1. April 10, 2006, Northwestern University
eXCP ExCP
Offense by Amit
April 10, 2006, Northwestern University

2. Congestion Control Design Space
End Point
Router Support
Try and
Backoff
TCP, Vegas, RAP,
Fast TCP, S-TCP
High Speed TCP
DecBit, ECN,
RED, AQM
Request
and Set
PCP
ATM, XCP,
WFQ, RCP

3. Deployment Not end-to-end solution
Modification required in routers
Anderson et. al. PCP:Efficient Endpoint Congestion control
Incremental deployment is infeasible
All routers must be XCP enabled
What if bottleneck router is not XCP enabled?
Loss due to congestion but XCP assumes otherwise

4. Performance Comparison with TCP-Reno instead of TCP-SACK, TCP-Vegas
Only Simulation based evaluation
Limitation of sender buffer/receiver window
How useful is for short web-traffic?
Congestion avoidance vs slow-start

5. Security Sender Centric vs Receiver Centric Fake H_rtt
Fake H_cwnd (H_throughput)
Discard H_feedback
Compromised/Misbehaving Router
Can completely shut-off good flows

6. Contribution Stoica's CSFQ: Core Stateless Fair Queuing (SIGCOMM '98)
Edge routers – per flow management, rate estimation (r)
Core routers – fair allocation of bandwidth among flows (f)
Each packet of a flow with arrival rate r is forwarded with probability p = min(1, f/r)
Core routers estimate fair allocation of b/w using iterative algorithm
XCP – modification of CSFQ, worse from the perspective that it cannot detect misbehaving hots nor can do policy enforcement