Securing Access to Mobile Operator Core Networks
using IKEv2
16.1.2006
Author
Supervisor
July 24, 2016
Master’s Thesis
Pekka Nurmi
Joerg Ott
Agenda
• Background
• Methodology
• Security Protocols for IP Networks
• Operator’s Network Architectures
• Testing IKEv2 Implementations
• Feasibility in Operator’s Environment
• Conclusions
July 24, 2016
2
Background
• Amount and the value of the internet traffic grows
• Insecurity of the networks, risks grow
• IP based networks -> IP security (IPsec)
– Enhanced version of the IPsec defined by the IETF in
December 2005
• New key exchange protocol IKEv2
– more efficient
– more secure
• First implementations during 2006
– need for testing in Mobile Operator’s environment
” Is the IKEv2 based Virtual Private Networks (VPNs) feasible in
an operator’s network environment? ”
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3
Methodology
•
The study is conducted in three parts
1. Literature study
– Security protocols for IP networks (IETF)
– Operator’s network Architectures (3GPP)
2. Testing
– 3 Cases = 3 different IKEv2 implementations
– Measurements using network analyzer tools
3. Feasibility evaluation
– Operator solutions
– Issues and improvements
July 24, 2016
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Security Protocols for IP networks 1/3
IPsec
• creates VPN tunnels and provides
security for the insecure IP protocol
• access control, connectionless
integrity, data origin authentication,
confidentiality, and anti-replay
protection
Transport Mode
Client
Client
Internet
Tunnel Mode
PDG
Client
• Security protocols
– Encapsulating Security Payload
(ESP)
– Authentication Header (AH)
plain
Original IP
packet
Original IP
header
ESP in
Tunnel Mode
New IP header
TCP
Data
encryption
encr. + integrity
ESP
Original IP
header
• Key management
– Internet Key Exchange (IKEv2)
July 24, 2016
5
TCP
Data
ESP
trailer
ESP
ICV
Security Protocols for IP networks 2/3
IKEv2
• Key negotiation protocol for performing mutual authentication and
setting up IPsec security associations
• 4 message exchanges
– IKE_SA_INIT and IKE_AUTH
– CREATE_CHILD_SA
– INFORMATIONAL
MOBIKE
• IKEv2 Mobility and Multihoming protocol
• VPN client can move and change address without breaking the SA
• New protocol; no implementations tested yet
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Security Protocols for IP networks 3/3
IKEv2 authentication in operator’s network
• AAA protocol (RADIUS, Diameter)
• EAP-SIM
– SIM card based authentication
• EAP-AKA
– for 3G
Corporate Network (trusted)
AAA protocol
IKEv2 exchange
Carrying EAP
AAA Server
IKEv2 Initiator
VPN client
July 24, 2016
IKEv2 Responder
(VPN GW)
7
Operator’s Network Architectures 1/3
• Access Networks
– GERAN / UTRAN
3GPP Rel 6
Core Networks
– WLAN
UE
HSS
GERAN
CS domain
HLR
• Core Network
– CS & PS domains
BTS
BSC
MGW
UTRAN
AAA
PS domain
– AAA services
– IMS services
PSTN
MSC
Node B
IMS
RNC
SGSN
GGSN
Internet /
Intranet
MGCF
WLAN
CSCF
AP
July 24, 2016
Access
Router
MGW
WAG
PDG
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Operator’s Network Architectures 2/3
• IMS services using IKEv2
– Tunneled connection to the operator’s PDG
IMS
GGSN
RAN
IKEv2 exchange
WLAN
UE
PDG
CSCF
MGCF
BGCF
SGW
MGW
HSS
SLF
...
MGCF – Media Gateway Control Function BGCF – Breakout GCF
SGW – Security Gateway
CSCF – Call Session Control Function
SLF – Subscriber Location Function MGW – Media Gateway
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Operator’s Network Architectures 3/3
• Mobility management in IKEv2 (in 3GPP2)
– MOBIKE for intra Access Network handoff
– MIP for inter AN handoff
WLAN AN
MOBIKE
Core Network
Intra
AN
handoff
Inter
AN
handoff
MOBIKE
PDG
MIP
MIP
UTRAN
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Testing IKEv2 Implementations 1/3
• Case 1
– IP based solution
– laptop client (Linux)
• Case 2
– IP based solution
– Mobile phone client (Symbian
S60)
• Case 3
– 3G and IP based solution
(TTG)
– 2 clients
– Laptop (Windows XP)
AAA
server
PDG
WAG
WLAN
UE
TTG
Subset of
GGSN
functions
– PDA (Windows Mobile 5.0)
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IP
network
Testing IKEv2 Implementations 2/3
• Test Case Architectures
Internet
WLAN UE
(Case 1)
WLAN AN
FW / Router
PDG
AAA Server
Management
HLR
WLAN UE
(Case 2)
• Cases 1 & 2
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Testing IKEv2 Implementations 3/3
HLR
Internet
AAA Server
PD G
Management
WLAN UE
GGSN
WLAN AN
TTG
WAG / AC
WLAN UE
2G/3G Client
GERAN/
UTRAN
SGSN
DNS
2G/3G Client
• Case 3
July 24, 2016
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Testing IKEv2 Implementations 4/4
Measurement results
Client
Tested
services
test device
OS
WLAN option
integrated 3G/GPRS option
LAN option
interoperability options
cryptographic suites
simultaneous IKE SAs
WAP / Mobile TV
IMS / videoshare&IM
Case 1
Case 2
laptop
Linux
yes
no
yes
fair
4 + more
4
-
mobile phone
Symbian S60
yes
no
no
poor
1
1
X
-
Case 3
laptop
Windows XP
yes
yes*
no
poor
1
1
X
PDA
Windows Mobile 5.0
yes
yes
no
poor
1
1
-
* = works with specific vendor's 3G cards
ike_sa_init
ike_auth
radius/eap-sim
re-transmitted (avg)
time [s]
IKEv2 tunnel
avg size of
ike_sa_init
ike_auth
the packets
radius
[B]
all packets
total size
without re[kB]
transmissions
number of
the packets
Case 3
2
10
6
0
1.480
352
185
217
3.856
2
10
8
0
9.390
361
327
355
6.831
2
8
6+2
1
2.008
419
282
179
4.679
3.856
6.831
4.527
10
9
8
time [s]
Case 1* Case 2
7
6
RADIUS/EAP-SIM
5
IKE tunnel
4
3
2
1
0
Case1
Case2
Case3
* = uses ready-configured IMSI and HLR simulator
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Feasibility in Operator’s Environment 1/4
• Present Situation
– Approx. 86 % of organizations
(turnover >10M€) in Finland
used VPN solutions already in
2005.
– Nearly 70% of mobile workers
used VPN by 2006 in the U.S.
– IPsec is the most popular
VPN technology
100 %
80 %
IPsec
60 %
MPLS
MPLS/IPsec
40 %
SSL
20 %
0%
2003
2004
2005
2006
2007
– VPN business is centralized
between a few big vendors
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2008
Feasibility in Operator’s Environment 2/4
• Solution 1
– Hosted VPN access to an enterprise’s intranet
– Same service for the 3G and IP (e.g. WLAN) access
– SIM-card based authentication in both cases
2G/3G
Operator’s
network
UE
Any IP
access
network
SGSN
GGSN
Intranet
AAA Server
IKEv2 tunnel
PDG
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Feasibility in Operator’s Environment 3/4
• Solution 2
– Bundle several secure
network access elements in
one package
Operator’s customer package
– Laptop/mobile phone
– 3G and WLAN
– SIM-card
– IKEv2/IMS VPN client
– for enterpises and consumers
Mobile device
with
USIM-card reader
USIMcard
IKEv2/IMS
VPN client
Operator provides
Access
to intra-/
internet
July 24, 2016
GPRS/3G/
HSDPA/
WLAN
connectivity
PDG
AAA services
17
Operator’s
Network services
Feasibility in Operator’s Environment 4/4
•
Issues and Improvements
1. Choices for Clients
2. Interoperability
3. Mobility management
4. Signalling traffic optimization
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Conclusions
• Secure connections are needed
• IKEv2 and IPsec specifications provide enhanced IP
security
• IKEv2 implementations appear to be promising
technology
• A few important issues to solve with every tested
implementation
• IMS services can be used safely through an IKEv2
tunnel
• Large-scale scalability testing needed
• The old security solutions are still valid, but for how
long?
July 24, 2016
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July 24, 2016