F5 White Paper Sessio Iitiated Protocol (SIP) ad Message-based Load Balacig (MBLB) The ability to provide ew ad creative methods of commuicatios has esured a SIP presece i almost every orgaizatio. The use of message-based load balacig offers the ability to aggregate ad disaggregate SIP messagig, ad prevets message-blockig asymmetric server retur. By Paul Stalvig Techical Marketig Maager
Sessio Iitiated Protocol (SIP) ad Message-based Load Balacig (MBLB) Cotets Itroductio 3 SIP Commuicatios 3 Aggregatio/Disaggregatio 4 TLS Offload 4 Message-based Load Balacig 4 Blockig 5 Locatio 5 Coclusio 6 2
Sessio Iitiated Protocol (SIP) ad Message-based Load Balacig (MBLB) Itroductio At the service provider level, the umber of VLAN, TCP (or UDP) port, ad IP triplet combiatios is affectig the Sessio Iitiated Protocol (SIP). Betwee servers, where the VLAN, TCP port, ad IP variatios are limited, the ephemeral ports are costatly beig pushed ad overru. Because of active SIP subscriber couts i the millios, the potetial to use various combiatios of IP addresses ad ephemeral ports is ot realistic. Providig a method to aggregate ad disaggregate these commuicatios ito a sigle triplet or as a idividual stream of iformatio eables greater scalability, performace, ad reliability, ad relieves the strai caused by these limitatios. Eve with the use of IPv6 IP addresses, the IP address limitatio is ofte foud betwee the SIP proxy ad SIP server, because aggregatig commuicatios provides performace advatages that outweigh the relief of IPv6 triplet combiatios. Aggregatio is the combiig of multiple commuicatios withi a sigle stream coectio. Disaggregatio is the separatio of the commuicatios from the stream coectio. The aggregatio ad disaggregatio of SIP commuicatios ca lead to improved user experieces ad icreased average reveue per user (ARPU), while simultaeously decreasig or elimiatig dowtime. The eed to icrease performace ad decrease bottleecks i IP Multimedia Subsystem (IMS), Service Delivery Platform (SDP), ad Voice over IP (VoIP) architectures has grow with the icrease i availability ad adoptio of applicatios that use SIP. SIP Commuicatios As commuicatios protocols coverge o IP, they ca create issues at the etwork level. SIP is o exceptio. With iheret asychroous routig ad the eed for cotiual updatig of log-lastig commuicatios, the impact of SIP o the etwork is oly ow beig fully uderstood. But, SIP broades user capabilities ad, cosequetly, improves the user experiece. By eablig more devices (laptop, cell phoe, PDA, etc.), to establish, maitai, ad improve commuicatios, user experiece improves. I order to maitai commuicatios, most implemetatios of SIP are, at best, chatty. This chattiess ca rage from simple updates durig commuicatios to the complete floodig of etworks with commuicatios cotrol ad reportig. At first glace, it would seem that reducig the chattiess of SIP could solve may issues; however, this ca ultimately degrade the user experiece. Oe of the reasos that SIP ca become chatty is that the actual SIP commuicatios do ot always follow the same etwork path as their associatio. Routers BIG-IP Local Traffic Maager SIP Servers Cotrol Chael Data Chael Figure 1: Asychroous Routig 3
Sessio Iitiated Protocol (SIP) ad Message-based Load Balacig (MBLB) Asychroous routig is ofte see as a flaw i SIP, but it actually ca remove cotrol (or sigalig) of iformatio from affectig the data (or voice) chael iformatio. By performig the separatio of cotrol iformatio from the data chael iformatio, the SIP servers are better positioed to provide aalysis ad performace iformatio to improve the data chael stream ad ultimately esure a good user experiece. Ultimately, without the SIP (cotrol chael) chattiess, the data chael could be lost ad would ot recoect. Ay message withi SIP must belog to the commuicatios betwee a user device ad the server. Whe multiple SIP servers are used, the all of the correspodig messages must be set to the correct SIP server for them to have ay effect. This icludes the coectio performace details from the commuicatios, such as cotrol-chael data (as see i Figure 1). The SIP ad cotrol-chael data (oted i black) would flow from the devices to the SIP server, whereas the data-chael iformatio (oted i gree) would flow betwee the devices ad their routers without goig to the server. Aggregatio/Disaggregatio F5 BIG-IP Local Traffic Maager (LTM) ca provide aggregatio/disaggregatio of the coectios to the SIP servers usig TCP, TLS/TCP, UDP, or SCTP. This eables the SIP servers to perform operatios o the iformatio i the coectio without the overhead of umerous smaller coectios. Aggregatio/disaggregatio improves the sessio s setup time ad eables SIP servers ad proxies to focus o their primary purpose istead of maagig the umerous coectios. The reductio ca provide icreased performace ad delay the eed for additioal servers. Whe it becomes ecessary to icrease servers, F5 BIG-IP LTM eables health-checkig of ay ew device to esure proper fuctioality. TLS Offload BIG-IP LTM ca also provide icreased SIP server performace by termiatig TLS/ SSL sessios. By usig hardware-accelerated ecryptio, the BIG-IP is better able to hadle the workload of ecryptig ad decryptig the sessios. The trasport layer security (TLS) offloadig fuctio improves SIP server performace by 50 percet. SIP Proxy SIP Server Icreased Capabilities SIP Proxy BIG-IP Local Traffic Maager Message-based Load Balacig SIP commuicatios use a message-based cotext of commuicatios. The ability to perform load balacig of idividual messages is referred to as message-based SIP Servers Figure 2: Aggregatio 4
Sessio Iitiated Protocol (SIP) ad Message-based Load Balacig (MBLB) load balacig (MBLB). Because SIP is used for voice commuicatios, sessios must be persisted for the duratio of the coversatio. This requires that the coectio betwee the cliet device ad the SIP server must be persisted or the commuicatio chael will fail. SIP cotrol chael coectios ca pass very little data from the server to the cliet durig high-quality commuicatios. If the data chael commuicatios experiece some form of degradatio, the the cotrol chael commuicatios will pass messages back ad forth to re-establish the proper quality of service. This quality is directly related to the user experiece. BIG-IP LTM SIP message-based load balacig provides a message-by-message look withi the SIP commuicatios to determie ad maitai the correct clietserver coectios. I smaller orgaizatios this may ot be a problem; The BIG-IP LTM ca simply persist based o a source IP address. I the service provider space there ca be thousads of coectios origiatig from a sigle IP address. BIG-IP LTM load balaces SIP commuicatios accurately eve if they are aggregated ito a TCP, UDP, or SCTP stream by readig the SIP messages oe at a time. Stream 1 Stream 2 Stream 3 Stream... Figure 3: Oe TCP coectio cotaiig multiple SIP sessios Blockig Normally associated with TCP, queuig or call-flow blockig, occurs whe oe piece of iformatio eeds to be retrasmitted ad causes all subsequet iformatio to wait, pedig the receipt ad ackowledgemet of the lost iformatio. While i most etwork commuicatios eviromets this does ot cause egative issues, the delays caused by blockig i SIP ca mea the differece betwee a positive ad a egative user experiece. By usig a multi-stream costruct, withi the SIP aggregatio, as show i Figure 3, BIG-IP LTM is able to cotiue processig commuicatios without waitig for a respose from the first sessio. Oly the commuicatios stream that is affected would be blocked; the other commuicatios streams would cotiue to flow. Locatio Each service provider will have differet requiremets for the architectural locatio for the ew capabilities. However, with the icreased advatages of usig BIG-IP LTM SIP message-based load balacig to cotrol the performace of critical coectivity, the locatio i the architecture becomes easier. For example, oe carrier may eed to provide the beefits betwee the Call Sessio 5
Architectig Highly Available ESB Services A Healthier, Happier SOA Cotrol Fuctio (CSCF) ad the Sessio Border Cotrol (SBC). Aother carrier eeds to be able to provide the fuctioality withi the CSCF betwee the Iterrogatig, Proxy, ad Servig CSCFs. Both carriers could also use the SIP message-based load balacig ad BIG-IP LTM capabilities to provisio the key beefits betwee the cotrol layer CSCF ad the applicatio servers i the IMS ifrastructure. Coclusio Key Beefits Icrease user capabilities Icrease user experiece Icrease Average Reveue Per User (ARPU) Provide a measuremet ito user experiece Provide performace statistics The F5 s message-based load balacig esures a good user experiece by maitaiig the coectio from the user s device to the server. If the direct commuicatios are ot performig correctly, the server ca immediately step i ad re-establish itself as the hub for the commuicatios, esurig that the user experiece ad performace levels are maitaied. F5 BIG-IP Local Traffic Maager ca help orgaizatios aalyze the SIP commuicatios to determie curret ad future etwork ad system performace eeds. BIG-IP LTM ca also esure that the SIP server is ruig properly by implemetig various health checks. Before a additioal SIP server is activated, the server must pass a health check. This eables SIP services to expad without dowtime. The ability to provide ew ad creative methods of commuicatios has esured a SIP presece i almost every orgaizatio. The use of message-based load balacig offers the ability to aggregate ad disaggregate SIP messagig, ad prevets message blockig asymmetric server retur. BIG-IP LTM ca improve user experiece, icrease the user s device lists ad capabilities, ad provide a direct lik to average reveue per user. BIG-IP LTM eables growth ad performace aalysis while elimiatig dowtime. Icrease performace of SIP servers usig (dis)aggregatio with TCP, TLS over TCP, UDP, ad SCTP Icrease capabilities without dowtime Icrease SIP server capacity Decrease SIP sessio setup/ teardow time Itegrate ito existig ad future routig methods, usig RIP, BGP, OSPF, ad IS-IS whether it is IPv4 or IPv6 F5 Networks, Ic. Corporate Headquarters 401 Elliott Aveue West Seattle, WA 98119 +1-206-272-5555 Phoe (888) 88BIGIP Toll-free +1-206-272-5556 Fax www.f5.com ifo@f5.com F5 Networks Asia-Pacific +65-6533-6103 Phoe +65-6533-6106 Fax ifo.asia@f5.com F5 Networks Ltd. Europe/Middle-East/Africa +44 (0) 1932 582 000 Phoe +44 (0) 1932 582 001 Fax emeaifo@f5.com F5 Networks Japa K.K. +81-3-5114-3200 Phoe +81-3-5114-3201 Fax ifo@f5etworks.co.jp WP-SIP-MBLB 05/08 2008 F5 Networks, Ic. All rights reserved. F5, F5 Networks, the F5 logo, BIG-IP, VIPRION, FirePass, ad icotrol are trademarks or registered trademarks of F5 Networks, Ic. i the U.S. ad i certai other coutries. 6