Bits & bytes

1. Bits & bytes Network protocols Stephen Kershaw Network Protocols | Stephen Kershaw

2. Multicast • Use for distributed correlation • Save bandwidth over wide-area routed networks • From telescopes to processing/storage clusters • Considerations • Multicast availability and configuration • From wide-area networks • End hosts • Use of uniform/compatible multicast technology Network Protocols | Stephen Kershaw

3. Multicast • Test of multicast topology • Multicast UDP stream over JANET academic network • IPTV originating from London UK • 100 2.2Mbps multicast streams • End-hosts on Manchester University campus network • All Cisco network hardware • 100Mbps interfaces, line-rate throughput from London based unicast hosts • Measurement of inter-packet arrival times • Time from arrival of packet ‘n’ to arrival of packet ‘n+1’ • ~6ms for one 2.2Mbps stream Network Protocols | Stephen Kershaw

4. Latency spikes of up to 0.5s at intervals of 60s Network Protocols | Stephen Kershaw

5. Correlation between streams and between PCs Network Protocols | Stephen Kershaw

6. Multicast • Test of multicast topology • Multicast traffic routing is not as efficient as unicast on this network • Concerns for other networks Network Protocols | Stephen Kershaw

7. DCCP • Stable kernel • 2.6.23 • Still require tuning of virtual memory settings to prevent kernel panics • Experimental kernels • Revisions of late November 2007 address some memory issues – yet to be tested on our systems • Many revisions to CCID3, few to CCID2 • CCID4 in development • Performance • CCID2 can attain 1GE line-rate butit is not a turn-key thing Network Protocols | Stephen Kershaw

8. Network admin • Scheduling usage • Local, metro, national, international connections between: • Telescopes, correlator, IBOBs, PCs • For testing equipment, networks, software • Do we need local admin (MRBS) or wider? • Monitoring performance • Can redeploy ESLEA system Network Protocols | Stephen Kershaw

9. Network Protocols | Stephen Kershaw