1
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
2
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
3
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
4
MOBILITY MANAGEMENT MOBILITY MANAGEMENT IN 3GPP R8IN 3GPP R8 Traffic flow templates in the UE and PDN-GW
map traffic to the right bearer
5
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)
6
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.
7
BASIC ETHERNET-BASED BASIC ETHERNET-BASED MOBILITY MOBILITY User specific GTP tunnels are not used Ethernet and VLANs in the mobile network
8
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
9
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
10
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
11
TRILLTRILL
Example of TRILL
12
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
18
SIMULATIONSSIMULATIONS
Simulations of the Ethernet-based solution
Handover Rate
Mobility
19
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
20
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