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Ensuring A Solid DNS Foundation For VoIP

Ensuring A Solid DNS Foundation For VoIP. Anton Holleman Anton.Holleman@nominum.com October 14, 2005. Is Your Infrastructure Ready For Voice Over IP?. “It is no longer a question of whether. VoIP will wipe out traditional telephony,. but a question how quickly it will do so.”.

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Ensuring A Solid DNS Foundation For VoIP

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  1. Ensuring A Solid DNS Foundation For VoIP Anton Holleman Anton.Holleman@nominum.com October 14, 2005

  2. Is Your Infrastructure Ready For Voice Over IP? “It is no longer a question of whether VoIP will wipe out traditional telephony, but a question how quickly it will do so.” “VoIP, in short, is completely reshaping the telecoms landscape.” Economist, September 15th 2005

  3. Agenda • Nominum • Where does DNS fit in? • Modeling DNS data flow • Making DNS robust • DNS Requirements

  4. Company Focus • Commercial–grade IP name and asset management • DNS, DHCP, and IP management products • For medium to large deployments • Telco, service providers, finance, retail, government, etc. • Product leadership • Performance • Security • Management

  5. Sample Telco and Service Provider Customers

  6. Sample Enterprise and Government Customers

  7. Where does DNS fit in?

  8. What is DNS? • Foundation for services • Abstraction layer on top of addresses Mail VoIP Web DNS Network & Routers

  9. DNS From The Perspective of the Subscriber • If DNS does not work ‘the network is down’ • No call possible • A slow DNS is perceived as ‘a slow network’ • Long call set up time • Subscribers do not distinguish the network from DNS • DNS requirements for low latency and high availability

  10. Modeling DNS Data Flow

  11. DNSServers Where Does DNS Appear? ENUM DNS Service 3.DNS returns NAPTR record containing SIP URL to Calling Party UA 2.Calling party SIP server queries DNS for endpoint location Responsesip:name@domain.com Query4.3.2.1.5.5.5.2.0.2.1.e164.arpa? “Call Setup” 1.The caller dials the person’s telephone number SIPsip:name@domain.com 4.Calling party UA connects the call Dial +1-202-555-1234 SIP Server SIP Server

  12. What is ENUM? Phone Numbers in the DNS (but not just phone numbers) The best hope for an open-standards-based approach to communications identifiers and signaling for the next decade:

  13. Why multiple ENUM types? • Theory One: • The Internet wasn’t relevant until there were multiple networks. • ENUM won’t be relevant until we get a critical mass of VoIP implementations that use/need it. • Theory Two: • Its just a matter of preserving ownership/control of something valuable, e.g. • Inside an enterprise • Between partners • Outsourcing while owning • Can Internet style ENUM triumph?

  14. The Situation: Islands of VoIP Connected through the PSTN Carrier A PSTN Enterprise B Carrier C

  15. Public ENUM Carrier ENUM Private ENUM Publicly available, shared database Database shared on the basis of bi- or multi-lateral agreements Non-public database Interfaces with other CSPs ENUM OSS ENUM ENUM OSS Types of ENUM Deployments

  16. With ENUM Single Directory Infrastructure forVoice, Data, Video Why ENUM? Efficient Communications PSTN Transcoding Transcoding Network 1 Network 2 Without ENUM VOIP Phone VOIP Phone

  17. NAPTR SRV MX MD, MF Evolution of DNS data Pre and post evaluation of query and results Multiple metrics One type, separate weights, post query selection More than one type ofanswer, multiple instances

  18. Internet ENUM C B A Evolution of ENUM ? • Carrier ENUM • Public ENUM • Private ENUM

  19. Local LNP ENUM Public ENUM Public ENUM Carrier ENUM Resolver(Caching Server) Phone # in ENUM SIP Server Dial +1-202-555-1234 Phone # not in ENUM SIP Proxy PSTN ENUM Lookups Resolution ENUM Reality Ideal ENUM

  20. Making DNS Robust

  21. Updates Hidden AuthoritativePrimary Servers HighAvailability Anycast or Load Balancing Secondary Authoritative Servers Caching Servers(Resolvers) in Points of Presence ENUM Clients (SIP Proxies, Phones, etc.) Point of Presence A Point of Presence B Point of Presence C Simple High Availability Architecture

  22. Architecture Properties • Scalability • Each PoP one or more caching DNS servers • Slot in more authoritative servers if needed • Performance • Caching name server as close as possible to the subscriber • Availability • Not a single SPoF

  23. DNS Requirements

  24. Subscriber And Provider Requirements • Low latency • Fast call set up time • High availability • POTS Dial tone expectations • Large volumes of data • Millions of phone numbers • High throughput • Process thousands of calls a second • Resistance against denial of service attacks • Security • Provisioning, provisioning, provisioning, provisioning and provisioning

  25. CNS Latency Replaced BIND 9.3.1 with CNS Configuration: 1 GHz Pentium III, 512 GB of RAM, FreeBSD 4.10

  26. CNS Response Latency Configuration: Pentium III 850 MHz, 768 MB RAM, FreeBSD 4.9R

  27. All Numbersin One Zone In the Middle One Zoneper Number Private ENUM Carrier ENUM Public ENUM • Relatively easily managed • Doesn’t require vast tracts of hardware • Reduces zone size and number of zones • Handles number portability • Greatest flexibility for subscribers • Number portability is harder • Very large zone • Increases system complexity • Requires cooperation • Huge number of zones! DNS Zone Architectures Type Good For: Pros Cons

  28. Comparing BIND and Nominum ANS for ENUM Configuration: 2 X AMD 1800+ CPU at 1.5GHz, 3.5 GB RAM, 100Mb Ethernet InterfaceRed Hat Enterprise 3.0 Server

  29. High Throughput 37030 6849

  30. Why Throughput Matters • Accommodate growth number of subscribers • Denial of Service (DoS) attack disables call routing - brings phone system down

  31. Provisioning, Provisioning, Provisioning And Provisioning • Millions of phone numbers • On the fly moves adds and changes • No service down time for changes • APIs • Integrate DNS servers in your processes • Dynamic DNS • Secured through TSIG or GSS-TSIG

  32. Historical Parallel Semiconductors DNS 1947 Transistor 1983 Domain Names, RRs 1958 Integrated Circuit 1993 Dynamic update, DHCP integration 1965 Moore’s Law 2005 ?

  33. 1983 Where do I get the code for DNS to compile and install? 2005 I need a system that can do moves, adds, and changes without restarting I need to manage 100 servers as a unit I need to manage 20 system administrators I need integrated DNS and DHCP How have DNS systems changed?

  34. Conclusions • DNS is a prerequisite for VoIP • Latency and high availability matter to the subscriber • High throughput, store large volumes, security and provisioning facilities matter to the provider • Nominum implementation is ready to serve you today

  35. Thank you

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