Table of Contents
We have learned about the LTE ID groups such as UE and ME IDs, and Network Equipment (NE) and UE location identifier (location) IDs in LTE Identification 1  and LTE Identification II , respectively.
This document, as the third document of the LTE Identification series, describes EPS Session/Bearer IDs related to user traffic delivery. E2E sessions that include application entities are out of the scope of this document, and hence only EPS sessions that provide users with PDN connectivity will be covered herein. In Table 1, EPS Session/Bearer IDs to be discussed herein are shown in the last row with a gray background.
Table 1. Classification of LTE Identification 
The LTE IDs that we have learned in  and  are used to identify a different UE, ME and NE in an LTE network, whereas EPS Session/Bearer IDs are used in a UE1. This means, since more than one EPS session and bearer can be established in a UE concurrently, IDs are needed to identify them.
Hi, Netmanias Team.
Thanks for your good response.
About "more than one session can use the same EPS bearer. ":
One session means one PDN connection. Is it right?
If so, different session may not use same EPS bearers as each EPS bearers can only have one LBI. In other words, each beaer is linked to only one PDN. Maybe I am wrong if one session does not mean one PDN connection.
1. Thanks for the good work from Netmanias team.
2. I do have the same doubt about this. Different PDN connections will setup different default EPS bearers, how can an EPS session use the same EPS bearer if one EPS session means one PDN connection?
I think there is a tiny mistake in this excellent paper:
An APN is a combination of a network ID and an operator ID. The network ID is used when identifying PDNs such as Internet or cooperate VPNs or identifying services like IMS that the PDN provides.
An APN is a combination of a network ID and an operator ID. The network ID is used when identifying PDNs such as Internet or Corporate VPNs or identifying services like IMS that the PDN provides.
Thank you for your kind comment. The typo has been corrected (as Corporate VPNs) on the post and the attached file.
Do you have any plan for VoLTE Technical Documents? Thank you.
Thanks for the good paper.
I have one stupid question: what's the difference between the EPS sessions and IP flows?
I'd expect you can find answer in link below:
http://www.netmanias.com/en/?m=view&id=techdocs&no=5908 (LTE QoS: SDF and EPS Bearer QoS)
In my understanding,
- EPS session = PDN connection
- An EPS session can have single or multiple EPS bearers
- EPS bearer is transmission path between UE and P-GW to deliver user traffic (IP flows) with specficied QoS
- An EPS bearer can have single or multiple IP flows
Thanks for your explanation. I'll check the paper you recommended.
can we think of gtp load balancing between eNB and S-GW.
I really need it.
I love your answers, especially this one:"whether eNB knows EPS bearer ID". Thank you!
Why do have concept of ERABID and EPS Bearerid when there is 1 to 1 mapping b/w two and also there value is always same. We could have used any one of the IDs.
Refer to the TS 23.401 as shown below:
5.2.1 EPS bearer identity
An EPS bearer identity uniquely identifies an EPS bearer for one UE accessing via E-UTRAN. The EPS Bearer Identity is allocated by the MME. There is a one to one mapping between EPS RB and EPS Bearer, and the mapping between EPS RB Identity and EPS Bearer Identity is made by E-UTRAN. The E-RAB ID value used at S1 and X2 interfaces to identify an E-RAB is the same as the EPS Bearer ID value used to identify the associated EPS Bearer.
The description is perfect and well structured, as always.
Keep up the good work!
If say GTPU and PDCP on eNB are not on same system (dis-integrated stack), for DL traffic after GTPU decapsulation when UE IP clear packet is submitted for PDCP prorcessing, what is the best way to identify DRB in PDCP leayer? Can we assume UE IP address and ToS value in IP header is unique for every DRB?
In Figure 4. Bearer IDs allocators, I think P-GW should be responsible for S5 TEID DL allocation, not UL. S5 TEID UL allocation is done by S-GW which is already indicated there.
What happens to the dedicated bearers when the linked default bearer is deactivated ? If the dedicated bearer will also gets deactivated, then how will it be done ? how will dedicated bearer comes to know that default has been deactivated ? What action does it take ? Whats the procedure ?
Hi， there is one thing confuse me that what is the relationship between the Eps and SRB(singling ridio bearer)。 thank you