E flag and Label fields

• E=0 means Label filed is 28 bits long and contains a single label. E=1 means Label filed is 60 bits long and contains two labels

  • The first 28 bits are a lower level label
  • The next 32 bits are a higher level label
  • This provides support for pushing and popping labels on a label stack

• Label format and semantics depend on a port's PortType attribute

• ATM label (never stacked):

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