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

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

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SUMMARY

This document presents a specific case of IP address allocation – allocation in geographically-separated locations within an LTE network. In case of dynamic allocation, no matter where a user accesses, a dynamically selected P-GW dynamically allocates an IP address to the user for PDN connection. In case of static allocation, however, there is always one specific P-GW and one IP address for a user - the designated P-GW allocates a static IP address for the user’s PDN connection. Here we will use an LTE network that serves two cities as an example to describe different ways and procedures of IP address allocation, and see how they are different from each other.

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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

1. Introduction

The previous document, IP Address Allocation Schemes I [1], has covered the basic allocation procedures, explaining how an LTE network allocates IP address to a user when the user attempts to access the network at different times (t=t1 and t=t2) while staying at one place. This document goes a little more specific, studying the allocation procedure where a user is accessing from two geographically-separated service locations (e.g. City 1 and City 2) within an LTE network. As in the previous document, two types of allocation methods (dynamic and static) will be discussed. Additionally, we will learn how a P-GW, the connecting point between UE and Packet Data Network (PDN), is selected, and how a default bearer route is set accordingly.

In case of dynamic allocation, the LTE network allocates a dynamic IP address (PDN address) to UE no matter which city the UE is accessing from, and the UE can connect to a PDN through a P-GW by using the IP address. The IP address allocation procedure is the same as in the previous document regardless the user’s access location. However, in case of static allocation, the network allocates one permanent IP address, allowing UE to connect to a PDN through one designated P-GW, no matter where the UE is accessing from. The procedure is the same as in the previous document in that a permanent IP address is allocated according to the user’s subscription profile. But, it is different in that a default bearer route can be set either within the city the UE accessed from or between two geographically-separated cities, now that there is one designated P-GW (connecting point to PDN).

This document is organized as follows:

In Chapter 2, different types of IP address allocation – dynamic and static - and their characteristics will be discussed.

Chapters 3 and 4 will provide the detailed explanation of the dynamic and static allocations, respectively.

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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