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Robust Congestion Control for IP Multicast

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In-band distribution of keys from the sender to eligible receivers ... Solution: keys reuse components from lower groups ... addresses and keys to edge routers ... – PowerPoint PPT presentation

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Title: Robust Congestion Control for IP Multicast


1
Robust Congestion Control for IP Multicast
  • Sergey Gorinsky
  • Applied Research Laboratory
  • Department of Computer Science and Engineering
  • Washington University in St. Louis
  • November 3, 2003

2
The Internet Growth and Its Implications
  • Evolution of the Internet
  • Original design
  • Small test bed. Close-knit scientific community
  • Todays reality
  • Global commercial network. Large number of
    selfish users
  • Need to rethink assumptions in the Internet
    design
  • Network bandwidth allocation
  • Traditional assumption of universal trust
  • Misbehavior incentives unfairly high acquisition
    of bandwidth
  • Misbehavior opportunities open-source operating
    systems

Challenge robust allocation of network bandwidth
in distrusted environments
3
This Talk
  • Focus
  • Robust congestion control for multicast services
  • Outline
  • Background
  • Congestion control and multicast services
  • Trust model
  • Self-beneficial attacks by a receiver
  • Vulnerabilities of existing multicast protocols
  • Robust mechanisms for multicast congestion
    control
  • DELTA and SIGMA
  • Conclusion and future work

4

Congestion Control
  • Congestion
  • Excessive transmission results in packet losses
  • Uncontrolled retransmission leads to congestion
    collapse
  • Congestion control
  • Allocation of bandwidth along network paths
  • Prevention of congestion collapse
  • Responsiveness to congestion
  • Efficient utilization
  • Fair sharing
  • Unicast TCP congestion control Jacobson 1988
  • Receiver acknowledges delivered packets
  • Sender adjusts its transmission in response to
    feedback

5
One-to-Many Communications
  • Dissemination of data to multiple receivers
  • Example
  • Video address by the CEO of an international
    company to employees
  • Inefficient solutions
  • Direct unicast from the sender to each receiver
  • Broadcast
  • Multicast
  • Hierarchy for data duplication and forwarding
  • Implementations
  • IP multicast router-based hierarchy Deering
    1991
  • End-system multicast host-based hierarchy Chu
    2000

6
Supporting Scalable IP Multicast
Sender
Receiver
Receiver
Receiver
  • Receivers subscribe to a multicast group at
    their local edge routers
  • Receivers provide the sender with limited
    feedback
  • RMTP Paul 1997, SAMM Albuquerque 1998, pgmcc
    Rizzo 2000, TFMCC Widmer 2001

7
Addressing Receiver Heterogeneity
Sender
1 Mbps receiver
1 Mbps receiver
4 Mbps receiver
  • A multicast session is composed of multiple
    groups
  • Layered multicast RLM McCanne 1996, FLID-DL
    Byers 2000, WEBRC Luby 2002
  • Replicated multicast DSG Cheung 1996

8
Talk Outline
  • Background
  • Congestion control and multicast
  • Trust model
  • Self-beneficial attacks by a receiver
  • Vulnerabilities of existing multicast protocols
  • Robust mechanisms for multicast congestion
    control
  • DELTA and SIGMA
  • Conclusion and future work

9
Trust
Existing protocols
Sender
Receiver
Receiver
Receiver
10
Types of Bandwidth Attacks
  • Denial-of-service attacks
  • Disruption of network services
  • Intentionally visible
  • Self-beneficial attacks
  • Acquisition of data at an unfairly high rate
  • Intentionally keeping a low profile
  • Easy to launch
  • TCP Daytona Savage 1999, throughput
    improvement tools
  • Dangerous

Our focus self-beneficial bandwidth attacks
11
Vulnerabilities of Multicast Protocols
12
Inflated Subscription in FLID-DL
One bottleneck link shared by six sessions two
FLID-DL and four TCP
Inflated subscription is a fundamental threat to
fair bandwidth allocation
13

Protection against Inflated Subscription
  • Source of inflated subscription ability to join
    any group
  • Solution congestion-dependent group access
    control
  • Access rights are a function of the congestion
    status
  • Access keys change every time slot
  • Requirements
  • Minimal generic changes in the network
  • Support of existing and future multicast
    protocols
  • Preservation of congestion control properties

14
Linkage of Access Rights with the Congestion
Status
Packets
Sender
15

Robust Group Subscription DELTA and SIGMA
  • DELTA (Distribution of ELigibility To Access)
  • In-band distribution of keys from the sender to
    eligible receivers
  • Transforms a vulnerable multicast protocol into
    its robust version
  • Requires a protocol-specific instantiation
    dependent on
  • Congestion notification
  • Session structure
  • Congested state
  • Subscription rules
  • SIGMA (Secure Internet Group Management
    Architecture)
  • Generic distribution of keys from the sender to
    edge routers
  • Key-based group access control at edge routers

16
Example of a Protected Protocol
  • Session structure
  • N cumulative subscription levels
  • First level group 1 (base layer of data)
  • Second level groups 1 and 2 (two lower layers
    of data)
  • N-th level all N groups of the session (all
    layers of data)
  • Congested state of a receiver
  • Single packet loss in any of the subscribed
    groups
  • Subscription rules
  • Rule 1 Congested receiver must drop its top
    group
  • Rule 2 Receiver can preserve its lower groups

17
Rule 1 Congested Receiver Must Drop Its Top Group
Packets of group 4

Packets of group 3
Packets of group 2
Packets of group 1
Time slot
  • Problem each packet of group 1 carries N
    components
  • Reason different keys use independent
    components

18
Rule 1 Congested Receiver Must Drop Its Top Group
Packets of group 4

Packets of group 3
Packets of group 2
Packets of group 1
1
2
3
4
5
Time slot
  • Packets of a subscription level carry
    components of a key for its top group
  • Problem each packet of group 1 carries N
    components
  • Reason different keys use independent
    components
  • Solution keys reuse components from lower
    groups

19
Rule 2 Receiver Can Preserve Its Lower Groups
Packets of group 4

Packets of group 3
Packets of group 2
Packets of group 1
Time slot
  • Top key for each group g
  • Solution decrease key and top key for each
    group are different

20
Rule 3 Authorized Uncongested Receiver Can Add
Group
Packets of group 4

Packets of group 3
Packets of group 2
Packets of group 1
Time slot
  • Increase key for each authorized group

where is XOR, is a component in
packet p of group j
21
Generalizing the Solution
  • Above example of DELTA instantiation
  • Protected protocol
  • No support for reliable delivery
  • Loss-driven detection of congestion
  • Layered multicast
  • Single-loss definition for the congested state
  • Protection against individual attacks
  • Extensions
  • Protection against collusion attacks
  • DELTA instantiations for other types of protocols

22
DELTA Instantiations for Different Types of
Protocols
  • Reliability
  • Reliable protocols (vs. unreliable protocols)
  • Sender distributes components among both original
    and additional packets
  • Congestion notification
  • ECN (vs. loss)
  • Edge routers change the component in each marked
    packet
  • Session structure
  • Replicated multicast (vs. layered multicast)
  • Keys consist of components from a single group
  • Congested state
  • Loss rate exceeding a threshold (vs. single
    packet loss)
  • n packets are transmitted to a subscription level

23

SIGMA
  • Distribution of keys from the sender to edge
    routers
  • Challenge generic network support
  • DELTA-style reconstruction of keys from
    components is protocol-specific
  • Solution multicast of group addresses and keys
    to edge routers
  • Special packets carry address-key tuples
  • Edge routers intercept these packets
  • Forward error correction provides reliable
    delivery
  • Key-based group access control at edge routers

24

Group Access Control in SIGMA
  • Operation timeline
  • New challenges in group management
  • Adding a group
  • Unconditional access to the added group for two
    consecutive time slots
  • Admitting a new receiver into the session
  • Intermittently unrestricted access to the minimal
    group

25
Protection against Inflated Subscription
26
Preservation of Congestion Control Properties
Responsiveness
Efficiency
DELTA and SIGMA preserve congestion control
properties
27
Research Summary
  • Relaxed the traditional assumption of universal
    trust in multicast congestion control
  • Focused on self-beneficial attacks of misbehaving
    receivers
  • Classified and demonstrated vulnerabilities in
    multicast protocols
  • Designed protection against inflated subscription
  • DELTA and SIGMA congestion-dependent group
    access control
  • Generic network support
  • Robustness to individual attacks (and extension
    for collusion attacks)
  • Robust adaptation of FLID-DL (and RLM) protocols

28
Future Work
  • Robust bandwidth allocation in peer-to-peer
    multicast
  • Routing with misbehaving receivers
  • New types of attacks
  • Eliciting a self-beneficial multicast hierarchy
  • Slow forwarding

Trusted base
Sender
Receiver
Receiver
Misbehaving receiver
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