Section: 9.3.2 EPS bearer identity
Content: Bits 5 to 8 of the first octet of every EPS Session Management (ESM) message contain the EPS bearer identity. The EPS bearer identity and its use to identify a message flow are defined in 3GPP TS 24.007[ Mobile radio interface signalling layer 3; General Aspects ]  [12]. If the UE or the MME or both do not support signalling for a maximum number of 15 EPS bearer contexts, the MME shall select the EPS bearer identity from the value range 5 to 15, or select the value 0 when it needs to indicate that no EPS bearer identity is assigned. NOTE: When assigning EPS bearer identities from the range 1 to 4, the MME can take into account that these EPS bearer contexts will be subject to local deactivation if the UE performs inter-system change to A/Gb mode or Iu mode or if it performs a change to an MME not supporting signalling for a maximum number of 15 EPS bearer contexts.