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A Layer-2 Approach for Mobility and A Layer-2 Approach for Mobility and Transport in the Mobile BackhaulTransport in the Mobile Backhaul

Author : Nuutti Varis, Jukka Manner, Johanna Heinonen

Source : International Conference on ITS Telecommunications, 2011

Presenter: Chao-Chin Chang

Date : 2012/03/21

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OutlineOutline

INTRODUCTION MOBILITY MANAGEMENT IN 3GPP R8 BASIC ETHERNET-BASED MOBILITY TRILL TRILL-BASED MOBILITY MANAGEMENT IN

ACCESS NETWORKS MOBILITY MANAGEMENT IN THE MOBILE

BACKHAUL SIMULATIONS

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INTRODUCTION INTRODUCTION

The cell sizes decrease, leading to much more frequent handovers

Implement mobility management functions in the link layer without user specific tunnels as an alternative to the current IP-based solution

TRILL is an attempt to solve some of the problems of the standard STP-based Ethernet

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MOBILITY MANAGEMENT MOBILITY MANAGEMENT IN 3GPP R8IN 3GPP R8 Traffic flow templates in the UE and PDN-GW

map traffic to the right bearer

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MOBILITY MANAGEMENT MOBILITY MANAGEMENT IN 3GPP R8IN 3GPP R8 Downsides of GTP :

The tunnel needs to be re-created after every handover, the signaling load due to the handovers increases when the cell sizes become smaller

GTP works over IP and UDP, thereby it introduces in IPv4 networks an overhead of 36 bytes to every user packet (56 bytes in IPv6)

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BASIC ETHERNET-BASED BASIC ETHERNET-BASED MOBILITY MOBILITY Implement the mobility of the UEs in L2

instead of L3 The GTP based bearer model is

implemented with Ethernet L2 MAC addresses are used as locators and

IP addresses only identify the users The identifier is the UE IP address allocated

for each user by the PDN-GW during the attach procedure.

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BASIC ETHERNET-BASED BASIC ETHERNET-BASED MOBILITY MOBILITY User specific GTP tunnels are not used Ethernet and VLANs in the mobile network

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BASIC ETHERNET-BASED BASIC ETHERNET-BASED MOBILITY MOBILITY Outer VLAN (S-VLAN) is used to separate

traffic destined to different eNB groups Inner VLANs (C-VLANs) are used to

separate different traffic types and QoS classes

3GPP signaling towards the MME element has a C-VLAN of its own

Do not require routing change signaling through the carrier core

No GTP tunnel needs to be re-initialized

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BASIC ETHERNET-BASED BASIC ETHERNET-BASED MOBILITY MOBILITY Employ mapping of addresses on the CE

switches The S-GW sends user data with the

destination MAC address of the CE switch All handovers under the same CE and

access network remain unnoticed by the S-GW

Uses an extended TRILL-based technology in the access network, and the core is based on legacy Carrier Ethernet

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TRILLTRILL

The TRILL protocol is an evolutionary approach to Ethernet bridging Solving forwarding table state explosion by use of

a link-state protocol TRILL also solves the broadcast storm issues

The link-state protocol computes Shortest Path First (SPF) trees in the campus, allowing RBridges to optimally route traffic to every other Rbridge

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TRILLTRILL

Example of TRILL

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TRILLTRILL

The downside of TRILL: introduces new Ethernet headers, thus increasing

the MAC layer overhead on the link TRILL DHT(Distributed Hash Table) location

service Unicast Ethernet frames destined to unknown

end-stations Enable end-station mobility directly on the link

layer Create a distributed ARP service for the whole

TRILL campus

13TRILL-BASED MOBILITY TRILL-BASED MOBILITY MANAGEMENT IN ACCESS MANAGEMENT IN ACCESS NETWORKSNETWORKS Packet transport in the Ethernet-based network

14TRILL-BASED MOBILITY TRILL-BASED MOBILITY MANAGEMENT IN ACCESS MANAGEMENT IN ACCESS NETWORKSNETWORKS Advantages to using an IP based location

service in the access network ARP can be directly utilized as a location update

trigger from eNBs Avoiding the MAC learning table state explosion

effect in the access network

15TRILL-BASED MOBILITY TRILL-BASED MOBILITY MANAGEMENT IN ACCESS MANAGEMENT IN ACCESS NETWORKSNETWORKS The updated location information is sent to

the relaying Rbridge Insert or update the location information in the

local copy of the DHT information database If the RBridge nickname of the location

information changed, signal the new location information back to the old Rbridge

16TRILL-BASED MOBILITY TRILL-BASED MOBILITY MANAGEMENT IN ACCESS MANAGEMENT IN ACCESS NETWORKSNETWORKS Location state repair after mobility event

17MOBILITY MANAGEMENT IN THE MOBILITY MANAGEMENT IN THE

MOBILE BACKHAULMOBILE BACKHAUL The mobile core and access networks must

exchange information as follows : The S-GW must learn the CE MAC addresses After an UE attach procedure, must inform the

access network about the new UE IP address and its location

If the UE performs a handover across access networks, the signaling needs to go through the S-GW and MME

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SIMULATIONSSIMULATIONS

Simulations of the Ethernet-based solution

Handover Rate

Mobility

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SIMULATIONSSIMULATIONS

Ethernet-based packet transport removes the GTP-tunneling, saving tens of bytes for each packet

The solution presented in this paper can hide handovers from core network in a similar way as the RNC does in 3G networks

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CONCLUSIONSCONCLUSIONS

User data packets are routed in L2 and therefore the GTP-U protocol is not used

The signaling load to the mobile core network is decreased

In the user plane the protocol overhead is decreased because of missing IP/UDP/GTP layers