Implementing A Very Simple Protocol

Very Simple Virtual Circuit Protocol

Goals

• Describe basic user procedure
• Begin to describe underlying architecture and components
• Talk about substrate concept

Versions

• 0
  • VCI in first word of UDP payload
  • VCI is globally unique
• 1
  • VCI can change during transit as part of pkt processing

User-space pkt

• Tunnel socket appears in UDP header
• VCI is first word of UDP payload
• Payload also has timestamp (for RTT and space-time diagram)

User-Space Implementation

• Filters for local delivery
• User-space process
  • Has VCI-MI Socket map; i.e., M : VCI --> MI Socket
  • Forwards pkt to socket M(pkt.VCI)

Fastpath Implementation

• Requires mods to Parse and Header Format
• Uses generic Lookup

Interesting Example