LTE IP Address Allocation Schemes II: A Case for Two Cities

February 17, 2015 | By Netmanias (tech@netmanias.com)

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Table of Contents

1. Introduction
2. Types of IP Address Allocation

3. Dynamic IP Address Allocaion

4. Static IP Address Allocation

5. Closing

2. Types of IP Address Allocation

Below, we will describe the allocation procedure using a two-city model in one of our EMM scenarios presented previously [2]. In this scenario, we assume there are MME, S-GW and P-GW in each city (City 1 and City 2). Each P-GW has its own IP pool(s), and only City 1 has HSS. UE uses only one PDN service (Internet). When requesting for a PDN connection, UE requests for DNS server IP addresses as well as a PDN address (IPv4 address). The scenario details are as follows:

①	In City 1, a user turns on UE, accesses the LTE network, and uses a PDN (Internet) service.
②	After using the Internet service, the user turns off UE, and moves to City 2.
③	Upon arriving at City 2, the user turns on UE again, accesses the LTE network, and uses a PDN (Internet) service.

During initial attach in City 1 or City 2, UE requests MME for PDN connection¹. Upon the request, the MME selects a P-GW through which the UE can access the PDN, and the P-GW determines an IP address (i.e. PDN address) for the UE to use a PDN service. The P-GW forwards the IP address to the UE while a default bearer is being established, so that the UE can use the PDN service with the IP address.

In this two-city model, IP addresses are allocated in two ways as seen in the previous document – dynamic and static IP allocation. Dynamic IP allocation will be explained in Chapter III and static IP allocation will be described in Chapter IV. IP address allocators and P-GW selection methods in each way are listed in Table 1.

Table 1. IP Address Allocation Methods

Dynamic IP Address

Static IP Address

IP Address Allocator

P-GW
(One from local IP pool is allocated)

HSS
(The one provisioned at HSS is allocated)

P-GW

Selection

MME
(A P-GW is dynamically selected

according to P-GW selection policies)

HSS
(The one provisioned at HSS is selected)

Page 2 of 5

bikramaditya 2015-02-18 15:46:07

How can i download the PDF files for offline review.

Netmanias 2015-02-24 13:13:45

You can download it by pressing the "PDF" icon or "Paper version" text on the top right.

carlos.inatel@gmail.com 2015-05-29 05:44:54

Are there a document to describe IP Provisioning at P-GW with IPV4 and IPV6?

Paulos Rizos 2016-10-05 19:26:09

Dear NetManias, please post more technical documents. Your last post was over a year ago. These quality documents is what attracted so many users to your site in the first place.

tianming 2016-10-20 16:05:46

Hello, i see the 25th document, if have some other document update? as like layer2 or physical layer, thanks.

Prabhat Patel 2017-02-20 14:45:42

Hi, I have a query regarding the IP address allocation to UE.

Suppose we dont have any APN ( default) configuredc on UE and for the same user/IMSI we dont have any subscribers details available to HSS.

Now as the user turn ON the device there will be some signalling message which will flow towards eNB/MME NAS and S1AP messages.

Since as we dont have any APN info available the Attach will fail and no IP will get allocated to the UE.

My doubt is which address will be used by the MME and eNB for the UE to send and receive the control/signaling messages between UE and eNB and UE and MME.

As the address which is allocated for the UE by the P-GW is for the PDN traffic, but here the attach has failed but still some signalling messages is flowing.

So, which UE- ID will the network will use for the UE to send messages to it and who will assign it.

Are these ID's same as eNB-UE S1APand MME-UE S1AP ID's and will these ID's mapped to some set of IP's????

suryadevi 2017-03-17 19:35:49

Hi,

I have the following two questions..

1)Why static IP allocation is required in LTE ?

2)What happens if the SGW is not able to connected to the HSS provided PGW in static IP?

Rina Mhatre 2018-02-13 20:06:45

Thanks for the elaborative description. Here we are taking an example for two different IP pools used per PGW site, what happens in PGW failure situation. Imagine a situation where PGW 1 and 2 are mated pair of each other then how to make sure that IP pool is not idle and reusable by otehr site PGW when any of the PGW is down.

nirav kapoor 2019-04-09 18:49:24

Dear Netmanias Team,

Regarding the provisioning of HSS subscription profile for Statis UE IP and PDN GW id, is it as per 3GPP specifications,

if so, please confirm the clause from the same.

Thanks and Regards,

Nirav Kapoor

hartyagi 2019-12-26 01:37:29

Dear Netmaninas,

I am unable to register or signup with your home page. During signup i am getting error that is required required business mail id.

I dont have any business id and i am a study right now. Please help me to register myself on your account to download some documents from your page.

Please help me on urgent basis, I have put my gmail id and getting the error to register my self on the page.

Rgrds