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iPCA Makes Quality Awareness on IP Networks Easy INTERNAL iPCA Makes Quality Awareness on IP Networks Easy — What Advantages Does an Agile Network Bring? (Issue 3) By Swift Liu, President Enterprise Networking Product Line Huawei Enterprise Business Group Agile means quick and nimble. New services such as mobility, cloud computing, social media, Big Data, and the Internet of Things (IoT) bring higher requirements for real-time service transmission, network mobility and scalability, as well as improved user experience. Huawei Agile Network Solution focuses on ways to cope with the challenges brought by these new services and quickly solve problems they create for traditional networks. This article discusses how to monitor the quality of IP networks and facilitates network operation and maintenance (O&M). 1 Challenges to Enterprise Networks Brought by Social Media and Multi-Service Social media is a challenge to network capacity. Different services place different requirements on network quality. For example, the packet loss ratio of voice service should be smaller than 10-2 and that of High Definition (HD) video service should be smaller than 10-6. That is, voice quality degrades if one packet is lost among 100 packets, and video pixelation will appear if one packet is lost among 1 million packets. On traditional enterprise networks, the data traffic of voice and video services is small. With the development of interactive services, real-time traffic increases quickly. Moreover, the services requiring data interaction have high requirements on network quality. Low data traffic of voice and video has little impact on networks, but bursts of traffic will affect networks. Take TV stations for example, where multiple HD channels access multiple studios. If six channels access the same studio, traffic bursts will be generated. A switch’s buffer may fill quickly, which causes congestion that loses packets. Gaming companies provide another example, because traffic bursts of HD video are much larger. The biggest challenge of social media is the impact of multi-service on networks. A network needs to transport 2017-05-04 Huawei Proprietary - Restricted Distribution Page1, Total4 iPCA Makes Quality Awareness on IP Networks Easy INTERNAL services that have different quality requirements and limits on traffic bursts. How can a network transmit all these services and still guarantee service quality? For enterprises, pixilation during video conferences is a big problem; however, the pixilation disappears quickly. How do we locate the fault? Did the problem occur in the video conferencing system or the network? Is there a faulty network link or device? Which card failed? Traditional IP networks cannot locate the fault. Therefore, in most cases, users just endure experience degradation. An agile network should be able to transport all these services and facilitate network operation and maintenance. 2 Innovation 3: IP Quality Awareness IP is a connectionless protocol, and is unaware of network quality. Therefore, fault location is difficult for IP networks and a problem for carriers. However, IP is still widely used. IP was invented by the U.S military during the Cold War, but civilians have made wide use of IP. Basically, IP is reliable because every node on an IP communications path is intelligent. For example, when a serious typhoon assaulted the east coast of the U.S in 2008, all mobile phones and fixed phones were unavailable. The only available communication channel was email. Although IP is a connectionless protocol, many connection-oriented technologies have been introduced so that the Internet Service Provider (ISP) networks can transmit voice as well as data. To monitor IP network quality, people invented many technologies. One method is to continuously send detection packets to test whether a link is normal; that is, a network node continuously sends detection packets to another node. If one packet is lost, an alarm is generated. If three consecutive packets are lost, the system considers that the link is broken, and switches services to a backup link or takes other measures. Huawei has invented a new method — Internet Packet Conservation Algorithm (iPCA) — to implement IP quality awareness. With the traditional method, devices A and B are directly connected, and device C is a tester. Tester C may send 10,000 packets to A and B. Count the packets received by interfaces A1, A2, B1, and B2. If an interface receives 9999 packets, one packet has been lost. The counters on A1, A2, and B1 show that both A1 and A2 have received 10000 packets, but B1 received 9999 packets. Obviously, one packet has been lost on the link between A1 and B1. Why can’t the counters be used to detect packet loss? Because each interface has a large number of counters, we can only view the counters at a specified moment. However, a real service interface, for example, a 10G interface, sends several millions of packets within one second. We cannot obtain the counters of sent and received packets at the same time. Even if the time difference is 1 second, the error may reach several million packets. Therefore, if 2017-05-04 Huawei Proprietary - Restricted Distribution Page2, Total4 iPCA Makes Quality Awareness on IP Networks Easy INTERNAL we cannot see the values of all counters at the same time, we cannot determine whether a packet has been lost. In addition, the transmission/receive time of different devices may not be the same even if the 1588v2 protocol is used. iPCA can address these problems. It uses a reserved bit in IP packets to monitor service quality. The device sets the reserved bit to 0 in an interval, and to 1 in the next interval, and marks, or colors, the packets. Then the device detects the reserved bits in IP packets and calculates the packets. Therefore, the time difference will not affect the calculation result. The simplest Network Time Protocol (NTP) synchronization can meet transmission requirements. iPCA provides the following benefits: 1. Quality monitoring for WAN dedicated lines Most enterprises lease dedicated lines from ISPs to connect their WANs. Actually, a dedicated line is not merely a fiber. It passes many routers and switches on an ISP network. The line may be a L3VPN or L2VPN line. A large number of packets are lost on the dedicated lines. Why are users unaware of the packet loss? As we know, TCP has a retransmission mechanism, and so does the application layer. Therefore, services are not interrupted. However, service quality will still degrade. In this situation, iPCA can be deployed on the egress and ingress of a dedicated line so that all lost packets are recorded. 2. Link quality control on an HD video conference network On a video conference network, the customer is clear about the network structure. After iPCA is deployed, the customer knows where the packets are lost. Therefore, the network administrator can monitor the quality of video conferences, quickly detect faults or potential faults, and take measures to rectify them. 3. Campus network quality control Generally, the switches on a campus network have small buffers. When congestion occurs, packets are lost. The upper-layers (TCP or application layer) have a retransmission mechanism, so the loss of a few packets can be ignored. User experience degrades only occasionally. In this situation, network administrators cannot find problems on the network. Most customers endure this problem because it happens so often. Packet loss occurs frequently, but cannot be located. Huawei iPCA can help network administrators locate the problem on a specific device or link. With iPCA, customers can monitor service quality on campus networks and eliminate potential risks. iPCA is an innovative technology. In addition to monitoring links, it can detect faults on cards and chips, determine packet loss locations and reasons on network nodes. On a card, all service interfaces that receive data are inbound interfaces, and all interfaces that forward data to the Switch Fabric Unit (SFU) are egress interfaces. iPCA compares the counters on inbound and outbound interfaces. If the two counters are different, packets have been lost on the card. Similarly, an interface receiving data on a chip is the inbound interface and an interface sending data is the outbound interface. iPCA compares the counters on inbound and outbound interfaces. If the two counters are different, packets have been lost on the chip. On a device, iPCA compares the counters on all inbound interfaces with the counters on all outbound interfaces to determine whether packets are lost on the device. Therefore, iPCA can detect faults on links, devices, cards, and even chips. Many scenarios will require iPCA. 2017-05-04 Huawei Proprietary - Restricted Distribution Page3, Total4 iPCA Makes Quality Awareness on IP Networks Easy INTERNAL There is another problem. Non-Huawei devices do not support iPCA. Do we need to replace all devices with Huawei devices? The answer is "no." All devices communicate with each other through IP packets. iPCA just utilizes a reserved bit in the IP packets. Customers need only deploy Huawei agile devices and iPCA on key nodes. This facilitates network reconstruction and protects customers’ investments. Basically, iPCA helps IT administrators monitor IP network quality and makes network operation and maintenance easier. 2017-05-04 Huawei Proprietary - Restricted Distribution Page4, Total4