A System for Authenticated Policy-Compliant Routing

1
A System for Authenticated Policy-Compliant
Routing

• Barath Raghavan and Alex C. Snoeren
• UC San Diego

2
Routing Today

• ISPs perform wide-area routing through BGP
• Used to express local policy and traffic eng.
• Problem users cant express routing preferences
• Overlay routing / IP source routing
• Enables edge routing control
• Allows pooling of resources
• Problem may interfere with ISP policy and
  traffic engineering

3
Our system Platypus

• Loose source routing in which
• Users can pick their routes
• ISPs control placement of indirection points
• and authentication which enables
• ISPs to verify the policy-compliance of traffic
• Is easily accountable
• Delegation of source routing rights by users

4
An example
Local policy avoids customer route through C
Default route
ISP 1
ISP 2
20
10
H1
10
5
ISP 3
C
20
H2
5
Optimal route
C could forward traffic
5
The challenge

• How can C provide forwarding service?

H3
P
ISP 1
ISP 2
P
H1
Forwarding relationship
ISP 3
C
H2
OK
BAD
6
Our system Platypus
Packet explicitly sent through C
P
ISP 1
H1

• Negotiate contract
• Receive source routing info
• Stamp send packets

C
Indirection point to route through
7
Key building blocks

• Routing system providing basic connectivity
• Path discovery mechanisms / services
• Negotiation of business relationships
• Mechanism for authenticated loose source routing

8
Network Capabilities

• Specify a hop of the source route, including
• Point of indirection, called a waypoint
• The responsible party, called the resource
  principal
• Waypoints are
• Chosen by ISPs
• Specified by a routable IP address

Waypoint ID
Resource Principal ID
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Authentication
Requires asymmetry of information H1 must know
more than H3
H3
ISP 1
H1
Sniffer
C
Goal Distinguish between valid and invalid
packets
10
Authentication keys

• Each waypoint has one waypoint key k
• Each resource principal has a secret key s
• Derived from waypoint key using a keyed MAC
• Unique given a waypoint and a capability

Waypoint key k
Capability c
MAC
Secret s
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Packet Stamping
Capabilities
Waypoint ID
IP Header
Waypoint ID
Payload
Platypus Header
Resource Principal ID
Auth Info (Binding)
Auth Info (Binding)
Secret s
Invariant headers payload
MAC
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Packet Verification
Waypoint key k
IP Header
Capability c
Platypus Header
MAC
Payload
Temporal secret s
Secret s
Headerpayload
MAC
Binding b
Packet binding b

Forward
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Temporal secrets

• Temporal secret keys expire periodically
• Expiration allows for changing policies
• No time sync required
• Secret computation includes Key ID/time
• Enables expiration on order of clock drift
• Requires lookup of temporal secrets

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Key lookup

• DNS-based key lookup
• DNS reply contains encrypted secret
• No key distribution infrastructure required
• Key lookup as fast as DNS lookup

DNS query
DNS reply containing temporal secret
ISP 1
H1
Operates key server
C
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Delegation

• Users may pass out their capabilities
• How might they restrict others use?
• Capability delegation
• Principals can restrict capabilities
• Limits holder to destinations within an IP prefix
• Useful to ensure similar reverse paths

ISP 1
ISP 2
H1
Undesirable asymmetry
ISP 3
C
H2
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Implementation

• End-host based stamping/forwarding
• User-level and kernel module versions

900
850
800
750
Output Rate (Kpps)
700
650
Linux native forwarding
Platypus null forwarding
600
Platypus UMAC forwarding
550
500
500
600
700
800
900
1000
Input Rate (Kpps)
17
Per-packet latency

• Total per-packet time I/O time header
  processing
• I/O time 2 µs
• Worst-case header processing time lt 2 µs
• Header processing overhead

18
Deployment

• Incrementally deployable
• Does not require inter-ISP cooperation
• Loose source-routing based
• How might ISPs deploy Platypus?
• Where should they be placed?
• How many Platypus waypoints are needed?

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Measurement study
Nortel
Lulea
R
R
R
R
KAIST
R
ISP
R
R
R
R
R
R
R
Coloco
UCSD
20
Waypoint effectiveness (MCI)
180
UCSD-Lulea
160
UCSD-Lulea opt
UCSD-KAIST
UCSD-KAIST opt
140
Coloco-Lulea
Coloco-Lulea opt
UCSD-Nortel
120
UCSD-Nortel opt
100
Latency (ms)
80
60
40
20
0
2
4
8
16
32
64
128
256
512
1024
of waypoints
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Summary and future work

• Platypus provides
• Source routing with ISP control of waypoints
• Means for authenticating source routed packets
• Incremental deployment
• Flow-based Platypus with existing hardware
• New forwarding business model
• Anyone can sell/resell forwarding service
• Real-time pricing of capabilities

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Scalability

• Forwarding state
• Waypoints only need O(1) state
• Key lookup
• Lookup overhead is small (3 crypto operations)
• One key server 500,000 lookups / sec
• Per-principal accounting
• High speed approx. per-flow counters Kumar 04

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Platypus header format
4 bytes
Flags
Capability List Length
Capability List Pointer
Encapsulated Protocol
Version
Original Source Address
Final Destination Address
Waypoint Address
Resource Principal
Flags
Key ID
Binding
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Temporal secret computation

• For a capability c and waypoint key k
• s MACk(c.wayc.rp(((tgtgtn) 0xFFFFFFF0)
  c.id))
• The exception to this is at key ID wraparound
• (tgtgtn) is either incremented or decremented by 1

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Measurement results (QWEST)
180
UCSD-Lulea
160
UCSD-Lulea opt
UCSD-KAIST
UCSD-KAIST opt
Coloco-Lulea
140
Coloco-Lulea opt
UCSD-Nortel
UCSD-Nortel opt
120
100
Latency (ms)
80
60
40
20
0
2
4
8
16
32
64
128
256
512
1024
of clusters
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Measurement results (GBLX)
180
UCSD-Lulea
160
UCSD-Lulea opt
UCSD-KAIST
UCSD-KAIST opt
Coloco-Lulea
140
Coloco-Lulea opt
UCSD-Nortel
UCSD-Nortel opt
120
100
Latency (ms)
80
60
40
20
0
2
4
8
16
32
64
128
256
512
1024
of clusters
27
Measurement results (SPRINT)
180
UCSD-Lulea
160
UCSD-Lulea opt
UCSD-KAIST
UCSD-KAIST opt
Coloco-Lulea
140
Coloco-Lulea opt
UCSD-Nortel
UCSD-Nortel opt
120
100
Latency (ms)
80
60
40
20
0
2
4
8
16
32
64
128
256
512
1024
of clusters
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Example Virtual multihoming
ISP 1
ISP 2
Using Platypus, C can virtually multihome with
ISPs 1 and 3
ISP 3
Local ISP
C
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Example Affecting Inbound Traffic
ISP 1
ISP 2
Using Platypus, C can distribute delegated
capabilities that are restricted to send to
prefixes within C
ISP 3
C