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Introduction to Content Switch

Introduction to Content Switch. C. Edward Chow Department of Computer Science University of Colorado at Colorado Springs. Outline of the Talk. What is a Content Switch? What Services it Can Provide Content Switch Example Related Technologies Content Switch Architecture and Basic Operations

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Introduction to Content Switch

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  1. Introduction to Content Switch C. Edward ChowDepartment of Computer ScienceUniversity of Colorado at Colorado Springs

  2. Outline of the Talk • What is a Content Switch? • What Services it Can Provide • Content Switch Example • Related Technologies • Content Switch Architecture and Basic Operations • TCP Delay Binding and Related Improvement • Content Switch Rule and Conflict Detection • Related Load Balancing Research Results Edward Chow ACSD Project Status 2

  3. Content Switch (CS) • Route packets based on high layer (Layer 5/7) headers and content. • Examples: • Direct Web traffic based on pattern of URLs, host tags, cookies. • Can Route incoming email based on email address;Connect POP/IMAP based on login • Web switches and Intel XML Director/accelerator are special cases of content switch. Edward Chow ACSD Project Status 3

  4. What Services It Can Provide • Enabling premium services for e-commerce, ISP, and Web hosting providers • Load Balancing and High Available Server Clusters: Web, E-commerce, Email, Computing, File, SAN • Policy-based networking, differential/QoS services. • Firewall, Strengthening DoS protection, cache/firewall load-balancing • ‘Flash-crowd' management • Email Spam Protection, Virus Detection/Removal • Applet Authentication/Filtering Edward Chow ACSD Project Status 4

  5. Site II losangeles.domain.com Internet Internet Site I newyork.domain.com Router 3-DNS BIG-IP BIG-IP Local DNS GLOBAL-SITE Webmaster Site III tokyo.domain.com Server Array User london.domain.com F5 VRM Solution Edward Chow ACSD Project Status 5

  6. Intel Netstructure XML Director 7280 • Example of Rule:Server1: create */order.asp & //Amount[Value >= 10000] Edward Chow ACSD Project Status 6

  7. Phobos In-Switch • Only load balancing switch in a PCI card form factor • Plugs directly into any server PCI slot • Supports up to 8,192 servers, ensuring availability and maximum performance • Six different algorithms are available for optimum performance: Round Robin, Weighted Percentage, Least Connections, Fastest Response Time, Adaptive and Fixed. • Provides failover to other servers for high-availability of the web site • U.S. Retail $1995.00 Edward Chow ACSD Project Status 7

  8. E-Commerce Example: 1. Client Client submits via HTTP/Post (or SOAP) the following purchase in XML: <purchase> <customerName>CCL</customerName> <customerID>111222333</customerID> <item><productID>309121544</productID> <productName>IBM Thinkpad T21</productName> <unitPrice>5000</unitPrice> <noOfUnits>10</noOfUnits> <subTotal>50000</subTotal> </item> <item><productID>309121538</productID> <productName>Intel wireless LAN PC Card</productName> <unitPrice>200</unitPrice> <noOfUnits>10</noOfUnits> <subTotal>2000</subTotal> </item> <totalAmount>52000</totalAmount> </purchase> Edward Chow ACSD Project Status 8

  9. E-Commerce Example: 2. Content Switch • Content switch receives the packet. • Recognize it is a http post request from http request line POST /purchase.cgi HTTP/1.1 • Recognize it is an XML document from the meta headercontent-type: TEXT/XML • Parsing XML content • Extract values of tag sequences:52000purchase/totalAmountCCLpurchase/customerName • Rule 1 is matched and packet is routed to one of highSpeedServers.Rule 1:if (xml.purchase/totalAmount > 5000) routeTo(highSpeedServers);Rule 2: if (xml.purchase/customerName == CCL) routeTo(specialCustomerServers); Edward Chow ACSD Project Status 9

  10. No Free Lunch:Penalty of Having Content Switch •  Increased packet processing time. • For XML Director/Accelerator, it needs to parse XML document and match tag sequences. 1-3? order of processing time Edward Chow ACSD Project Status 10

  11. Related Technologies • Application level solution: Proxy server; Apache/Tomcat/Servlet; Microsoft NLB • Kernel level layer 4 load balancing solution: http://www.linuxvirtualserver.org/ • Joseph Mark’s presentation • LVS-NAT(Network Address Translation) web page • LVS-IP Tunnel web page • LVS-DR (Direct Routing) web page • Hardware solution: Cisco 11000, F5 (Big IP), Alteon Web Systems, Foundry Networks (ServerIron),Good information: Foundry ServerIron Installation and Configuration Guide, May 2000. Edward Chow ACSD Project Status 11

  12. Basic Operations of Content Switching CS: Content Switching CS RuleEditor CS Rules Incoming Packets Packet Classification Header ContentExtraction CS Rule Matching Algorithm Forward Packet To Servers Packet Routing(Load Balancing) Network Path Info Server Load Status Edward Chow ACSD Project Status 12

  13. Content Switch Architecture Apostolopoulos 2000 Edward Chow ACSD Project Status 13

  14. Efficient Software Architecture • Tasks: Million Packets with thousand of rules to match and load balancing algorithms to run. • How to assign tasks to the processors and threads? • Packet Extraction (Understand header formats, XML parsing) • Content Switching Rule Matching • Packet Routing (Load Balancing, Bandwidth Control) • How Much Packet Processing Should Controllers Do? • What a controller can do? • A Typical Parallel Processing Problem? Edward Chow ACSD Project Status 14

  15. step3 ACK(DSEQ+1) DATA(CSEQ+1) DATA(?) 2nd request ACK(DSEQ+1) ACK(?) TCP Delay Binding client server content switch SYN(CSEQ) step1 SYN(DSEQ) step2 ACK(CSEQ+1) step4 SYN(CSEQ) step5 SYN(SSEQ) step6 ACK(CSEQ+1) step7 ACK(SSEQ+1) step8 DATA(CSEQ+1) ACK(SSEQ+1) DATA(DSEQ+1) DATA(SSEQ+1) step9 ACK(CSEQ+LenR+1) ACK(CSEQ+lenR+1) step10 ACK(DSEQ+ lenD+1) ACK(SSEQ+lenD+1) step11 lenR: size of http request. . lenD: size of return document Edward Chow ACSD Project Status 15

  16. Lesson Learned in Implementing TCP Delay Binding • In our Linux 2.2 kernel-based content switch prototype, we found client sends duplicate requests after step 3. • It overloads the content switch and the real server. • Reason: • Client TCP time-out, retransmit • Content switch printk() overhead, too many debug msgs • It could happens when there are many content rules, slow server response. • Solution: content switch sends ack(CSEQ+LenR+1) to stop retransmit. Edward Chow ACSD Project Status 16

  17. SYN(CSEQ) SYN(CSEQ) step1 SYN(SSEQ) SYN(SSEQ) step2 ACK(CSEQ+1) ACK(CSEQ+1) step3 DATA(CSEQ+1) DATA(CSEQ+1) ACK(SSEQ+1) ACK(SSEQ+1) step4 DATA(SSEQ+1) DATA(SSEQ+1) ACK(CSEQ+LenR+1) ACK(CSEQ+lenR+1) step5 lenD+1) ACK(SSEQ+ ACK(SSEQ+lenD+1) Pre-Allocate Server Scheme Pre-allocated server client content switch • Guess routing decision based on IP/Port#/History • Advantage: • Faster than TCP delay binding. • Possible direct route between client and server • Reduce session processing overhead no need to convert server sequence # . Edward Chow ACSD Project Status 17

  18. SYN(CSEQ) step4 SYN(RSEQ) step5 ACK(CSEQ+1) step6 DATA(CSEQ+1) ACK(SSEQ+1) Degenerated to TCP Delay Binding If Guess Wrong Pre-allocated server client content switch SYN(CSEQ) SYN(CSEQ) step1 SYN(SSEQ) SYN(SSEQ) step2 ACK(CSEQ+1) ACK(CSEQ+1) step3a DATA(CSEQ+1) FIN(CSEQ+1) ACK(SSEQ+1) Right server step4 DATA(SSEQ+1) DATA(RSEQ+1) ACK(CSEQ+LenR+1) ACK(CSEQ+lenR+1) step5 lenD+1) ACK(DSEQ+ ACK(SSEQ+lenD+1) Sequence # conversion needed Edward Chow ACSD Project Status 18

  19. Filter Process Scheme Filter Processrun on server client server content switch SYN(CSEQ) step1 SYN(DSEQ) step2 ACK(CSEQ+1) DATA(CSEQ+1) step3 ACK(DSEQ+1) step4b Migrate(Data, CSEQ, DSEQ) SYN(CSEQ) step4 a SYN(SSEQ) step5 ACK(CSEQ+1) step6 DATA(CSEQ+1) ACK(SSEQ+1) step7 DATA(DSEQ+1) DATA(SSEQ+1) ACK(CSEQ+LenR+1) ACK(CSEQ+lenR+1) step8 ACK(DSEQ+ lenD+1) ACK(SSEQ+lenD+1) Edward Chow ACSD Project Status 19

  20. Multiple HTTP Requests from One TCP Connection NAT approach server1 home.htm ContentSwitch server2 client . . uccs.jpg Index.htm . rocky.mid server9 • A keep alive TCP connection may include multiple HTTP “GET” requests. • Content Switch examines each “GET” request and makes new routing decision. • Content Switch establishes another connection with a different server based on the routing decision. • Those HTTP responses from different servers need to be interleaved and seen by the user as if from the same server. • Solutions: In order delivery (buffer requirement); Out of order delivery (seq# tracking)? • Problems: Should we throw away earlier html requests if receive later requests? Edward Chow ACSD Project Status 20

  21. Multiple HTTP Requests from One TCP Connection server1 home.htm • Can servers return documents directly to client in keep-alive session case? • Can equivalent VS-Tunnel or VS-DR be implemented using Content Switch? ContentSwitch server2 client . . . server9 rocky.mid uccs.jpg Edward Chow ACSD Project Status 21

  22. Content Switch Rule Survey Survey shows that existing switches support • rules in basic (condition action) or (action condition) form • some define condition as class, then specify the action in separate statement or command • simple single conditional term • command line interface (to facilitate incremental update?) • Actions can include reject, forward, put in queue (for bandwidth control, scheduling) Edward Chow ACSD Project Status 22

  23. Content Switch Rule Design • Rule syntax generic to support all Intended features. • Use simple C if statement syntax rule: if (condition) { action } • Easy to read • Allow optimization using c compiler • Condition consists of multiple terms of • variable relational_operator valuee.g. xml.purchase/totalAmount > 50000 smtp.to == “chow@cs.uccs.edu” cookie.name == “servlet1” bitmatch(64, 8, 0xff) == 64 # above mean TTL=64 idea from netfilter universal filter • suffix(variable, string) e.g. suffix(url, “gif”) • regex(variable, pattern) e.g. regex(url, “/purchase”) • Action consists of reject, forward(server| queue)loadBalance(serverGroup, loadBalancingAlgorihtm) Edward Chow ACSD Project Status 23

  24. Efficient CS Rule Matching • Brute force, strict priority: Rules are executed in sequential manner. • Efficient Rule Matching Method: • Organize Rules so that rules can be skipped based on existing content types. • Utilize compiler optimization technique. Edward Chow ACSD Project Status 24

  25. Simple CS Rule Editor GUI Edward Chow ACSD Project Status 25

  26. Conflict Detection on Content Switching Rules • Detect conflicts among rules or rule set. • Absolute conflict type: r1: if (xml.purchase/customerName == “CCL”) {routeTo(r1)}r2: if (xml.purchase/customerName == “CCL”) {routeTo(r2)} • Potential conflict type: r1: if (xml.purchase/totalAmount > 5000) {routeTo(quickServers)}r2: if (xml.purchase/totalAmount >20000) {routeTo(superServers)} • Algorithm: Build tree with the same variable, check operator and value to see if they are the same or lead to potential conflict, compare actions to decide conflict type or duplication. • Editor can build these trees while a user enters rules and warns about conflict right away. Edward Chow ACSD Project Status 26

  27. XML Tag Value Extraction • A xmlContentExtract() is built to extract the tag values of a list of unique tag sequences. • It is based on clark cooper’s expat 1.0 xmlparser. • Its argument include the pointer to an XML document, the pointer to the array of strings (unique xml tag squences we follow the xsl selector syntax), and the number of sequences. • It return the list of a structure node, with the tag sequence, its attribute, and its value. • Currently, it supports one attribute and tag sequece needs to be unique. Edward Chow ACSD Project Status 27

  28. Status of UCCS ACSD Project • A Linux-based content switch prototype is almost complete. • It is based on Linux-2.2.16-3 and lvs. • ip_forward.c, ip_masq.c, ip_vs.c are modified to implement basic TCP delay binding. • Preliminary tests had real server return web document and discovered the client retransmission problem. • ip_cs.c are added for most of the content switching functions. • http header extraction and xml content extract code are being integrated in for testing. • A simple Java-based ruleEdit program was created for rule editing. Edward Chow ACSD Project Status 28

  29. Related Load Balancing Research Results • Modified Apache status module to report • Total bytes to be transferred by child processes • Average document transfer speed • Modified LB-DNS to receive server status and bandwidth probing results. • LB-DNS returns IP-address of the best server based a weight contributed by both server load and bandwidth. • Modified WebStone benchmark to test the performance of load balancing web server clusters. Edward Chow ACSD Project Status 29

  30. Load balancing Systems Bandwidth Probe Results Modified Web Server 1 Statistics Gathering Daemon Server Delay Server Ranking /tmp/StatFile Modified Web Server n LBA: Modified DNS Request for Web pages Edward Chow ACSD Project Status 30

  31. Connection Rate: LBA vs. Round-Robin Round robin only run once Edward Chow ACSD Project Status 31

  32. Conclusion • Content switch with generic rules can be easily configured for wide-variety of value-added services: • Load balancing/High Available server farm. • Premium services • Firewall • Bandwidth control/Traffic shaping • Require efficient SW/HW architecture and rule matching algorithms to reduce processing overhead. • Content rule design/conflict detection are important and challenging. • TCP delay binding can be improved. • Servicing multiple requests in keep alive session introduces interesting problem. Edward Chow ACSD Project Status 32

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