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1、Ph.D. Thesis Presentation Aleksandar Kuzmanovic,Edge-based Inference, Control, and DoS Resilience for the Internet,The Internet,1969,The system of astonishing scale and complexity,2004,Internet Design Principles,Network as a black-box,End-to-end argument Clark84 The core is simple Intelligence at th
2、e endpoints,Implications Easy to upgrade the network Easy to incrementally deploy new services,Why End-Point Approach Today?,Scalability e2e scalability Deployability IP and network core are not extensible and are slowly evolving: IPv6 (10 years) IP Multicast (domain dependent),Goal: Improve network
3、 performance right here right now!,Network Performance,Internet traffic HTTP (web browsing) FTP (file transfer) Fact: 95% of the traffic today is TCP-based Performance QoS differentiation Net win for both HTTP and FTP flows End-point-based two-level differentiation scheme Denial of Service DoS attac
4、ks can demolish network performance Prevent DoS attacks via a robust end-point protocol design,End-Point Service Differentiation,TCP-Low Priority Utilizes only the excess network bandwidth Key mechanism Early congestion indications: one-way packet delay Performance Can improve the HTTP file transfer
5、s for more than 90% when FTP flows use TCP-LP Deployability no changes in the network core sender side modification of TCP High-speed version developed in cooperation with SLAC tested over Gb/s networks in US http:/www.ece.rice.edu/networks/TCP-LP,Denial of Service,A malicious way to consume resourc
6、es in a network, a server cluster or in an end host, thereby denying service to other legitimate users Example Well-known TCPs vulnerability to high-rate non-responsive flows,Design Principles - Revisited,Design Principles Intelligence at the endpoints The core is simple Trust and cooperation among
7、the endpoints,Implications Easy to incrementally implement new services,. Easy to upgrade the network,. Large-scale system,Implement more intelligence at routers? Scalability issue Detect misbehaving flows in routers is a hard problem Needle in a haystack,Design Principles - Revisited,Design Princip
8、les Intelligence at the endpoints The core is simple Trust and cooperation among the endpoints,Implications Malicious clients may misuse the intelligence,. Easy to upgrade the network,. Large-scale system,Implement more intelligence at routers? Scalability issue Detect misbehaving flows in routers i
9、s a hard problem Needle in a haystack,Design Principles - Revisited,Design Principles Intelligence at the endpoints The core is simple Trust and cooperation among the endpoints,. Hard to detect endpoint misbehavior,. Large-scale system,Malicious clients may misuse the intelligence,Implications,Imple
10、ment more intelligence at routers? Scalability issue Detect misbehaving flows in routers is a hard problem Needle in a haystack,Design Principles - Revisited,Design Principles Intelligence at the endpoints The core is simple Trust and cooperation among the endpoints,. Hard to detect endpoint misbeha
11、vior,. Large-scale system,Malicious clients may misuse the intelligence,Implications,Implement more intelligence at routers? Scalability issue Detect misbehaving flows in routers is a hard problem Needle in a haystack,End-Point Protocol Design,Performance vs. Security End-point protocols are designe
12、d to maximize performance, but ignore security 95% of the Internet traffic is TCP traffic Can have catastrophic consequences DoS-resilient protocol design Jointly optimize performance and security Outperforms the core-based solutions,Remaining Outline,End-point protocol vulnerabilities Low-rate TCP-
13、targeted DoS attacks Receiver-based TCP stacks with a misbehaving receiver Limitations of network-based solutions DoS-resilient end-point protocol design,Low-Rate Attacks,TCP is vulnerable to low-rate DoS attacks,TCP: a Dual Time-Scale Perspective,Two time-scales fundamentally required RTT time-scal
14、es (10-100 ms) AIMD control RTO time-scales (RTO=SRTT+4*RTTVAR) Avoid congestion collapse Lower-bounding the RTO parameter: AllPax99: minRTO = 1 sec to avoid spurious retransmissions RFC2988 recommends minRTO = 1 sec,The Low-Rate Attack,The Low-Rate Attack,At a random initial time A short burst (RTT
15、) sufficient to create outage Outage event of correlated packet losses that forces TCP to enter RTO mechanism The impact of outage is distributed to all TCP flows,The Low-Rate Attack,The outage synchronizes all TCP flows All flows react simultaneously and identically backoff for minRTO The attacker
16、stops transmitting to elude detection,The Low-Rate Attack,Once the TCP flows try to recover hit them again Exploit protocol determinism,The Low-Rate Attack,And keep repeating RTT-time-scale outages inter-spaced on minRTO periods can deny service to TCP traffic,Low-Rate Attacks,TCP is vulnerable to low-rate DoS attacks,Vulnerability of Receiver-Based TCP to Misbehaviors,Sender-based TCP Control functions given to the sender,Receiver-Based TCP,Receiver decides how
