IEG 4180 Tutorial 11

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IEG 4180 Tutorial 11

• Prepared by Zero

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Message Flow

• Simplex
• Uni-directional communication
• The sender / receiver role is fixed
• Duplex
• Bi-directional communication
• Both party can pick the two roles
• Half- Duplex
• At each time, messages can flow in only one
  direction
• Full-Duplex
• Messages can flow in only any direction at any
  time

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Protocol Design

• Type
• Control information
• Protocol header, flags identifying message
  purpose
• Data
• Resource to be requested or responded
• Headers are composed of
• Fixed header fields (must have, e.g. regarding to
  which session)
• Variable/optional header fields (optional, e.g.
  extra information like timestamp)

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Protocol Design (cont.)

• Message boundary and fields boundary
• Fixed length or use delimiter (implicit /
  explicit)
• Text (mostly require variable length)
• Use human readable text for communication
• Binary (mostly require fixed length)
• Use binary for communication

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Protocol Design (example)

• Regarding to Streaming Server (SS) uploading the
  list of files to Directory Server (DS)
• Text example
• Send out
• DS keep receiving until it find \0\0
• Binary example
• Send out
• DS receive the first 5 bytes through MSG_PEEK
  flagAccording to id, it uses normal receive up
  to the specified size (int type)DS will further
  extract the file names according to the length
  specified by l

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NAT

• Allowing internal hosts communicate with external
  hosts as if they are in the same network
• Translating internal and external address
  according to certain table entry (if exist)
• Table entries are created
• Automatically connection is initialized by
  internal host
• Manually specify directing all traffic for
  certain port to port of another specified
  internal host

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NAT (Type)
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Traffic Elasticity

• Elastic
• Can tolerant degradation of resource quality
• Inelastic
• Require certain level of resource quality
• Metrics in describing resource quality
• Delay
• Bandwidth
• Data integrity
• Burstiness