Good Solutions to Support Highly Tolerant Services... Programmatic - - PDF document

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May 02, 2023 105 likes •219 views

H YDRA N ET-FT: Network Support for Dependable Services Gurudatt Shenoy Suresh K. Satapati Riccardo Bettati Department of Computer Science Texas A&M University Failure Scenarios Failures aint what they used to be. disaster type

SLIDE 1

HYDRANET-FT:

Network Support for Dependable Services

Gurudatt Shenoy Suresh K. Satapati Riccardo Bettati Department of Computer Science Texas A&M University

Failure Scenarios

system site service

disaster type “crash”

host network server network local distributed

verload

DOS attack

“Failures ain’t what they used to be.”

SLIDE 2

Good Solutions to Support Highly Tolerant Services...

Programmatic Requirements … provide service replication across geographically distributed server hosts. … can be deployed and recalled on demand. … preserve server control over data. … support any service. … can be incrementally deployed. … remain fully transparent to clients. both mechanisms and recovery! Tolerance Requirements … support atomic multicast. … ensure message ordering. … provide low-latency failure detection mechanisms.

The HYDRANET Approach to Redirection/Replication

server host clients service host server redirector

Bring services near to clients.
Operate replicas under server’s control and identity.

service service replica

SLIDE 3

Mechanisms for Redirection

host server “get from A” “telnet to A” redirector

http telnet

80 25

http

rigin

host “get from A”

mail

25 Origin IP Redirect IP Port 128.194.132.34 128.101.133.12 128.101.134.1 80 128.101.134.1 25 128.101.134.1 128.194.132.34

Performance Gains through HYDRAWEB Replication

gin 2 tiramisu (direct) (98/05/29 11:50am ) 1 10 100 1000

1 501 1001 1501 2001 2501 latency (msec) frequency

gin 2 tiramisu (half cache) (98/05/28 4:20pm)

1 10 100 1000 1 501 1001 1501 2001 2501 latency (msec) frequency

No Replication HYDRAWEB Replication

Access latencies for 1kB HTTP objects.

Origin host: berkeley.edu Client host: tamu.edu Origin host: berkeley.edu Client host: tamu.edu Host server: tamu.edu

SLIDE 4

The HYDRANET-FT Approach to Support of Highly-Tolerant Services The HYDRANET-FT Approach to Support of Highly-Tolerant Services

SLIDE 5

The HYDRANET-FT Approach to Support of Highly-Tolerant Services HYDRANET-FT: Supporting Tolerant Services through Fault-Tolerant TCP

Synchronization paradigm
Atomicity
Message ordering
Low-latency error detection
Virtual synchrony

SLIDE 6

HYDRANET-FT: Mechanisms

client

TCP machinery host socket buffer replicated application

HYDRANET-FT: Mechanisms

client Synchronization at Socket Buffer Layer

SLIDE 7

HYDRANET-FT: Mechanisms

client Atomicity through Acknowledgement Channel

ACK-stream data-stream

HYDRANET-FT: Mechanisms

client Atomicity through Acknowledgement Channel

ACK-stream data-stream tcp core tcp core tcp core

ACK-channel

SLIDE 8

HYDRANET-FT: Mechanisms

client Message Ordering:

Source ordering enforced by TCP.
Total ordering across connections enforced by ordered delivery on

acknowledgement channel.

tcp core tcp core tcp core

HYDRANET-FT: Mechanisms

client Failure detection provided by TCP re-transmission at client.

tcp core tcp core tcp core

!

SLIDE 9

Implementation

FreeBSD 3.1
Modifications

– Process control – IP forwarding – TCP machinery

Additional control system calls

int v_host(u_long ip_address); int setportopt(port, mode, detector_parameters)

Performance Measurements

Comparison of Various Schemes

100 200 300 400 500 600 16 32 64 128 256 512 1024 Packet Size (* 1000 Byte) Throughput (KBps)

FT-old Scheme 1 Scheme 2 Scheme 3 Scheme 4 Clean Primary Only Redirection (no FT)

SLIDE 10

Demonstration: Real time Video Streaming

File Type: Mpeg (5 MB) Frame Rate: 30.2 fps # Frames: 1509 Player: mTv (for FreeBSD) Client Host: Dell Inspiron (PII) Server Host(s): Intel PI 120 MHz Router: Intel 486/DX Network: 10 MBps Ethernet Infrastructure: HydraNet-FT Movie Servers ACKChannel

Topology

Client (Movie Player) Redirector

FT-TCP FT-TCP

Conclusion

Summary

– Starting point: Traditional support for tolerance allocated either too high or too low in protocol stacks to allow for easy deployment on a large scale. – HYDRANET-FT – Satisfy declared requirements – Very-low latency recovery (client invisible) – Transparent on server side.

Outlook

– Integrated control interface for server management – Demonstration of behavior for time-critical applications (video streaming) – Support for server camouflaging (hiding servers by geographically spreading profile)