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