15-441: computer networking lecture 26: networking future
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15-441: Computer Networking
Lecture 26: Networking Future
Lecture 26: 12-06-01 2
Overview
• Learning From Failures
• Changes in Various Layers
• New Services
• What Do I Work On?
Lecture 26: 12-06-01 3
Learning From Failures
• Past failures• Multicast• QoS• MobileIP
Lecture 26: 12-06-01 4
Why Did They Fail?
• Scalability problems
• Incremental deployment
• Interfacing with applications/Building useful services
• Debugging problems
• Conservative network administrators
Lecture 26: 12-06-01 5
What Can We Learn?
• Avoid same pitfalls
• Clever techniques• Fair queuing, announce/suppress protocols,
tunneling/encapsulation, etc.
Lecture 26: 12-06-01 6
Overview
• Learning From Failures
• Changes in Various Layers
• New Services
• What Do I Work On?
Lecture 26: 12-06-01 7
Link Layer
• Optical links• Multiple wavelengths on a single fiber (WDM)
• MPLS applied to wavelengths MPλS
• No longer broadcast
• All optical networks• No buffering!! How does this affect other
protocols
• Mobile/wireless links
Lecture 26: 12-06-01 8
Overlay Routing
• Basic idea:• Treat multiple hops through IP network as one hop in
overlay network• Run routing protocol on overlay nodes
• Why?• For performance – can run more clever protocol on
overlay• For efficiency – can make core routers very simple• For functionality – can provide new features such as
multicast, active processing, IPv6
Lecture 26: 12-06-01 9
IP Multicast
Key Architectural Decision:
Add support for multicast in IP layer
Berkeley
Gatech Stanford
CMU
Lecture 26: 12-06-01 10
Overlay Multicast
Stanford
Overlay Tree
CMU
Stan-LAN
Stan-Modem
Berk2
Gatech
Berk1
Berkeley
Gatech Stan-LAN
Stan-Modem
Berk1
Berk2
CMU
Lecture 26: 12-06-01 11
Overlay Challenges
• “Routers” no longer have complete knowledge about link they are responsible for
• How do you build efficient overlay• Probably don’t want all N2 links – which links to
create?• Without direct knowledge of underlying
topology how to know what’s nearby and what is efficient?
Lecture 26: 12-06-01 12
Congestion Control
• Is AIMD the right choice for everyone?• What are the requirements on choices TCP-
friendliness• Non-linear controls• Rate-based controls
• Fixing poor interaction with HTTP
Lecture 26: 12-06-01 13
Denial of Service
• Objective of attack: make a service unusable, usually by overloading the server or network
• Example: SYN flooding attack• Send SYN packets with bogus source address• Server responds with SYNACK keeps state about TCP
half-open connection• Eventually server memory is exhausted with this state
• Solution: SYN cookies – make the SYNACK contents purely a function of SYN contents, therefore, it can be recomputed on reception of next ACK
• More recent attacks have used bandwidth floods• How do we stop these?
Lecture 26: 12-06-01 14
Bandwidth DoS Attacks
• Possible solutions• Ingress filtering – examine packets to identify bogus
source addresses• Link testing – how routers either explicitly identify which
hops are involved in attack or use controlled flooding and a network map to perturb attack traffic
• Logging – log packets at key routers and post-process to identify attacker’s path
• ICMP traceback – sample occasional packets and copy path info into special ICMP messages
• IP traceback
Lecture 26: 12-06-01 15
Overview
• Learning From Failures
• Changes in Various Layers
• New Services
• What Do I Work On?
Lecture 26: 12-06-01 16
Network Location Service
• Desirable to lookup performance between hosts• Why?
• How to predict?• Based on historical measurements• Based on on-demand probing
• What exactly is performance?• Bandwidth• Delay• Application response
Lecture 26: 12-06-01 17
Services For Mobile Users
• Why?• (Example) Mobile users are more likely to
search for services near them• Not well suited to administratively organized Internet
systems
• Example• Build a wide area service discovery that can
support multiple search styles
Lecture 26: 12-06-01 18
Overview
• Learning From Failures
• Changes in Various Layers
• New Services
• What Do I Work On?
Lecture 26: 12-06-01 19
Three Project Areas
• Congestion Control • Solving interaction between HTTP and TCP • Using congestion control to implement QoS
• Mobile Networking • Making protocols adapt to dynamic conditions• Helping “ubiquitous” networks evolve• Sensor networks
• Wide-Area Distributed Applications• Tools to help developers build large distributed
applications• Overlay multicast
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