Link Scheduling
Challenge: Tspec may change at exit of scheduler (e.g., FCFS) because of interactions among flows
FCFS increases worst-case delay and jitter, so we admit less flows
Solution: non-FCFS scheduler that isolates different flows or classes of flows (hard, soft, best-effort)
Emulate TDM without wasting bandwidth
Virtual Clock provides flows with throughput guarantees and isolation
Idea: use logical (rather than real) time
AR: average data rate required by a flow
When a packet of size P arrives, VC = VC + P/AR
Transmit packets in increasing order of time stamps
If a flow has twice AR, it will get double a double rate