Transcript Document

Diverse Network Services
and
Remaining Challenges
SRCCS Winter 2005
Workshop on
Internet Modeling and Analysis
Sue B. Moon
Division of Computer Science
Dept. of EECS
KAIST
Diverse Data Sets in Korea
• Data from major ISPs
– Non-existent in public
• Data from academia
– DAGMON traces at KAIST
– Long-term, sampled flow-level traces at POSTECH
– 4-month-worth NetFlow traces at CNU
• Others
– 3G video streaming service data
– 2-day packet-level traces from a home network
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Diverse Data Sets in Korea
• Data from major ISPs
– Non-existent in public
• Data from academia
– DAGMON traces at KAIST
– Long-term, sampled flow-level traces at POSTECH
– 4-month-worth NetFlow traces at CNU
• Others
– 2-day packet-level traces from a home network
– 3G video streaming service data
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2005.11.23 at KAIST
In Bits/Sec
No. of Pkts / sec
Others
Others
P2P
P2P
FTP
HTTP
FTP
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2004.12.9. at KAIST
In Bits/Sec
No. of Pkts / sec
Others
Others
P2P
P2P
HTTP
FTP
5
REMOVE after chat with SY
• Previous slides upstream or
downstream?
• According to JH Youn
– Upstream 70%/85% (Bytes/Pkts) p2p
– Downstream Web and VOD more dominant
that p2p.
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Home Networking in Korea
• Architecture
–
–
–
–
Simple, tree-like topology
To each home = 100ME
Internal links = 1GE
Outbound speed = OC-3 or up
• Reality in new apt complexes
– Control home appliances thru the net
• washing machine, gas stove, lights, heater/airconditioner, door
lock
• by PDAs at home or remotely by cellphones/web access
– Replace DSL/cable lines
– Will be "backbone" for home ubiquitous sensor network
• Need for remote monitoring
– Lack of resources
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2004.12.11.
at a Home Network
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Video Streaming over 3G
• Goals of Monitoring
– To satisfy every user:
• High revenue-generating customers
• More focus on per-user performance
• Challenges
– E2E performance segmented over cellular
and wired networks
– No integrated monitoring solutions yet
– No good metric for overall/single-user
performance
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Provisioning
for Interactive Streaming
• Interactive Streaming
– Not a driving force behind b/w
– A candidate for growing revenue
• Examples
– VoIP gradually taking over PSTN traffic
– Remote video viewing at door by cell
phone
– Online game traffic
• "Good" routing more important than
bandwidth
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Routing in the Internet
Inter-domain:
policy-based routing
Intra-domain:
shortest path routing
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Issues in "Good" Routing
• Misbehaving routing protocols
– BGP misconfigurations
– Pathological behaviors
– Frequent changes
• Even under normal circumstances
– Transient behaviors
– Inter/intra-domain routing not well
understood
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Scenario
for a Transient Routing Loop
In Normal Operation
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When a link fails, R1 is the
first to detect.
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R3 is updated before R2.
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Finally R2 is updated, and the
loop is resolved.
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CDF of Routing Loop Duration
in Time
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VoIP experimental setup
[Boutremans2002]
• Traffic injected in the network:
– 200 byte UDP packets
– every 5ms.
• Packets captured and timestamped
at end-systems.
• Traceroute runs continuously during
the experiment.
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Information Sources
• IS-IS & BGP listener logs
• Router logs from both ends of
“failing” links
• Controlled bi-directional VoIP traffic
between Reston and ATL
• SNMP data
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Delays (1 sec timescale)
~3.4ms
~2.6ms
3 links up
2 links down
2 links up
3 links down
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When the two interfaces went
down …
6.6 seconds
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When three links came back up
…
Traffic “black-holed”
for 0.975 seconds
For 30 secs packets
follow a shorter path
Traffic “black-holed”
for 1.745 seconds
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Approaches To Fix It
• Fine-tuning parameters
– Timer values [Alattinoglu2002]
• Modify Routing Protocols
– Suppress advertisement and perform local
rerouting using a backwarding table
[Lee04]
– Centralized path computation
[Feamster04,Rexford04]
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Our Approach
• Key Idea:
– Find disjoint overlay path and send duplicate
packets
• Assumptions
– Sender and receiver both within an AS
– Bidirectional link weights
– Extra income for extra b/w consumption
• Pros and cons
– Advantages
• No modification to current infrastructure
• Selective use by only those that need it
– Disadvantages
• Extra b/w consumption
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Basic Ideas
source
destination
candidate relay nodes!!!
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Resilient to Failures
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Future Work
• Answer questions raised about diverse
data sets
• Find best places for relay nodes in
Inter-domain
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BACKUP
Summary: Local
Convergence
Experimen
t
IS-IS
Convergence
Service
Disruptions
2 links down
5.1 sec
6.6 sec
17.6 sec
~ 0 sec
5.9 sec
8.0 sec
17.5 sec
0.95 sec
2 links up
3 links down
3 links up
• Convergence delay during failures hurts
more
• After IS-IS converges, extra delay due to
FIB update
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Causes and Open Questions
• Why only after 30 secs?
– spf-interval set to 30secs
• What caused the 1.745 secs disruption?
• Unknowsn in GSR architecture
• What is the right timescale to
propagate good news?
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