1. SUPE 20071 z2z: Discovering Zeroconf Services Beyond Local Link Jae Woo Lee, Henning Schulzrinne Columbia University Wolfgang Kellerer, Zoran Despotovic DoCoMo Communications Laboratories Europe Presented by Jae Woo Lee

2. SUPE 20072 Outline Motivation Background: Zeroconf, DNS-SD, mDNS, Bonjour z2z overview Demo: global iTunes sharing How z2z works: step-by-step walk-through Implementation Related work Future work

3. SUPE 20073 Motivation Zeroconf dominates local service discovery today –Easy to use –Based on proven technology (DNS) –Widespread support by applications and devices –But it only works within a subnet! Can we use Zeroconf beyond local link? –Extend the reach of existing applications –Transient service discovery on the Internet Structured peer-to-peer network of Zeroconf subnets!

4. SUPE 20074 Zeroconf, mDNS, DNS-SD, and Bonjour IETF Zero Configuration Networking Working Group identified three requirements: 1)IP address assignment without a DHCP server 2)Host name resolution without a DNS server 3)Local service discovery without any rendezvous server Solutions: –RFC3927: Link-local addressing standard for 1) –DNS-SD/mDNS: Apple’s protocol for 2) & 3) –Bonjour: DNS-SD/mDNS implementation by Apple –Avahi: DNS-SD/mDNS implementation for Linux and BSD Many use “Zeroconf” to mean DNS-SD/mDNS

5. SUPE 20075 DNS-SD/mDNS overview Multicast DNS (mDNS) –Runs on each host in a local subnet –Queries & answers are sent via link-local multicast to port 5353 –Special TLD reserved for local names: “.local.” DNS-Based Service Discovery (DNS-SD) –PTR records enumerate available service instances _daap._tcp.local. PTR Tom’s Music._daap._tcp.local. _daap._tcp.local. PTR Joe’s Music._daap._tcp.local. –SRV & A records resolve a specific service instance Tom’s Music._daap._tcp.local. SRV 0 0 3689 Toms-machine.local. Toms-machine.local. A 160.39.225.12 –TXT records contain additional information Tom’s Music._daap._tcp.local. TXT "Version=196613" "iTSh Version=196608" "Machine ID=6070CABB0585" "Password=true”

6. SUPE 20076 z2z: Zeroconf-to-Zeroconf interconnection OpenDHT z2z Import/export Services Zeroconf subnet A z2z Import/export Services Zeroconf subnet B

7. SUPE 20077 Demo: global iTunes sharing Exporting iTunes shares under key “columbia”: $ z2z --export:opendht _daap._tcp --key “columbia” Importing services stored under key “columbia”: $ z2z --import:opendht --key “columbia”

8. SUPE 20078 How z2z works (exporting) OpenDHT z2z Send browse request (i.e., PTR query) for service type: _daap._tcp 1) Tom’s Music. _daap._tcp.local Joe’s Music. _daap._tcp.local Send resolve request (i.e., SRV, A, and TXT query) for each service 2) 160.39.225.12:3689 Password=true …… 160.39.225.13:3689 Password=false …… Export them by sending put messages to OpenDHT 3) put: key= z2z.opendht.columbia value= Tom’s Music 160.39.225.12:3689 Password=true ……

9. SUPE 20079 How z2z works (importing) OpenDHT z2z Issue a get call to OpenDHT 1) Import services by registering them (i.e., add PTR, SRV, A, TXT records to the local mDNS) 2) get: key=z2z.opendht.columbia value=Tom’s Music 160.39.225.12:3689 …… value=Joe’s Music …… _daap._tcp.local. PTR … Tom’s Music._daap._tcp.local. SRV … Tom’s Music._daap._tcp.local. TXT … _remote-160.39.225.12.local. A …

10. SUPE 200710 Implementation C++ Prototype using xmlrpc-c for OpenDHT access –Porting problem due to Bonjour and Cygwin incompatibility z2z v1.0 released –Rewritten in Java from scratch –Open-source (BSD license) –Available in SourceForge ( https://sourceforge.net/projects/z2z) https://sourceforge.net/projects/z2z

11. SUPE 200711 Related work Wide-area Bonjour –Apple’s solution for Zeroconf beyond local link –Use conventional unicast DNS instead of mDNS –Need to setup and maintain DNS server Rendezvous Proxy –GUI interface for proxy registration of remote service LogMeIn Hamachi –Virtual LAN connectivity over the Internet Simplify Media –iTunes sharing on a social network P2P Networking in Windows Vista

12. SUPE 200712 Future work Study on scalability of Zeroconf network –mDNS traffic imposes burden on large wireless network –Does z2z make it worse? To what extent? –Possible improvement in z2z: importing to local host only Usability improvement –GUI interface –NAT traversal Beyond OpenDHT –Better searching Distributed hierarchical index Query-capable DHT or p2p search engine technology –z2z on a social network iTunes sharing on Facebook

13. SUPE 200713 Thank you.