 bytes, is required (ntably lcatin infrmatin cnsisting f latitude and lngitude). Despite the small data size, a 64-byte frame must be sent and prcessed by the receiving nde. After the cmputatinal system perfrms its analysis, its infrmatin must be sent ver the netwrk t the fire cntrl system. The Fire Cntrl system will use the infrmatin t direct the anti-missile fire at the ncming prjectile. The transfer f infrmatin between the Cmputatinal system and the Fire Cntrl system must be cmpleted as quickly as pssible. Here again, using standard Ethernet fr this netwrk transfer, delays can ccur due t cllisins n the netwrk, and pssible prtcl prcessing assciated with the send and receipt f Ethernet packets. Likewise, if we substitute an ARINC-664 netwrk t take advantage f its deterministic behavir, it wuld perfrm better than standard Ethernet, but there are still delays assciated with BAG latencies. Shared Memry Netwrk By cntrast, a Shared Memry netwrk is a better architecture fr ur Hardware in the Lp applicatin. The reasns that the SMN will perfrm better is its ability t: Generate an immediate interrupt n anther system Transmit data at full line speed (2.125 Gbps) Eliminate prtcl prcessing, s interrupted applicatins can begin prcessing data in accessible memry. In the example applicatin, the Threat detectin system can generate an interrupt n the SMN t the Cmputatinal system alng with sending the threat data. There is n risk f cllisin n the netwrk, since all nde utput data takes pririty ver anything being received. This is a key advantage and why the SMN meets event-driven applicatin requirements. Upn receipt f the interrupt, the Cmputatinal system can act immediately upn the Threat data stred in its memry. Then after perfrming the cmputatins, it can immediately interrupt the fire cntrl system with data required fr eliminatin f the incming threat. CONCLUSION Shared Memry Netwrk (SMN) is a deterministic, event-driven netwrk technlgy that is designed fr real-time simulatin applicatins. The SMN is based n reflective memry ring netwrk architecture. The SMN defines a lw latency prtcl that defines the mvement and mapping f data in shared memry amng netwrk systems. The SMN is ptimized t mve high-bandwidth, lw latency data, reliability and with determinism. These are key requirements fr mst Avinics simulatin systems. Mst simulatin and hardware in the lp applicatins need event driven mvement f data with event driven interrupts. The SMN meets these requirements and it is simple t implement and scalable. In additin, SMN will meet extremely tight timing requirements within the

6 netwrk. The efficiency and availability f the data traversing the SMN netwrk t applicatins is far better than standard Ethernet r Deterministic Ethernet. SMN is an ideal sub netwrk fr hardware in the lp applicatins. References [1] Reflective Memry, Frm Wikipedia, the free encyclpedia [2] Avinics Interface Technlgies, Shared Memry Netwrk Interfaces, [3] Avinics Interface Technlgies, SMN Hardware Manual, 2015 [4] GE Fanuc., Real-Time Netwrking with Reflective Memry, [5] Curtiss Wright, SCRAMNet+ Shared Memry Speed, Determinism, Reliability, and Flexibility fr Distributed Real-Time Systems, IEEE. Persnal use f this material is permitted. Permissin frm IEEE must be btained fr all ther uses, in any current r future media, including reprinting/republishing this material fr advertising r prmtinal purpses, creating new cllective wrks, fr resale r redistributin t servers r lists, r reuse f any cpyrighted cmpnent f this wrk in ther wrks.

CCNA 1 Chapter v5.1 Answers 100%

CCNA 1 Chapter v5.1 Answers 100% CCNA 1 Chapter 6 2016 v5.1 Answers 100% 1. Which characteristic f the netwrk layer in the OSI mdel allws carrying packets fr multiple types f cmmunicatins amng many hsts? the de-encapsulatin f headers