Transcript Pastry: Scalable, decentralized object location and

Is IP going to take over the
world (of communications)?
Pablo Molinero-Fernandez, Nick McKeown Stanford University
Hui Zhang
Turin Networks, Carnegie Mellon University
Alan Mislove, Ansley Post COMP 629 1.22.2004
Background

The Internet is one of the most successful
communications platforms
 Seen

exponential growth in the past decade
Almost all Internet traffic is over Internet Protocol
(IP)
 Designed

in 1970s through DARPA funding
IP’s great success due to
 Reachability
 Heterogeneity
Alan Mislove, Ansley Post COMP 629
1.22.2004
Background (cont.)

Success has lead to the assumption that IP will
become the sole communication platform
 Voice-over-IP
systems will replace phone network
 TV, Movies will be disseminated using Internet

Related assumption is that packet-switching (IP)
routers will become the only type of switching device
Alan Mislove, Ansley Post COMP 629
1.22.2004
Motivation

IP is technically able to support all types of
applications
 Request-reply
(web traffic)
 Real-time (telephony)

Despite its strengths, not necessarily the best
solution

Goal: Question previous assumptions that IP will
“take over the world (of communications)”
 Evaluate
what would happen if we started over
Alan Mislove, Ansley Post COMP 629
1.22.2004
IP Folklore

There are many widely held assumptions (“sacred
cows”) about IP that must be reevaluated
 The
current dominance of IP for communications
 The efficiency of IP
 The robustness of IP
 The simplicity of IP
 IP’s suitability for real-time applications
Alan Mislove, Ansley Post COMP 629
1.22.2004
IP Communications Dominance

It is widely (and incorrectly) believed that IP already
dominates global communication
 ISP
markets have revenues of $13B
 Other communication markets total over $300B

For data and telephony applications alone, IP
routers total $4B, while circuit-based router total
$32B

Internet reaches 59% of US, phone 94%, TV 98%
Alan Mislove, Ansley Post COMP 629
1.22.2004
IP’s Efficiency

IP makes efficient use of scarce bandwidth
 Very
good for wireless channels, satellite links, etc…
 But is bandwidth actually scarce?

Average Internet link utilization is 3%-20%
 LAN
usage is much lower, about 1%
 Long-distance phone utilization is 33%

Networks are highly overprovisioned to provide a
consistent user experience
 Low
packet delay is the goal
Alan Mislove, Ansley Post COMP 629
1.22.2004
IP’s Efficiency (cont.)

Many reasons given for overprovisioning
 Internet
traffic is asymmetric and bursty
 Difficult to predict traffic growth on a link
 Economical to add large increments of capacity

However, there are “less talked-about” reasons
 Under
congestion, IP performs badly
 Control traffic transmitted in-band
 Results in black holes, loops, etc…

Much easier to keep utilization low
Alan Mislove, Ansley Post COMP 629
1.22.2004
IP’s Efficiency (cont.)

In practice, user experiences the same delay in
packet-switched or circuit-switched network

Average user’s work (65%) is request-response
 Web
traffic
 File sharing

For these types of workloads, circuit-switching
provides same user response time
Alan Mislove, Ansley Post COMP 629
1.22.2004
IP’s Robustness

Internet was designed to withstand catastrophic
event, but
 Median
Internet downtime is 471 minutes/year
 Median phone downtime is 5 minutes/year

BGP convergence is slow (3-15 minutes)
 SONET/SDH

switches to a backup path in 50ms
Nothing inherently unreliable about circuit-switching
Alan Mislove, Ansley Post COMP 629
1.22.2004
IP’s Simplicity

Beginning principle is that complexity should be at
the endpoints
 Increasingly,




IP routers have become sophisticated
Multicast
Quality of Service
VPN
Configuring IP routers can be very difficult
 Single
misconfigured IP router can cause instability
for a large portion of the network
Alan Mislove, Ansley Post COMP 629
1.22.2004
IP’s Simplicity (cont.)

Circuit-switched routers have 3 million lines of code
 IP

routers have about 8 million
IP routers have 300 million gates, 1 CPU, 300 MB of
buffer space
 Circuit
routers have 25% of the gates and no CPU

Circuit-switched routers sell for 1/2 - 1/12 the price

Circuit switching is compatible with optical
technology
Alan Mislove, Ansley Post COMP 629
1.22.2004
IP’s Real-Time Support

Widely held assumption that IP will support real-time
applications
 This
assumption relies on overprovisioning of the
network
 Or quality-of-service in the network that has yet to be
implemented
Alan Mislove, Ansley Post COMP 629
1.22.2004
What if we started over?

Hybrid solution would be most appropriate
 Uses
packet switching at the edges
 Circuit-switching at the core and with applications with
QoS demands
 Tightly integrate these two parts
Alan Mislove, Ansley Post COMP 629
1.22.2004
Conclusion

IP does some things good, but not everything
 Good

for scarce-bandwidth situations
Wireless, undersea cables, satellite links
 Inappropriate


for real-time applications
Voice traffic, telephony
If we redesigned the Internet, not all routers would
be packet-switching
 Core
routers and real-time application data would be
circuit-switched
Alan Mislove, Ansley Post COMP 629
1.22.2004
Questions?

Mike O’Dell, former Senior VP, UUNet:
 “[to
have a voice-over-IP network service one has to]
create the most expensive data service to run an
application for which people are willing to pay less
money every day”
Alan Mislove, Ansley Post COMP 629
1.22.2004