CATNIP

1
CATNIP Context Aware Transport/Network
Internet Protocol
Carey Williamson Qian Wu Department of
Computer Science University of Calgary
2
Why CATNIP

• Layered protocol stacks

3
Why CATNIP (Contd)

• Observations in Web data transfer using TCP/IP
• Poor protocol interactions
• TCPs window-based flow control mechanism
  produces data bursts
• Not all packet losses are created equal. Packet
  losses are costly for small document transfer
• A TCP source has limited control over packet loss
  effects
• An IP router has significant control over packet
  loss effects.

4
(No Transcript)
5
Design of CATNIP

• Can we make the TCP/IP protocols smarter about
  the specific job?
• Convey application-layer context information to
  the TCP and IP layers

Application
Transport
Network
6
Design of CATNIP (Contd)

• Adding context-awareness to TCP
• Rate-Based Pacing of the Last Window (RBPLW)
• Early Congestion Avoidance (ECA)
• Selective Packet Marking (SPM)
• Use the reserved high-order bit in the TCP
  header to convey packet priority information

7
(No Transcript)
8
Design of CATNIP (Contd)

• Adding context-awareness to IP
• CATNIP-Good

• CATNIP-Bad
• CATNIP-RED RED CATNIP-Good

9
Evaluation of CATNIP
Simulation ns-2
Evaluation
Emulation use WAN emulation to test a prototype
implementation of CATNIP in the Linux kernel of
an Apache Web server.
10

• Evaluation using simulation
• Network model

Client 1
Server 1
10 Mbps, 5 ms
10 Mbps, 5 ms
Client 2
1.5 Mbps, 5 ms
Server 2
RouterS
RouterC
Client 99
10 Mbps, 5 ms
10 Mbps, 5 ms
Client 100
Server 10
11

• Evaluation using simulation (Contd)
• Web workload model
• 10 Web pages
• Use empirically-observed distribution to
  determine the size, and the number of embedded
  images

12

• Evaluation using simulation (Contd)
• Factors and Levels

• Performance metrics
• the transfer time for each Web page
• the average packet loss

13

• Simulation results
• DropTail routers
• Mean and standard deviation of transfer times

14

• Packet loss

• Observations
• TCP endpoint control algorithms have little
  advantage to offer.

15

• Simulation results (Contd)
• CATNIP-Good routers
• Mean and standard deviation of transfer times

16

• Packet loss

• Observations
• Adding context-awareness at the IP routers
  improves the mean Web page transfer times and the
  standard deviation of the transfer times.
• The average packet loss rates with CATNIP-Good
  are higher than for the DropTail routers.

17

• Simulation results (Contd)
• CATNIP-Bad routers
• Mean and standard deviation of transfer times

18

• Packet loss

• Observations
• Packet losses are shifted to the high priority
  TCP packets, that is, throw away the wrong
  packet at the wrong time, therefor makes
  matters worse.

19

• Simulation results (Contd)
• CATNIP-RED routers
• Mean and standard deviation of transfer times

20

• Observations
• Reno and ECA perform similarly in almost all
  cases.
• The effect of CATNIP-RED is greater than the
  effect of ECA.

21

• Experimental Implementation and Evaluation
• Experimental environment
• WAN emulator IP-TNE (Internet Protocol Traffic
  and Network Emulator)
• Web server
• Apache Web server (version 1.3.19-5) runs on top
  of modified Linux 2.4.16 kernel.
• Implementation focused on the SPM feature only

22

• Network model

Client 1
10 Mbps, 5 ms
Client 2
10 Mbps, 5 ms
1.5 Mbps, 5 ms
RouterS
RouterC
Endpoint
Server
Client 99
10 Mbps, 5 ms
Client 100
WAN Emulation

• Primary Factor
• buffer size of the bottleneck link (64 KB --
  512 KB)

23

• Evaluation results

24

• Conclusions
• Not all packet losses are created equal
• A TCP source alone has limited control over Web
  data transfer performance, even with
  application-layer information
• The IP layer has a significant influence on Web
  data transfer performance, particularly when
  application-layer context information is
  available
• A simple change to the TCP/IP stack
  implementation can provide the context
  information
• Changes to the queue management at routers can
  provide significant performance advantages for
  the context-aware TCP/IP.

25
Questions?