24-04-2012, 12:19 PM
GFR -- Providing Rate Guarantees with FIFO Buffers to TCP Traffic
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Guaranteed Frame Rate (GFR)
GFR guarantees:
Low loss ratio to conforming frames
Best effort to all frames
Fair share of unused capacity
(Not well defined. May be removed.)
User specifies an MCR and a maximum frame size
Conforming Frames = Frames which are untagged
by the end system and pass the GCRA like policing
mechanism.
GFR Implementation Issues
FIFO queuing versus per-VC queuing
Per-VC queuing is too expensive.
FIFO queuing should work by setting thresholds
based on bandwidth allocations.
Network tagging and end-system tagging
End system tagging can prioritize certain cells or
cell streams.
Network tagging used for policing -- must be
requested by the end system. [?]
Buffer management policies
Per-VC accounting policies need to be studied
Summary
SACK TCP throughput may be controlled with
FIFO queuing under certain circumstances:
TCP, SACK (?)
S MCRs < Uncommitted bandwidth
Same RTT (?), Same frame size (?)
No other non-TCP or higher priority traffic