Xpress Transport Protocol

1
Xpress Transport Protocol
XTP

• 2000. 3. 22.
• ???
• 985223
• ????

2
References

• W. Timothy Strayer, etc., XTP The Xpress
  Transfer Protocol, Addison-Wesley, 1992
• Rajkumar Buyya, High Performance Cluster
  Computing,. Vol. 1, Prentice Hall, 1999

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Introduction

• Cluster computing
• low-latency communication
• duplicate data
• TCP no multicast, reliable
• UDP mulitcast, unreliable
• XTP
• reliable/unreliable transport multicast
• multicast group management
• fast connection setup / teardown
• transaction
• high-throughput / low-latency

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Network Services for Cluster

• peer-to-peer duplicate data ???
• multicast group management
• priority latency control
• fully reliable - ??? unreliable
• single message 6 packets
• error go-back-n vs. selective retransmission
• fixed policies by the protocol
• by application
• XTP mechanisms, user policy

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XTP

• not replacement for TCP or UDP
• TCP, UDP over IP
• XTP
• IP
• CLNP
• LLC or MAC
• ATM

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Multicast

• multicast
• unicast
• broadcast
• multicast
• security
• monitor / enforce group membership

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Group management

• Multicast Group Management
• membership by group manager
• selectively allow/deny
• failure of a member
• delete the member and continue
• abandon transmission entirely
• other action
• example
• 3 member reliable, the others unreliable

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Priority

• Most important data first
• Priority bit, priority value
• Lower the value, higher the importance
• Router must support XTP

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Rate / Burst Control

• Error occurrence (on fiber optic network)
• bit error ?
• buffer overrun in the receiver
• congestion in the routers
• TCP flow control, end-to-end
• XTP rate/burst control, path
• rate control amount of data / unit time
• burst size of data
• Router

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Connection Management

• TCP, TP4 6 packets / one data
• XTP 3 packets / one data
• (1) open connection, data, request for closure
• (2) acknowledgement
• (3) acknowledgement of connection closure

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Selectable Error Control

• WAN vs. LAN
• WAN missing, delay
• LAN missing, no delay
• XTP Error control
• fully reliable mode
• no error mode no ACK, digitized voice
• fast negative ACK
• receiver out-of-seq data -gt missing packet
• LAN
• error control options on a single protocol

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Selectable Flow Conrol

• Flow control options
• Traditional flow control
• sliding window
• Reservation mode
• receivers buffer credit
• no lost due to buffer starvation
• Free flow, no flow mode useful for
  intracluster multimedia application

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Selective Retransmission

• Old TCP go-back-n
• bad Application
• high capacity
• long delivery latencies
• XTP selection
• go-back-n
• selective retransmission span

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Selective Ack

• XTPs ACK
• if and when decided by the user
• always / sometimes / never
• transmitters request the status of the
  connection
• transmitter SREQ bit set
• -gt receivers CNTL packet

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MTU Detection

• Maximum Transmission Unit
• OSIs fragmentation
• transport layer
• network layer
• MTU negotiation
• Minimum of MTUs on the path

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Out-of-band Data

• information about the data stream without
  embedding it within the data stream itself.
• tagged data 8 bytes
• existance of the tagged data
• semantic information about the data
• (eg) cluster computing of real-time data
• timestamp

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Performance

• XTP vs. TCP/UDP/TP4
• unicast comparable to TCP
• Reliable multicast
• XTP gt TCP, UDP
• TCP unicast N
• UDP unreliable multicast

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Throughput

• small messages similar
• larger messages
• UDP unreliable unicast gt XTPs reliable unicast
  gt XTP reliable multicast gt TCP reliable unicast

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Message Throughput

• how fast it can transmit messages of varying size
• real-time control application
• large messages similar
• small messages 2 over TCP, UDP
• XTP reliable unicastgt XTP reliable multicastgt
  XTP unreliable unicast gt TCP, UDP

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End-to-end Latency

• user-memory-to-user-memeory one-way latency
• 16 byte 228 microseconds128 byte 2411024
  byte 3364096 byte 65716 Kbyte 1656

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Applications (1/2)

• Multicast
• Gigabyte files
• selective retransmission
• High performance weapons control
• low end-to-end latency
• Very high resolution image
• high throughput multicast
• Digital Telephone
• multicast

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Applications (2/2)

• Video File Server Video mail
• multimedia
• Priority Support
• digital multimedia
• XTP-aware IP router
• XTP priority

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Future

• XTP Functionality
• transport layer multicast
• multicast group management
• selective retransmission
• transport layer priority
• Not Performance but Functionality
• Public Sandia National Labs SandiaXTP
• Commercial Version

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Comparison (1/2)

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Comparison (2/2)