Gigabit Ethernet and Pleora s iport Connectivity Solution

Transcription

1 Gigabit Ethernet and Pleora s iport Connectivity Solution Pleora Technologies Inc.

2 Table of Contents 1. Ethernet Overview The Benefits of Gigabit Ethernet (GigE) for Vision GigE vs. Other Standards Basic Elements of GigE Vision Networks How iport Uses GigE GigE Network Configurations with iport Additional Sources of GigE Information Glossary of Terms Pleora Technologies Inc. 2

3 1. Ethernet Overview The Ethernet transport protocol was developed more than 25 years ago and pioneered by Intel, Digital, and Xerox. Since then, it has evolved to address changing networking requirements and growing demand for more bandwidth. Today, it s the dominant LAN (local-area network) technology, covering 97% of all installed network connections, including those for mission-critical applications. Ethernet is part of the seven-layer protocol stack defined in the OSI Reference Model for networks carrying IP-based services. As shown in Figure 1, Ethernet operates at Layer 2, or the Data Link layer, of the stack. Figure 1: Ethernet operates at Layer 2 of the protocol stack defined in the OSI Reference Model Ethernet transports data in packets to any network-connected device. As shown in Figure 2, a packet is standardized set of bits with a header, payload, and trailer. The header ensures the packet is assembled, prioritized, transmitted, and received in accordance with the OSI model. The payload is the data, and the trailer contains information for error checking Pleora Technologies Inc. 3

4 Header Payload Trailer 64 bits 48 bits 48 bits 16 bits 46 to 1500 bytes 32 bits Preamble Destination Address Source Address Type / Length Data Frame Check Sequence (CRC) Figure 2: All Ethernet packets, including GigE packets, are comprised of payloads, headers, and trailers Ethernet is very flexible, easy to implement and manage, and highly scaleable. On one network, over ordinary Cat-5 copper cable, Ethernet links can operate at data rates of 10 Mb/s, 100 Mb/s, or 1,000 Mb/s. Links at all rates interwork seamlessly, allowing users to allocate bandwidth as needed in a multi-pronged network. Links at 10 Mb/s are known as 10BASE-T connections, links at 100 Mb/s are known as Fast Ethernet (either 100BASE-TX or 100BASE-FX), and links at 1000 Mb/s, or 1 Gb/s, as Gigabit Ethernet (GigE). For next-generation applications, Ethernet industry groups are already developing the 10GigE standard, which operates at 10 Gb/s. 10GigE operates today over fiber. A version of the standard for copper is expected in In addition to supporting higher data rates, Ethernet standards are evolving to meet growing requirements to provision and manage different classes of traffic. Most of today s commercial Ethernet equipment supports sophisticated QoS (Quality of Service) rules, making it suitable for carrying latency-sensitive traffic, such as voice and video Pleora Technologies Inc. 4

5 2. The Benefits of Gigabit Ethernet (GigE) for Vision The 1 Gb/s data rate delivered by GigE supports image transfers at about 125 MB/s, making GigE links suitable for roughly 90% of today s advanced vision applications. GigE links offer superior reach, supporting point-to-point connections of up to 100 meters over Cat-5 cable, and further with LAN switches or fiber. The long reach of GigE allows PCs used for vision system control and image processing to move from operations areas into designated computer centers, paving the way for large numbers of costly, industrial-strength PCs to be replaced by a few centralized, high-powered servers. In general, the benefits of GigE for vision applications can be summarized as follows: Reliable, proven, off-the-shelf technology with large installed base Cost-effective, easy to implement and manage > leverages rich base of commercial applications software Low-latency sustained video transfers up to 125 MB/s: - over distances up to 100 meters without regeneration - beyond 100 meters with low-cost Ethernet switches or fiber Application-independent > supports a range of application-specific requirements Highly scalable - bandwidth scales to multi-gigabit rates by adding Ethernet server adapters and LAN switches - large numbers of cameras and PCs can be supported by one network Full-duplex transfers (bidirectional), allowing cameras or video devices to be controlled like any other IP-connected network device Ability to encapsulate serial control signals (such as RS-232 or system-based General Purpose I/O (GPIO) signaling) for remote transfer and control Dedicated links > multiple IP devices can be connected together without sharing the same bandwidth in a daisy chain Wide range of camera-to-pc networking options: Pleora Technologies Inc. 5

6 - single camera to single PC, multi-camera to single PC, single camera to multi- PC, and multi-camera to multi-pc True networked architecture > supports image data multicasting, or the simultaneous transmission of one image to multiple destinations Reduced system complexity > replaces specialized framegrabber board with standard GigE NIC (network interface card/chip) 3. GigE vs. Other Standards The most common non-ethernet standards for vision applications are Camera Link, Firewire (IEEE 1394b) and USB 2.0 (Universal Serial Bus). Table 1 summarizes the attributes of all four standards. Camera Link, designed for high-performance vision applications, streams data reliably at very high rates up to 7.14 Gb/s over dedicated point-to-point copper links of 10 meters or less. This short reach limits its usefulness in many applications, because PCs are essentially tethered to cameras. Fiber optic extenders stretch the reach to 500 m, but at significant expense. Camera Link is also limited on the networking front, with no flexibility for interconnecting multiple cameras or centralizing control and maintenance. In terms of cost, Camera Link runs over specialized cable and terminates on PCI framegrabbers, both of which enjoy few economies of scale. Despite its limitations, Camera Link delivers unmatched data rates, and is supported by a wide range of high-end camera manufacturers. 1394b is a consumer standard developed for linking digital camcorders to PCs. It offers plug and play usability, and uses a readily available, low-cost PC interface. 1394b is based on a bus topology, where 800 Mb/s is shared by up to 63 devices in a daisy chain network. Devices can be separated by 4.5 meters, to a maximum length of 72 meters over twisted pair copper cable Pleora Technologies Inc. 6

7 1394b sends data over both asynchronous and isochronous channels. Asynchronous links are typically used for latency (delay)-tolerant data, such as control signals, and isochronous channels for latency-sensitive data like video. Of the available bandwidth, 512 Mb/s can be allocated to a single camera over an isochronous channel. With the shared bus, however, only one camera can access this bandwidth at a time, which means high-priority data can be delayed, and reliability compromised. Moreover, 1394b does not include error-checking for isochronous transfers, so data delivery over these links is not guaranteed. Since one PC can remotely control multiple cameras, the scalability and networking flexibility of 1394b is superior to that of Camera Link. However, even at the maximum rate of 512 Mb/s, 1394b data transfers are too slow to support higher-end digital cameras. Many high-speed applications also require real-time PC processing, which is difficult with 1394b s Windows driver, which hogs the PC s CPU during data transfers. Some companies have addressed this limitation by developing their own driver. Another drawback of 1394b is the price of its copper cable. Cat-5 LAN cable, which costs up to 10-times less, can be used instead, but this limits total available bandwidth to 100 Mb/s. Numerous companies support 1394b and their cameras are popular in applications where performance requirements are not overly rigorous, such as microscopy and scientific imaging. USB 2.0, a consumer standard for connecting peripherals to PCs, has much in common with 1394b. It leverages a built-in PC interface, uses a shared bus, and supports asynchronous and isochronous transfers. USB 2.0 delivers up to 480 Mb/s of bandwidth, shared by up to 127 hub-connected devices in a master/slave relationship. Direct PC connections extend up to 5 meters. Hubs extend the reach to 30 meters, with maximum spans of 5 meters between devices Pleora Technologies Inc. 7

8 Like 1394b, USB 2.0 is best suited for less-demanding applications. Only a few vendors have released USB 2.0 cameras, and the standard is having a relatively low impact on the vision system industry. GigE stacks up well against Camera Link, 1394b, and USB 2.0, delivering a unique combination of high bandwidth, networking flexibility, distance, and scalability that makes it the clear winner. GigE is also the only standard that supports wireless connections, and the only one to leverage low-cost Cat-5 copper cabling. GigE uses dedicated links, so bandwidth is not shared between cameras, as it is with 1394b and USB 2.0. GigE also supports many connection options, including one camera to one PC, multiple cameras to one PC, one camera to multiple PCs, and multiple cameras to multiple PCs. In configurations with multiple cameras or PCs, interconnections are through full-duplex, inexpensive Ethernet switches. PCs links are through RJ-45 plugs, which are either already on the PC or added via low-cost network interface cards. Moreover, GigE goes the distance, supporting individual links of 100 meters over Cat-5 copper. With switches, the reach is virtually unlimited. This means PCs can migrate out of operations areas, and control and maintenance functions can be centralized in one room. Ethernet s networking flexibility also allows image data to be multicast, or simultaneously distributed, to multiple PCs, allowing, for example, one PC to display the image, one or more to process it, and another to archive it Pleora Technologies Inc. 8

9 Criteria Ethernet 1394B USB Camera Link Type of Standard Commercial Consumer Consumer Commercial Connection Type Point-to-point or LAN Peer-to-peer Master-slave Point-to-point Bandwidth < 1000 Mb/s < 800 Mb/s (but only 512 Mb/s for image data) < 12Mb/s, USB1.1 < 480 Mb/s, USB2 Topology Link Bus Bus Link Cabling RJ-45, Cat-5 (4 x twisted pair) 4/6 pin STP 4 pin STP External Camera Interface adapter or built Built-in Built-in Built-in in - Max with switches - Max with fiber optics Base: 2,380 Mb/s Med: 4,760 Mb/s Full: 7,140 Mb/s MDR-26-pin for Camera Link PC Interface GigE NIC PCI card PCI card PCI Framegrabber Data Transfer Type Dedicated Asynchronous / Asynchronous / Isochronous Isochronous Dedicated Streaming Video Continuous Burst Burst Continuous Distance < 100 m < 4.5 m (full < 5 m < 10 m bandwidth) no limit 72 m 30 m no limit 200 m Wireless support Yes No No No Scalability max # of devices Unlimited (cameras) Full Duplex Mode Yes Yes Yes Yes Network Control Yes Yes No No I/O Control RS-232 or GPIO Yes Yes Yes Virtual Link Support Yes Yes No No Area Scan Support Yes Yes Yes Yes Line Scan Support Yes Limited No Yes Multi-Camera Support Windows driver Yes Yes No Native or Proprietary Yes, with multi-framegrabber configuration Native Native Proprietary Table 1: Comparison of Transport Standards for Vision Applications Pleora Technologies Inc. 9

10 4. Basic Elements of GigE Vision Networks Typically, a vision network based on GigE consists of three key elements: data packets, the camera interface, and the physical infrastructure. i) Data Packets Each data packet usually represents a line of data from an area scan or line scan image. Packets are sequentially labeled as they are created. This ensures that the integrity of the original image is preserved when re-constructed at the receiving end of the network, regardless of the order in which packets are received (packet ordering can sometimes change due to packet re-transmits). ii) Camera Interface To interwork with GigE network links, video or imaging cameras must be equipped with an Ethernet interface. Ethernet links are full duplex, which means data flows in both directions. The camera-to-ethernet interface thus allows image data to flow from the camera to the PC, and control data to flow from the PC to the camera. Figure 3 shows a basic, point-to-point bi-directional Ethernet link between a camera and a PC. Figure 3: Point-to-point bidirectional Ethernet link The camera-to-ethernet interface can be executed in two ways. One approach is to use an IP/Ethernet communications software stack running on a microprocessor with an embedded O/S (operating system). For vision applications, this approach is only suitable Pleora Technologies Inc. 10

11 for lower-performance requirements, since at higher data rates the interface consumes high levels power potentially 25 W (Watts) at GigE s full 1-Gb/s rate. The other approach and the one used by Pleora in iport Connectivity Solutions is purpose-built processing hardware. In this method, the packet processing function is hard-coded, eliminating the need for an embedded O/S. This allows data to be packetized with clock cycle accuracy and delivers predictable, low latencies, usually less than 500 microseconds. Purpose-built hardware also consumes much less power. Even at 1 Gb/s, the camera interface in Pleora s solution consumes less than 2.25 W. And, with no O/S programming overhead, purpose-built hardware is also easier to integrate into cameras. iii) Physical Infrastructure In addition to the camera interface, GigE vision networks have four other physical components: Cat-5 copper cable 1, RJ-45 connectors, NICs, and LAN switches. All four of these components are standard Ethernet equipment used in commercial LANs. As such, they are low cost, reliable, and easy to deploy. Two types of Cat-5 copper cable can be used: UTP (unshielded twisted pair), which is suitable for office environments, and FTP (foil-screened twisted pair), shielded for industrial environments. NICs are PC cards. Their main function is to receive and process packetized image data from the camera, and packetize and send control data to the camera. Each NIC has a unique IP address that differentiates it from other network devices. Many PCs offer a GigE interface directly on the motherboard, and thus do not require a separate NIC. GigE is rapidly becoming part of the standard PC configuration. Soon, separate GigE NICs will seldom be needed. 1 GigE packets can also be transmitted over fiber optic cabling, but in this case a different connector than the RJ-45 type is used. Since iport only supports the RJ-45 interface, transfers over fiber require fiber-to- Cat-5 adapters at each end of the link so that termination points (camera, PC) are Cat-5-based Pleora Technologies Inc. 11

12 LAN switches are used in applications where multiple point-to-point links need to be connected together. These switches, which operate at Layer 2 or Layer 3 of the OSI stack, have the following characteristics: they support one input port per video device or link; they handle all bi-directional data traffic between video devices or links and the control PC; they support links operating at different speeds (i.e. 10 Mb/s, 100 Mb/s, 1 Gb/s); they support bandwidth aggregation (i.e. ten 100-Mb/s input links into one 1-Gb/s output link); they extend network reach beyond individual link limits of 100 meters; they maintain system performance and reliability; and they handle real-time address management. The most common Ethernet LAN configuration is the star shown in Figure 4. In this example, three cameras have separate links into one switch, which in turn connects to a control PC. Large-scale networks can consist of multiple switches, multiple PCs, and an unlimited number of cameras. In these networks, control and imaging data can also be configured to flow simultaneously to multiple PCs or cameras. Figure 4: The star is the most common Ethernet LAN configuration Pleora Technologies Inc. 12

13 5. How iport Uses GigE Pleora s iport Connectivity Solutions build on the flexibility and scalability of Ethernet. iport adds a protocol layer on top of GigE so that video, imaging, and control data can be transferred with low, predictable latency between cameras and PCs at up to 1 Gb/s (about 120 MB/s). iport transports the data over low-cost Cat-5 cable. As shown in Figure 5, the protocol delivered by iport handles all networking and applications functions in Layers 2 through 7 of the OSI stack. Layer 1 is the physical connection provided by the Cat-5 cable or fiber. Figure 5: Pleora s iport solution handles all networking and applications tasks associated with Layers 2-7 of the OSI stack As part of its protocol, iport guarantees that data is never lost that every image frame sent by every camera is received intact by destination PCs. To compensate for network disturbances, iport continuously performs automatic error checking and, if necessary, resends packets. iport thus removes the complexities of the entire network connection from the vision application, so that the camera-to-pc connection is always transparent. Pleora s iport Connectivity Solutions have three components: iport IP Engines, which convert video data including Camera Link, LVDS, RS- 422, NTSC, PAL, CCIR, RS-170, and raw digital data streams into IP packets for GigE transport to PCs. In the other direction, the engines convert packetized Pleora Technologies Inc. 13

14 control data to RS-232 or other digital formats for input to cameras. The engines can be incorporated inside cameras, or sit outside as small interface modules. The heart of each iport IP Engine is the iport Protocol Engine, low-power purposebuilt hardware that uses NO embedded O/S, easing in-camera integration. The iport Protocol Engine delivers video payloads at rates of up to 1 Gb/s with low, predictable latency; the iport High-Performance IP Device Driver or iport Universal IP Filter Driver, which run on standard PC NICs. These drivers support demanding applications, such as those with real-time processing requirements, by allowing incoming IP/Ethernet packets to gain direct access to memory, bypassing the Windows or Linux software stack. The iport High-Performance IP Device Driver, for example, streams image data into the PC using only a small fraction of the CPU typically less than 1% leaving the other 99% available for simultaneous image processing tasks. For applications that do not require real-time PC processing, a standard PCI bus device driver can be used; and the iport SDK, which gives customers the building blocks needed to quickly and easily enable third-party or custom video applications. The SDK provides tools for communications, imaging, camera control and display, and software architecture management. It also includes working applications for functions like camera control, image acquisition, and image display. GigE connections to iport IP Engines, PC NICs, and Ethernet switches are all based on simple RJ-45 connectors. This makes the initial deployment of iport GigE vision networks, as well as subsequent network reconfigurations or expansions, straightforward plug and play exercises. iport vision applications can be expanded quickly and easily by adding more Ethernet switches, by adding more PCs to existing switches, or by increasing the PCI bus bandwidth of one PC to handle additional GigE ports. All these expansion options can be implemented without affecting existing camera-to-pc links. The standard PCI bus Pleora Technologies Inc. 14

15 supports one GigE link. The PCI 2.3 bus supports up to 4 GigE links, and the PCI-X bus supports up to 8 GigE links Pleora Technologies Inc. 15

16 6. GigE Network Configurations with iport Pleora s iport Connectivity Solutions support a flexible range of network topologies, including traditional point-to-point camera-to-pc connections, and star configurations, where multiple video devices are connected via an Ethernet switch to one or more PCs. Where multiple links are used, it s important to remember that, unlike Firewire, GigE is NOT a daisy chain bandwidth is not shared between links or devices. a) Single Video Source Single Destination This scenario is the standard point-to-point configuration shown in Figure 6. Like all GigE network links, the Cat-5 connection between the iport IP Engine and the NIC in the PC can extend up to 100 meters. Depending on the data rate required, one of the iport device drivers can be used to bypass the Windows or Linux stack for Direct Memory Access (DMA) into PC memory. Either way, the image data is converted from packets back into ready-to-use images. As with Camera Link-to-framegrabber connections, the GigE link is bidirectional, allowing control signals (RS-232 or GPIO) to be passed back to the camera. Figure 6: iport and GigE in a traditional point-to-point connection Pleora Technologies Inc. 16

17 b) Single Video Source Multiple Destinations This configuration can be used in applications like x-ray imaging or OCR (optical character recognition), where image data from one source needs to be multicast, or simultaneously distributed, to multiple PCs or other destinations. Figure 7 shows an x-ray imaging application using this multicast capability. Since x-rays are used, and emissions are a safety concern, links of about 30 meters are desired, which are easily supported by iport. The GigE link from the camera terminates in a four-port Ethernet switch. The three GigE outputs terminate at three separate PCs. One PC is used to display the image, the second to process it, and the third to archive it. All GigE links are bidirectional; including those between the PCs. Inter-PC control is handled via one of the PCs. Figure 7: iport and GigE in an x-ray distribution network Figure 8 is an example of how iport s multicasting capability could be used to process an OCR application, such as identifying hand-written addresses on mail pieces Pleora Technologies Inc. 17

18 The image of the address is captured by one camera and sent simultaneously to three PCs. The PCs are configured as a processing cell, with each computer optimized to process a different style of handwriting. The application selects the best of the three processing results to direct the mail piece to the appropriate bin. This approach offers an economical, scalable alternative to boosting the power of one PC with DSP (digital signal processing) or FPGA-based add-on cards. The fourth PC can be used as a controller, or to process images of other information sources on mail pieces such as bar codes which may not require as much processing power. Figure 8: The multicasting capabilities of iport and GigE can be used to distribute the processing of an image from one camera across multiple PCs c) Multiple Video Sources Single Destination This configuration can be used in applications like surveillance, where coverage areas are divided into zones, and multiple cameras are installed in each zone. A single PC controls and receives image data streams from all zones, and all links are bi-directional. As shown in Figure 9, each camera is connected via an iport IP Engine into a GigE link that terminates at a GigE switch, with one switch per zone Pleora Technologies Inc. 18

19 The zone switches terminate at a final switch with a single link to a central command PC. The PC activates the zones, as well as the cameras in each zone, in cycles defined by the application requirement and the data rate. For example, images can be sequentially acquired from each camera (cameras share a common sync) in a repetitive cycle until triggered to stop. Local display PCs can also be connected to zones, if desired, as illustrated in Zone D. Figure 9: iport and GigE in a fan-out surveillance network iport IP Engines can intelligently gear down or gear up camera frame rates to accommodate individual applications. For example, if ten 1,000 x 1,000-pixel cameras running at 30 f/s (frames per second) are connected through a GigE switch to one PC, 300 MB/s of bandwidth is needed to transfer all the images to the PC simultaneously. This bandwidth requirement is about three times higher than the 120 MB/s capacity of the GigE link between the switch and the PC Pleora Technologies Inc. 19

20 The iport IP Engines could be set up to reduce the transmission rate to 10 f/s, allowing images to reach the PC at rates the switch-to-pc link can accommodate. The engines could also be set up to increase their transmission rate to 30 f/s if an event occurs, allowing them to transmit the image at high resolution. During this period, the other iport engines on the network could be configured to reduce their rate to 7 f/s, so as not to overwhelm the link, but still provide a steady stream of images from all cameras. d) Multiple Video Sources Multiple Destinations This distributed configuration can be used in applications such as web inspection in a rolling steel mill or newsprint manufacturing facility, where multiple line scan cameras are installed across the width of the web to provide end-to-end vision coverage. Figure 10: iport and GigE in a multi-camera, multi-pc inspection network Each camera is connected to an iport IP Engine, as shown in Figure 10. The cameras are synchronized via the iport GPIO controller to allow continuous data capture linked directly to the variable speed of the web. For the image processing to keep up with the web, the cameras operate at about 60 MB/s (i.e. 60 K lines per second of 1K pixels each) Pleora Technologies Inc. 20

21 The data processing function is shared among multiple PCs synchronized via the network. Each camera can be mapped to one or more front-line processing PCs and one control PC. The control PC performs a final analysis of the results of the front line processing PCs, and controls the complete web process, including I/O control, via RS-232 or GPIO, of the cameras and processing PCs Pleora Technologies Inc. 21

22 7. Additional Sources of GigE Information A more detailed understanding of GigE technology can be obtained from Pleora Technologies ( or from white papers available at the following sites: Glossary of Terms Cat-5 DMA DSP Full Duplex Firewire FPGA FTP f/s Gb/s GigE GPIO IP LAN Mb/s MB/s Multicast NIC O/S OSI Packet PCI Port QoS RS-232 TOE UTP - Category 5 cabling, defined by ANSI/EIA Standard 568 for IP networks - Direct Memory Access - Digital signal processing - Data travels simultaneously in both directions between camera and PC - IEEE 1394 A/B protocol for daisy chain serial connections - field programmable gate array - foil shielded twisted pair, Cat-5 cable type for industrial environments - frames per second - Gigabits per second - Gigabit Ethernet, with 1,000 Mb/s (or 1 Gb/s) max data rate - General Purpose Input/Output - Internet Protocol, the Layer 3 OSI protocol for IP/Ethernet networks - Local Area Network - Megabits per second - Megabytes per second - simultaneous transfer of image data to multiple destinations - Network Interface Card, connects LAN to the PC - software operating system - Open Systems Interconnection, the 7-layer IP/Ethernet network stack - a unit of data exchanged in IP/Ethernet networks - Peripheral Component Interconnect, general-purpose PC data bus - Ethernet connection on the switch and NIC - Quality of Service - Recommended Standard 232 (IEEE computer serial interface) - TCP/IP offload engine - Unshielded twisted pair, Cat-5 cable type for office environments Pleora Technologies Inc. 22