Transcript Transporting Packets from End-to

Seminar on
“Clean Slate Design for the Internet”
Nick McKeown
[email protected]
1
High level
2

“Given what we know today, if we were to
start over with a Clean Slate, how would we
design a global communications network?”

“Ideally, how will the network look in 15-20
years, and how will we get there from here?”
Prelims
3

What’s wrong with the Internet…?

Why is the research and business community
not already solving it?

What are other groups doing?

What we plan to do at Stanford

An example of “Clean Slate” design
Original Architecture
4

A dumb connectionless packet-forwarding packetswitched infrastructure, with high-level functionality
at the edge

Single, simple lowest-common denominator data
delivery service (IP), with reliable stream service built
on top

Fixed-size numerical addresses with {network, host}
hierarchy; one per physical network interface

Later

Separation of IP and TCP (including congestion control
using packet loss as congestion signal)

Subnetting, autonomous systems (EGPs and IGPs), DNS,
CIDR
What is needed

Wouldn’t we like a network that we can trust to be
always there, always on, easy to use, universally
accessible, secure, and economically viable.

David Cheriton’s example: If the FAA carried all of its
traffic over the public Internet, you'd be nuts to fly.

Some obvious desirable characteristics

5

Robustness and Availability

Security

Naming and Addressing: accountability vs anonymity

Predictability

Mobility

Economic Viability
What else?
Prelims
6

What’s wrong with the Internet…?

Why is the research and business community
not already solving it?

What are other groups doing?

What we plan to do at Stanford

An example of “Clean Slate” design
Prelims
7

What’s wrong with the Internet…?

Why is the research and business community
not already solving it?

What are other groups doing?

What we plan to do at Stanford

An example of “Clean Slate” design
What are others doing?

8
Background

Incrementalism and “victim of success” of Internet

New era of more radical and fundamental thinking
about the future of networks and communications

New-arch (MIT)

100x100 (CMU)

Geni (NSF/Gov)
New-arch (2000)


9
Requirements for new network

Mobility: Highly dynamic and efficient

Policy-driven auto-configuration

Highly time-variable resources

Allocation of capacity
http://www.isi.edu/newarch/
100x100 (CMU/Stanford/Rice)

NSF Large ITR (2003-2008)

Questions:

10

Can structure be used to make networks more robust,
predictable and manageable?

What economic principles drive the operation of access and
backbone networks?

What security primitives must be built into the network?

Can/should network and protocol architectures be designed
to take advantage of long-term technology trends?
http://100x100network.org/
NSF Geni Initiative (2005)
11

CISE major effort, seeking congressional funding of
approx $300M starting 2008

Two parts: Research program; Global experimental
facility to explore new architectures

Areas of interest:

Creating new core functionality, including naming,
addressing, identity, management.

Developing enhanced capabilities: building security intot he
architecture; design for high availability;
privacy/accountability; design for regional differences and
local values

Deploying and validating new architectures

Building higher-level service abstractions

Building new services and applications

Developing new network architecture theories
Prelims
12

What’s wrong with the Internet…?

Why is the research and business community
not already solving it?

What are other groups doing?

What we plan to do at Stanford

An example of “Clean Slate” design
Prelims
13

What’s wrong with the Internet…?

Why is the research and business community
not already solving it?

What are other groups doing?

What we plan to do at Stanford

An example of “Clean Slate” design
What we plan to do at Stanford

Weekly Seminar in Fall and Winter


14
Fall: Talk by professor followed by discussion
Goals

To get thinking about the problem

To learn from each other

To identify some collaborative research projects
Prelims

What’s wrong with the Internet…?

Why is the research and business community
not already solving it?

What are other groups doing?

What we plan to do at Stanford

An example of “Clean Slate” design
How to design backbone networks from a clean slate?
15
Backbone Networks: Emerging Structure

10-50 routing centers interconnected by long-haul optical
links

Increasingly rich topology for robustness and loadbalancing

Typical utilization < 25%, because

16

Uncertainty of traffic matrix network is designed for

Headroom for future growth

Headroom to carry traffic when links and routers fail

Minimize congestion and delay variation
Efficiency sacrificed for robustness and low queueing delay
How flexible are networks today?
What fraction of allowable traffic matrices can they support?
Abilene
25% Over Prov: 0.025%
50% Over Prov: 0.66%
AT&T
25% Over Prov: 0.0006%
50% Over Prov: 0.15%
17
Verio
25% Over Prov: 0.0004%
50% Over Prov: 1.15%
Sprint
25% Over Prov: 0.0003%
50% Over Prov: 0.06%
Verio, AT&T and Sprint topologies are from RocketFuel
Desired Characteristics

Robust
Recovers quickly; continues to operate under failure

Flexible
Will support broad class of applications, new customers,
and traffic patterns

Predictable
Can predict how it will perform, with and without failures

Efficient
Does not sacrifice cost for robustness
18
Backbone Design

19
Assume underlying reliable mesh of physical
circuits
1.
Dynamic circuit switching over underlying mesh,
or
2.
Load-balanced logical network.
Describing today
Approach

Assume we know/estimate traffic entering
and leaving each Regional Network


Use Valiant Load Balancing (VLB) over whole
network

20
Requires only local knowledge of users and
market estimates
Enables support of all traffic matrices
Valiant Load-Balancing
2r1r2 /rN
r1
1
rN
r2
2
3
N
…
4
r4
Capacity provisioned over existing
robust mesh of physical circuits
21
r3
A Predictable Backbone Network



22
Performance: 100% throughput for any valid traffic
matrix.

Only need to know aggregate node traffic.

Under low load, no need to spread traffic.
Robustness

Upon failure, spread over working paths

Small cost to recover from k failures: Provision approx 2rirj/r(N-k)

Simple routing algorithm
Efficient

VLB is lowest cost method to support all traffic matrices

Similar cost, while supporting significantly more traffic matrices.
How expensive would VLB be?
Cost normalized to VLB routing.
Cost of switching = cost of transmission for 370miles
Abilene
25% Over Prov: 0.026% Cost: 0.87
50% Over Prov: 0.66% Cost: 1.04
AT&T
25% Over Prov: 0.0004% Cost: 0.94
50% Over Prov: 0.14%
Cost: 1.12
23
Verio
25% Over Prov: 0.0003% Cost: 0.99
50% Over Prov: 1.08%
Cost: 1.19
Sprint
25% Over Prov: 0.0002% Cost: 0.86
50% Over Prov: 0.04%
Cost: 1.04
Open questions

24
Worst case propagation delay doubled

Low variance in delay

There are “express paths”

(How) are multiple VLB networks connected,
and how does performance change?

Economics and policy: how do operators
compete?