Midterm Midterm 200 soft 150 L7 100 web leases 50 TCP 0 1 - - PowerPoint PPT Presentation

Midterm Midterm

50 100 150 200 1 3 5 7 9 11 13 15 17 19 21 23 soft L7 web leases TCP

Problem 1 Problem 1

• Why OK with HTTP 1.0

LARD or L7: route connection by URL or SLB at SYN DNS (Akamai): route at connection setup by domain name

• Why OK with NFS/UDP

every request/reply an independent packet, so can route these independently

• HTTP 1.1 and NFS: persistent connections

can’t route request/reply on the same stream independently

• No effect on Akamai
• If route requests on connection grain, L7 or LARD will lose

locality.

Leases Leases

1) overhead vs. recovery time

not callback time (-3)

2) server grabs lease if on wrong side of partition.

• reject writes

e.g., timestamp writes and reject at target

3) failover, wait lease interval

clients renew need failure detector and group membership could use quorum

Large Large-

• Scale Web Caching

Scale Web Caching

• explain basic mechanism
• larger populations for same hit rate, + flatter curve
• ignoring deemphasizes benefit of cooperative caching

100% cacheable hit rate with sufficiently large cache

• effect of popularity (5 points)
• say something about traces (5 points)

URL Hashing URL Hashing

LAN

• good locality ==> good caching, less storage needed
• possibility of unbalance
• simple switch
• failure/reconfig issue (+ or -)
• Alternative: e.g., LARD

WAN

• see above
• one hop, but no geo-locality (5)
• alternative: summary cache