Introduction

• provide logical communication between application processes running on different hosts
• transport protocols run in end systems
• transport layer relies on, enhances network layer services

	transport layer	network layer
data transfer	between processes	between end systems

transport-layer protocols

Internet transport services

• TCP

  reliable, in order unicast delivery

  • congestion control
  • flow control
  • connection setup
• UDP

  unreliable("best-effort"), unordered unicast or multicast delivery

• services not available
  • real-time
  • bandwidth guarantees
  • reliable multicast