5 Traffic Flow in the LTE Network
5.1 Traffic flow in uplink direction
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Traffic flow from UE to Internet
  1.  A UE transfers user IP packets to an eNB over LTE-Uu interface.
  2. The eNB encapsulates the user IP packets with the S1 GTP tunnel header and forwards the resulting outer IP packets to the S-GW. Here, the eNB selected a “TEID” value (i.e. UL S1-TEID), “Destination IP Address” (i.e. S-GW IP address), and “Source IP Address” (i.e. eNB IP address) to make the S1 GTP tunnel header.
  3. After receiving the outer IP packets, the S-GW strips off the S1 GTP tunnel header, encapsulates the user IP packets (the inner IP packets) with the S5 GTP tunnel header and forwards the resulting outer IP packets to the P-GW. Here the S-GW selected a “TEID” value (i.e. UL S5-TEID), “Destination IP Address” (i.e. P-GW IP address), and “Source IP Address” (i.e. S-GW IP address) to make the S5 GTP tunnel header.
  4. After receiving the outer IP packets, the P-GW gets the user IP packets by stripping off the S5 GTP tunnel header and transfers them to the Internet through IP routing.