Cisco Group Encrypted
Transport VPN –
Technical Overview
December 2006
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Agenda
ƒ Problem Statement
ƒ Solution: Group Encrypted Transport
ƒ Technology Components
ƒ Feature Overview
ƒ Provisioning and Management
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Problem Statement
ƒ Today’s Enterprise WAN technologies force a trade-off
between QoS-enabled branch interconnectivity and transport
security
– Networked applications such as voice, video and web-based
applications drive the need for instantaneous, branch interconnected,
QoS-enabled WANs
– Distributed nature of network applications result in increased demands
for scalable branch to branch interconnectivity
– Increased network security risks and regulatory compliance have
driven the need for WAN transport security
– Need for balanced control of security management between
enterprises and service providers
ƒ Service providers want to deliver security services on top of
WANs such as MPLS without compromising their SLAs
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Solution: Cisco Group Encrypted Transport VPN
RR
CE 3
CE1
10/2
10/4
(10.1.1.1, 10.2.1.1)
(10.4.1.1, 10.3.1.1)
(10.3.1.1, 10.3.1.1)
IP VPN
(10.1.1.1, 10.2.1.1)
(10.3.1.1, 232.0.0.1)
(10.1.1.1, 10.2.1.1)
CE 4
CE 2
Key
Server
(10.4.1.1, 10.3.1.1)
Branch
ƒ Encrypted Any-Any
connectivity
Enterprise Core
ƒ Any-to-Any Connectivity
ƒ Hierarchical Routing
(without tunnels)
ƒ Redundancy Established
by Core Routers
ƒ Native QoS support
ƒ Core for Multicast
Replication
ƒ Native Multicast
Encryption
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10/1
(10.3.1.1, 232.0.0.1)
10/3
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10/5
Branch
ƒ Transparent Service
Integration (e.g.,MPLS)
ƒ Integration with DMVPN
ƒ Highly Scalable Full Meshes
ƒ Monitoring/Management:
centralized policy
distribution CLI/GUI
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Benefits of Cisco GET VPN
Previous Limitations
New Feature and Benefits
Multicast traffic encryption through Encryption supported for Native Multicast and
IPsec tunnels:
Unicast traffic with GDOI
– Not scalable
– Allows higher scalability
– Difficult to troubleshoot
– Simplifies Troubleshooting
– Extensible standards-based framework
Overlay VPN Network
– Overlay Routing
– Sub-optimal Multicast
replication
– Lack of Advanced QoS
No Overlay
– Leverages Core network for Multicast
replication via IP Header preservation
– Optimal Routing introduced in VPN
– Advanced QoS for encrypted traffic
Full Mesh Connectivity
– Hub and Spoke primary
support
– Spoke to Spoke not scalable
Any to Any Instant Enterprise Connectivity
– Leverages core for instant communication
– Optimal for Voice over VPN deployments
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Cisco GET VPN: Before and After
Before: CE-CE Protection with Peer-Based Model
After: CE-CE Protection with Group-Based Model
Multicast Source
Multicast Source
VPN A
VPN A
VPN A
VPN B
VPN A
VPN A
VPN B
VPN A
Multicast in the core
VPN A
VPN A
MPLS VPN Network
MPLS VPN Network
VPN B
VPN B
VPN B
VPN B
GRE Tunnels
CE-CE
VPN B
VPN A
Multicast VRF
VPN B
VPN A
Multicast
Source
VPN B
Multicast Source
VPN B
• Scalability – an issue (N^2 problem)
• Highly Scalable Model
• Any-Any Instant Connectivity a issue
• Any-Any instant connectivity with Security
• Overlay Routing
• No Overlay Routing
• Multicast replication inefficient
• Efficient Multicast replication
• Unable to Leverage Advanced QoS
• Standards based advanced QoS
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Customer Deployment Scenarios
Customers for Cisco GET VPN fall into two categories:
Enterprises Purchasing Private WAN (e.g. MPLS) Connectivity from SP but wanting to
manage encryption themselves
Key Targets
ƒ Meet security policy or regulatory requirements
ƒ Want to self-manage VPN keys and group policies
SP Managed CPE/Security Services ( SP selling connectivity, security services to
Enterprises, commercial etc). SP manages GET VPN
ƒ Meet security policy or regulatory requirements
ƒ Complete outsourcing of branch office CPEs, group policies and VPN key management
For Enterprise IPSec VPNs (over public Internet)
Additional
Value
Enhances DMVPN and GRE-based S-S VPNs by:
ƒ Providing manageable, highly scalable meshing capability very cost-effectively
ƒ Simplifies key management in larger deployments
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Site-to-Site VPN Portfolio
Positioning & Differentiators
When to
Use?
GET VPN
DMVPN
IPSec (P2P/GRE)
Easy VPN with VTI
Existing Private WAN
(FR/ATM)
Replacement for, or existing
FR/ATM WAN
Encryption on IP VPN w/o
Tunnels
Alternative/Backup WAN
Replacement
for/Existing Traditional
FR/ATM WAN
Replacement
for/Existing Traditional
FR/ATM WAN
Alternative/Backup
WAN
Alternative/Backup
WAN
Encryption of pipe
Simplifies configuration
for hub & spoke VPNs
High Scale Hub/Spoke
for IPsec (Low Scale for
GRE)
High Scale Hub/Spoke
Virtualized WAN infrastructure
Virtualized WAN infrastructure
What it
Does?
Provides scalable, full-time
any-any secure connectivity
Simplifies configuration for
hub & spoke VPNs
Enables participation of
smaller routers in large
meshed networks
Provides low-scale, ondemand meshing
Simplified key management
Any Scale Hub/Spoke
High Scale Hub/Spoke
Any Scale Mesh
Low Scale Meshing
Native
Multicast
Yes
No – treats like unicast traffic
by tunneling it
No – treats like unicast
traffic by tunneling it
No – treats like unicast
traffic by tunneling it
Dynamic
Routing
Yes– No need for overlay
Routing
Yes—with Overlay Routing
Yes for GRE (with
Overlay routing)
No – not supported
Failover
Method
Routing based
Routing based
Stateful Failover
Stateful Failover
QoS
Yes
Yes
Yes
Yes
Keys
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Group-based
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Peer-based
Peer-based
Peer-based
Scale
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Technology
Components
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Group GET VPN
Concepts and Relationship
ƒ Key Distribution GDOI--Key distribution
mechanism (RFC3547)
Group Keys/Keys between Peer
Encrypted Control Plane
Data Protection
Secure
Multicast
ƒ Routing Continuity
No overlay Routing
Key Distribution
Group Domain
Of Interpretation
ƒ Multicast Data Protection
Routing
IP Header
Preservation
Encrypt Native Multicast
Replication in the core based on (S,G)
ƒ Unicast Data Protection IPSec is a
well-known RFC (RFC2401)
Encrypt Unicast with IPsec
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Data Protection
Secure
Unicast
10
Secure Key Distribution
ƒ Multicast and Unicast
Control Plane:
Group Domain of Interpretation (GDOI)
Group
Member
Group
Member
3
1
GDOI--Key distribution
mechanism
Reke
y SA
Subnet
– RFC 3547
Subnet
Subnet
IPSe
c
SAs
Group
Memb
er
Private
WAN
IPSe
c
Reke
y SA SAs
Reke
y SA
Subnet
4
2
IPSe
c
Reke
y SA SAs
– Group Keys
– Unicast/Multicast Key
distribution
– Cooperative Key Server for
High Availability
IPSe
c
SAs
Keys
and
RekeyPolicy
and
Policy
Group
Member
Key
Server
Reduces State Complexity
– Secure Control Plane via
Encryption
GSA*
GDOI
* GSA = Group Security Association
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Routing Continuity:
IPsec Tunnel Mode with IP Header Preservation
Original IP Packet
IP header
IP Payload
IPSec Tunnel Mode
New hdr with
Original IP hdr
encapsulated
Original source and destination IP address
encapsulated in tunnel mode
IP Payload
IP Header Preservation
GET
VPN
Original header
preserved
ESP header
IP
IP Payload
This mode is already necessary when encrypting IP multicast packets in order to
preserve the (S,G). Mitigates the requirement for a routing overlay network
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Secure Multicast
Data Protection
Multicast
Receiver
Key Server
Multicast
Sender
GM
IP
Internet
GM
GM
Multicast
Receiver
Group Member (GM)
ƒ Legitimate group members obtain Traffic Encryption Key from key server for
the group
ƒ Multicast Sender Encrypts Multicast with IP Address Preservation
ƒ Replication of Multicast packet in the Core based on original (S,G)
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Secure Unicast
Data Protection
Multicast
Host
Key Server
Multicast
Host
!!
IP
GM
!!
!!
GM
Multicast
Host
GM
GM
ƒ Group member assumes that legitimate group members obtain Traffic Encryption
Key from key server for the group
ƒ Group members can authenticate the group membership
ƒ Group member Encrypts Unicast with Group SA
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Detailed Feature
Overview
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Group Encrypted Transport Enabled VPN
Features
ƒ Key Management
– GDOI Registration/Rekey
– Unicast and/or Multicast Key Distribution
– Cooperative Key Server for High Availability
ƒ Policy Management
– Centralized Policy Distribution from PRIMARY Group Controller Key
Server
– Group Member Policy Exception (e.g. local deny)
– Group Member Policy Merge (concatenate KS policy with GM
policy)
ƒ IPSec Data Plane
– IPSec Tunnel Mode with IP Address Preservation
– Passive Security Associations for Graceful Roll-out (i.e. Receive
Only SA)
– Pseudo-time Synchronous Anti-Replay Protection
ƒ Enhanced Debugging (fault isolation)
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GDOI Registration
Key Distribution
Key Server
IPSec
SAs
Rekey
SA
Group Member 10.0.3.0/24
IPSec
SAs
Rekey
SA
IP
10.0.1.0/24
IPSec
SAs
Rekey
SA
Group Member
Group Member
IPSec
SAs
Rekey
Group Member
SA
10.0.2.0/24
ƒ Each router registers with the Key Server.
ƒ Key Server authenticates the router, performs an authorization check.
ƒ Key Server downloads the encryption policy and keys to the router
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GDOI Rekey
Key Distribution
Key Server
IPSec
SAs
IPSec
SAs
IP
10.0.1.0/24
IPSec
SAs
Group Member
Group Member
Group Member
IPSec
10.0.2.0/24
SAs
ƒ The key server generates and pushes new IPsec keys and policy
to the routers when necessary
ƒ Re-key messages can also cause group members to be ejected
from the group
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Multicast / Unicast Key Distribution
ƒ Multicast Key Distribution over
Multicast Enabled Network
–Via Multicast Formatted Key Message
and Network Replication
–Fallback to Group Member GDOI
Unicast Registration
KEK = 235687404
Multicast
enabled
WAN
Protect: 10.0.0.0/8 to 10.0.0.0/8
Group Member = 192.168.3.4
Group Member = 192.168.3.2
Group Member = 192.168.3.3
KEK = 235687404
ƒ Unicast Key Distribution over
non-Multicast Enabled Network
IP
Protect: 10.0.0.0/8 to 10.0.0.0/8
Group Member = 192.168.3.4
Group Member = 192.168.3.2
Group Member = 192.168.3.3
–Via per-Peer Unicast Formatted Key
Message
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Cooperative Key Server
Key Distribution
Multicast Key
KEK = 4596738459604
ƒ Primary Key Server
designated per Group
ƒ Multiple Secondary Key
Servers per Group
ƒ Synchronization of Policy
Database for Graceful Failover
Protect: (*,232.0.0.0/8)
Group Member = 192.168.3.4
Group Member = 192.168.3.2
Group Member = 192.168.3.3
Secondary KS
Key Server
KEK = 235687404
Secondary KS
Protect: 10.0.0.0/8 to 10.0.0.0/8
Group Member = 192.168.3.4
Group Member = 192.168.3.2
Group Member = 192.168.3.3
IP
10.0.1.0/24
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10.0.2.0/24
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Policy Management
ƒ Local Policy Configured by Group Member
ƒ Global Policy Configured and Distributed by Key Server
ƒ Global Policy Appended to Local Policy
Key Server
Permit: Any-Any
GM
10.0.3.0/24
10.0.1.0/24
IP
Deny: Link Local
GM
GM
Deny: Link Local
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10.0.2.0/24
GM
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Pseudo-Synchronous Anti-Replay
Example
ƒ Replay Based on
Synchronization of Pseudotime Across Group Members
ƒ Key Server Manages Relative
Clock Time (not Universal
Clock Time)
ƒ Group Members Periodically
Re-sync Pseudo-time with
every Rekey
ƒ No Existing Fields in IPSec
Header are Viable for Pseudotime (while maintaining IPSec
compliance)
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Reject
Initial
pseudotime
Accept
PTr - W
PTr
Reject
PTr + W
Anti-replay window
• If Sender’s PseudoTime falls in the
below Receiver window, packet
accepted else packet is discarded
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Design
Scenarios
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Cisco GET VPN
Critical Design Considerations
ƒ Encryption standard?
DES, 3DES, AES
ƒ Any-to-any requirements?
Yes, any-to-any traffic
ƒ IKE Authentication type?
Pre-shared Keys (PSK), X.509
Digital Certificates (PKI)
ƒ Additional Enterprise
Security Requirements?
Group Authentication
User Authentication
ƒ Addressing of remote
routers?
Static IP addresses or dynamic
ƒ Scalability?
10’s, 100’s, or 1000’s of branches
ƒ Aggregate bandwidth and
throughput requirements?
ƒ QoS requirements?
LLQ, Traffic Shaping, interface
level, per-VPN tunnel
ƒ IP Multicast applications?
DS3, multi DS3, OC3, OC12,
OC48
ƒ Traffic Mix?
pps, bps and packet size
Natively Multicast Encryption
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Cisco GET VPN
General Design Considerations
Applications (e.g. Voice, Video)
Group
Member
Hub Site
Number of
Routing Peers
WAN
Router
Number of
Branches
…
Other services
provided by
hub (e.g. FW,
IPS, QoS)
Key
Server
Service Provider(s)
Multicast enabled
network
Number of
Concurrent
IKE registrations
WAN
Aggregation
Circuit Speed
Group
Member
Anticipated
Utilization
Branch
Access Speeds
ƒ Proper Addressing is an absolute must to have easier policies
ƒ HW Encryption modules required and recommended
ƒ Routing protocols do not require a tunneling protocol
ƒ "pre-fragmentation" and "ignore the DF bit" should be set on the GET VPN
devices
ƒ Summarize Routes
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Group Encrypted Transport in Enterprise/SP WAN
Scenarios
Enterprise owned CPE, CE-CE with GET
Encryption,
KS Managed by Enterprise
Group
Group
Member
Managed CPE with GET Encryption, with
KS Managed by Enterprise
Member
Subnet 1
Private
Network
IPSec
SAs
Rekey
SA
Subnet 4
Rekey
SA
Rekey
Keys and
Policy
Rekey
SA
Rekey
Keys
and
Policy
Key Server
IPSec
static map
Primary DMVPN tunnel
Secondary DMVPN tunnel
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static
p2p GRE
with NHRP
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Group
Member
IPsec
Keys
and
Policy
Key
Server
Hosted GET, with KS Managed by SP
Managed
Key Server
Corp A
Site 3
Corp A
Site 2
IP/MPLS
Network
EIGRP
Corp A
Site 1
MPLS VPN – Corp A
Corp B
Site 2
MPLS VPN – Corp B
…
NHRP
DMVPN DMVPN
EIGRP
tunnel
protection
Subnet
4
Subnet
2
IPSec
SAs
Group
Member
DMVPN (mGRE over IPSec) with GET
multipoint
GRE
IPSec
SAs
Rekey
SA
Group
Membe
r
Subnet 2
IPsec
Keys and
Policy
Rekey
SA
Rekey
SA
Rekey
SA
Group
Member
IPSec
SAs
WAN
IPSec
SAs
IPSec
SAs
IPSec
SAs
Subnet
3
Subnet
1
IPSec
SAs
Rekey
SA
Group
Member
Group
Member
Subnet 3
NHRP
Corp B
Site 3
Corp B
Site 1
CPE-CPE
CPE-CPE Encryption
Encryption w/o
w/o Tunnels
Tunnels
Group-SA
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Provisioning and
Management
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Management of Cisco GET VPN
ƒ Centralized Provisioning by pushing keys and policies from Key Server
ƒ Secure Device Provisioning (SDP) available to bootstrap Group
Member configurations when using public key infrastructure (PKI)
ƒ SDP support available in both CSM and SDM
ƒ CSM Flex-Config for both Key Server and Group Member-provisioning
ƒ Cisco IOS Command-line interface available for provisioning,
monitoring, and troubleshooting
ƒ Cisco IOS NetFlow support for Monitoring of GET VPN traffic
ƒ DMVPN with Group Encrypted Transport can be configured with
CSM
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Fault Isolation
ƒ Show and Debugging capabilities for Key server
show crypto gdoi ks, debug crypto gdoi ks
ƒ Show and Debugging capabilities for Group Member
show crypto gdoi gm, debug crypto gdoi gm etc
ƒ Multi-level Debug/Fault Isolation capabilities for various
user roles e.g.
debug crypto gdoi error
debug crypto gdoi terse
debug crypto gdoi customer
debug crypto gdoi engineer
debug crypto gdoi packet
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DMVPN with Group Encrypted Transport
“Bootstrap” Provisioning of Remote Routers
Linux, MAC, MSWindows PC
1. Remote routers “call home”
and management tunnel is
set up
WLAN/TKIP
2. Management server
authenticates remote router
using certificate authority
and AAA servers
3. Management server pushes
policy including new
certificate
1. Call Home
ISP
5. Secondary Tunnel
4. Data Tunnel
3.
Data
VPN
Gateway 2
Policy Push
Data
VPN
Gateway 1
Management
VPN Gateway
Access to
Corporate
Resources
ISC, IE2100
Certificate
Authority,
AAA
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Internal
Network
2. Authenticate
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4. Remote router establishes
primary tunnel (DMVPN)
and access to corporate
resources
5. Secondary tunnel (DMPVN)
is established and stays
active for instant failover
6. Use flex-config on CSM to
provision Group members in
GET VPN
SDP:
Secure Device Provisioning
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Summary
ƒ Enterprise WAN technologies previously forced a
trade-off between QoS-enabled branch interconnectivity and
security
ƒ Cisco introduces Group Encrypted Transport (GET) VPN, a
next-generation WAN security technology:
Easy-to-manage, high-scale, any-to-any encrypted communications
Secured packets use existing WAN-agnostic routing infrastructure without
tunnels
Networkwide QoS and Multicast capabilities preserved; improves application
performance
Offers flexible span of control among subscribers and providers
ƒ GET VPN’s group-key mechanism simplifies key management
and reduces latency, improving any-to-any connectivity
capabilities
ƒ IP header preservation prevents overlay routing
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