Transcript AGW - 3GPP2

3GPP2 Network Architecture Evolution
Note - architecture diagram on slide 9 was updated to show the RRM on the
bearer path as agreed last month (March 2006 PSN meeting in Dallas)
Parviz Yegani
Cisco Systems
[email protected]
3GPP2 TSG-X PSN WG
Kansas City, April 24, 2006
Session Number
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Outline
 3GPP2 network architecture evolution guidelines
 3GPP2 All-IP network operation (logical view)
 Mobility model
 Macro vs Micro mobility
 Mobile IP enhancements
 Fast handoff
 Anchored authenticator/Bearer data plane
 Security model for context transfer
 FA Relocation
 PPP Free Operation
 E2E QoS Design Goals
 E2E QoS Signaling using RSVP – an example
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Problems with Current Packet Data Network
The current packet network involves many levels of mobility
including Intra-BSC, Inter-BSC/PCF and Inter-PDSN.
These many levels of mobility are not required and lead to
additional network complexity without bringing additional value.
Additional levels of mobility result in many network elements,
and functionality being split across them, and this can result in
further delays in the network as well as a deterrent to future IP
services.
In addition, there is very close coupling between the Handoff
/Radio Management Control functions and Session Mobility. This
leads to an architecture where the data bearer gets coupled with
handoff and radio management – thereby causing a bottleneck
for scale, or requiring careful engineering of the data transport
network.
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Architecture Evolution …
3GPP2 network architecture should evolve to allow the following
capabilities:
 Cost effective data access
 Flexible, scalable and physical topology independent
 A data-centric architecture based on the internet design concept
 Support of IP infrastructure with any desired backhaul technology
 Open interfaces and interoperability
 AAA based access control and mobility
 Dynamic HA
 minimum latency
 Mobile IP tunneling and L3 mobility
 minimum packet loss
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Architecture Evolution …
(continued)
 Separation of bearer and control
 Support for wireless access security
 Support evolving radio access technologies (HRPD, …)
 Interoperate with other wireless and wireline networks
 Support new features
 PPP Free Operation
 End-to-end QoS
 Improved performance
 Lower latency (Fast Handoff)
 Full IP QoS capability
 Macro/micro-mobility support
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Architecture Evolution
 IP Core
 IP-based signaling, data delivery and networking (SIP, RSVP, DHCP,
DNS, Mobile IP, IPSec)
 Layered design using IETF protocols (layer 3 and above)
 End-to-end IP connectivity (IP QoS support over-the-air, RAN, Core)
 Allow the IP protocol suite to enable lower layer capabilities and
control their resources
 Allow native IP host stacks as in wired networks
 IP RAN
 Extend IP functionality into the RAN by taking IP to the edge of the
radio access network (i.e., cell site)
 Open RAN architecture
 Native IP support within the RAN
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Architectural Assumptions
Base-Stations terminate the MAC/PHY layers.
Session Mobility from the Base-Stations is handled by an IP
protocol, between the Base-Stations and the Access Gateway.
Radio Resource Management is handled as a decoupled
mechanism between the Base-Station and a Radio Management
Server.
The architecture needs to accommodate different termination
points of RLP – entirely at the BS as well as partial termination at
the AGW.
Handoff Control and Radio Resource Management is decoupled
from session management .
The architecture supports mobile stations having a Mobile IP
stack, as well as not having a client Mobile IP stack.
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3GPP2 All-IP Network Operation
Core
Network
RRM
Soft Switch
PSTN
V
AGW/
LMA
IP Core
INTERNET
RRM
V
HA
AGW/
LMA
DHCP, AAA, DNS
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Evolved Network Architecture
m
Macromobility Tunnel
Micromobility Tunnel
Signaling Interface
IP Core
HA
AGW/LMA
AAA/
DHCP
IP RAN
(Localized Mobility)
RRM
BS
MS
BS
BS
Local Mobility
(in the same Radio Domain)
MS
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Mobility Model
CDMA2000 Radio Access Network should evolve toward a target
native IP RAN architecture that consists of the following logical
network entities:
 Home Agent (HA) – an IP node to allow
 Mobile IP anchor point within the Core
 Macro-mobility support across neighboring AGWs
 Access Gateway (AGW) – an IP node to allow
 IP routing capability within each cluster of cells (BSs)
 Micro-mobility support across cells within a radio domain to
reduce handoff latency, signaling traffic, etc
 Local Mobility Anchor (LMA) – an extension of the AGW function to
support
 Fast handoff across neighboring AGWs
 Base Station (BS) - a layer 2 entity that supports only
 Radio MAC/PHY functions
 IP tunneling termination point (no IP routing support)
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Mobile IP Basic Handoff Operation
Reg. Request
Reg. Reply
HA
Tunnel
Visited Network
old
AGW
new
AGW
FA advertisement
HA
Tunnel
Visited Network
old
AGW
new
AGW
MN
Before Handoff
Tunnel
old
AGW
Visited Network
new
AGW
packets lost
MN
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HA
During Handoff
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MN
After Handoff
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Macro-mobility (Basic Mobile IP)
Mobile IP currently used in the 3GPP2 network
for macro-mobility
Allows seamless mobility over heterogeneous
access technologies
Basic Mobile IP introduces increased network
overhead when MN moves far away from HA
This overhead might not be acceptable for
some applications
Enhancements are needed to minimize delay
and packet loss
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Mobile IP Fast Handoff Operation
Reg. Request
Reg. Reply
HA
HA
Tunnel
HA
Tunnel
Visited Network
Tunnel
Visited Network
AGW(LMA)
AGW(LMA
)
Tunnel
Visited Network
AGW(LMA)
Tunnel
old
AGW
MN
new
AGW
FA advertisement
old
AGW
packets lost
Before Handoff
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Tunnel
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new
AGW
MN
During Handoff
old
AGW
new
AGW
MN
After Handoff
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Micro-mobility (Fast Handoff)
 Mobile IP can be optimized by allowing localized IP
mobility via Fast Handoff
 Fast handoff handles local movement using Local
Mobility Anchor (LMA)
 A new FA in a local domain (zone) can interact with LMA
without engaging the HA
 This improves network performance by reducing delay
and packet loss
 It can also eliminate mobility signaling traffic between
MN and distant HAs during handoff and intra-domain
location updates
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Context Transfer for Fast Handoff
AAA
Initial Keys
HA
Avoid High
Latency
Activity
optimized data path
Authenticator
anchored here
Radio Bearer Cloud
Anchor
AGW
LMA
Keys
AGW-1
AGW-2
AGW-3
AGW-4
FA
FA
FA
FA
Cell Bearer Clouds
BS
1
BS
2
MS
MS
Movement
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BS
BS
3
MS
Context
Movement
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4
MS
Key
Distribution
and usage
BS
MS
MS
Optimized
Data flow
over MIP tunnel
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Security Model for Context Transfer
 Session is anchored at the first GW through which the MS
connects to the network
 HA and Anchor GW have trust relationship with Home AAA
 Anchor GW and HA are in different administrative domains
 Trust relationship needs to be set up before signalling
 Home AAA distributes keys to Authenticator/Anchor GW and HA
 HA has to authorize setup of forwarding path for MS to Anchor GW
 Signaling between HA and Anchor GW needs to be secure
 Anchor GW relocation may take place if the mobile moves far
enough from the current anchor point to optimize data path
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AGW Relocation
a) User is connected to
AGW1, and moves to BS3
connected to AGW2.
b) User registration at BS3
indicates that user is
currently served by AGW1.
AGW2 contacts AGW1.
c) AGW1 sends an indication
to AGW2 to relocate user’s
FA. The user context
(accounting, diameter etc.)
is transferred to AGW2.
d) For Client MIP option,
AGW2 sends out FA
advertisement to user, else
the AGW2 sends out a
trigger to the Proxy MIP
entity.
e) MIP registration to Home
agent is completed now in
both scenarios.
mm
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Anchor of Data Bearer
a) In certain scenarios, it may be
necessary to anchor data
bearer at current AGW during
inter-AGW handoffs.
b) Such bearer anchoring would
not change the location of the
FA. The data bearer is handled
by the Anchor.
c) Traffic from Anchor AGW can
be routed directly to Target BSs
in fully meshed topology.
d) Movement across
administrative or other
boundaries require traffic from
Anchor AGW to respective BSs
to be forwarded via the target
AGW.
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Initial Registration
m
AAA
HA
(5)
(6)
(9,10)
AGW
(2)
(3)
(4)
(10) (7)
(8, DHCP)
BS
(1), (4)
(11)
1.
MS connects to BS
2.
IP BS starts registration to AGW.
3.
AGW confirms user registration (all user traffic +
authentication is now sent to AGW)
4.
AGW starts Access Authentication (EAP) with the MS
5.
AGW contacts AAA server for EAP authentication
6.
AAA Server authenticates user, and returns user
specific parameters – Master Key, HA IP address, other
policies
7.
Access Authentication completes – MS receives
encryption keys
Context State is created
8.
MS starts DHCP exchange to get host configuration
9.
AGW registration towards HA (CoA = AGW) and
forwards PMIP security info to AGW
10. HA creates binding entry for the user and returns user
IP address, and associated host configuration
11. BS returns assigned host configuration to user using
DHCP
Context State Updated
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Inter-BS HO
-
HA
1.
MS informs BS1 of intention to
move to BS2
2.
BS1 sends HO notification over to
AGW (with target BS ID = BS 2, User
Info)
3.
AGW forwards HO notification to
BS2, with context transfer to BS2
(This allows BS2 to construct all
user information)
4.
BS2 responds to AGW that it is
ready to receive new user – sets up
parallel tunnel to handle user
(*depending on latency
requirements this can move later*)
5.
AGW responds back to BS1 to
confirm user moved to target = BS2
6.
BS1 responds back to user, asking
to move to BS2
7.
User moves to BS2
8.
BS2 sends binding update to AGW
9.
AGW sends binding update to HA (if
required)
(9)
AGW
AAA
(2)
(5)
(8)
(3)
(4)
BS1
(1)
(6)
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(7)
BS2
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AGW Transfer
mm AAA
AGW1
AGW2
1.
MS informs BS1 of intention to move to BS2
2.
BS1 sends HO notification over to AGW (with target BS ID =
BS 2, User Info). AGW identifies corresponding target AGW
connected to BS2
3.
AGW1 forwards HO notification to AGW2 with associated
user context. AGW2 will behave as anchor AGW for the user
session
4.
AGW2 forwards HO notification to BS2, with context transfer
to BS2
(3)
(6)
(11)
(7)
(2)
(5)
(4)
This allows BS2 to construct all user information
(10)
5.
BS2 responds to AGW2 that it is ready to receive new user –
sets up parallel tunnel to handle user (*depending on latency
requirements this can move later*)
6.
AGW2 forwards message back to source = AGW1, and starts
preparation for HO. Any tunnels between AGW1 and AGW2
get setup at this point. This tunnel would be to
forward/bicast traffic across to the Target BS before MSS
connects to the target.
7.
AGW1 forwards request to BS1
8.
BS1 responds back to user, asking to move to BS2
9.
User moves to BS2,
BS1
BS2
(1)
(8)
(9)
10. BS2 signals user successfully associated – to AGW2.
11. AGW2 signals to AGW1 to revoke previous connection.
12. AGW1 starts cleanup of previous path (BS1 – AGW1)
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PPP Free Operation (PFO)
 PFO, a key element of the evolved architecture,
 PPP is not designed for wireless as point of
attachment mobility and the need to maintain PPP
connection during a session imposes significant
challenges on the wireless network
 Also PPP doesn’t support smooth handoff as it
brings down all network-layer connectivity
whenever option renegotiation takes place
 Migrating PPP state information from old to new
AGW/PDSN at reneg/ handoff may fix the problem
but adds unnecessary complexity, and may require
business relationships between the home and
visited networks
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PPP Free Operation
Other reasons for PFO:
 PPP is not compatible with the emerging 3G services such as
Broadcast/Multicast services, etc
 Running CHAP over PPP is redundant since Mobile IP can be
used for access authentication
 For Mobile IPv4 NAI, authentication credentials, and dynamic
configuration of IP address are used for access authentication
while for Mobile IPv6 a layer 3 signaling mechanism can be
used for this purpose
 For Simple IP DHCP (instead of IPCP) can be used for IP
address assignment and configuration options negotiation
 Removing PPP dramatically improves network performance
including fast session setup, low handoff latency, lower
signaling overhead and load on AGW
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E2E QoS Design Goals …
 E2E QoS architecture should allow dynamic
resource allocation across multiple network
domains
 Lack of an E2E QoS solution increases costs due to
the need for multiple signaling conversions and
multiple bilateral agreements between carriers
 New service creation blocked by the complexity of
multiple, incompatible QoS signaling mechanisms
 E2E QoS allows IP applications to be developed
independent of the underlying access technology
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E2E QoS Signaling using RSVP
 RSVP as a layer 3 protocol provides a link layer
agnostic solution for E2E QoS
 RSVP-aware nodes are able to dynamically evaluate the
impact of the associated data traffic on network
resources and to notify upstream nodes of this impact
 RSVP is flexible and can be adapted to various network
configurations
 One can build hybrid topologies where RSVP is used in
the access network to protect the slower links while the
high speed backbone use DiffServ
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E2E QoS Signaling Framework
Application Level QoS
Signaling
Service
Domain 1
Service
Domain 1
Application Plane
MS
CN
Transport Plane
Transport
Domain 1
Transport
Domain 3
Transport
Domain 2
Packet Flow
QoS Signalling
Call Signalling
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Transport Level QoS Signaling
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(e.g., RSVP)
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Summary
3GPP2 network evolution should take into account the following
considerations:
 Incorporate LMA in the current layer 3 mobility framework to
improve network performance in terms of handoff latency, packet
loss and signaling traffic during location updates
 Allow PPP Free Operation to improve network performance
including fast session setup, low handoff latency, lower signaling
overhead and load on the AGW
 Make use of RSVP for the E2E QoS signaling
 A layer 3 protocol provides a link layer agnostic solution
 Can be adapted to various network configurations
 Combined Radio enhancements and network enhancements lead to
significant decreases in network delay and jitter making time
sensitive applications viable
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