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1NOSSDAV 2008 KeynoteMay 29, 2008
Overlays can do more
… if not everythingJorg Liebeherr
University of [email protected]
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2
Acknowledgements
• Contributors: – Bhupinder Sethi, Tyler Beam, Burton Filstrup,
Mike Nahas, Dongwen Wang, Konrad Lorincz, Jean Ablutz, Haiyong Wang, Weisheng Si, Huafeng Lu, Josh Zaritsky, Jianping Wang, Guimin Zhang, Guangyu Dong, Greg Mattes, Zhi An, Shaoyi Chen, Wittawat Tantisiriroj,Majid Valipour, Jon Lei
• Funding: NSF, DOD, NSERC
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3
Internet-centric Networking
Things that are not needed:• Access to infrastructure • Allocation of global addresses• Resulting vulnerabilities
3GWiFi
Internet
128.100.128.100 64.2.125.201
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4
An Analogy
Internet todayappears like Mainframe computingof 1970s
Internet
3GWiFi
128.100.128.100 64.2.125.201
networking
Internet
Overlays
AllMany computing needs can be
met without mainframe computers
Smaller computers can replace
mainframes Internet
Overlay network
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Overlay-based networking
• Applications/devices self-organize as a network
• Application networks define their own address space
• Access infrastructure as needed
WiFi
Public IP network
ZigBee
100101
101 111 101
10010011 11110100
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Substrate (“underlay”) network
Overlay network
What is an overlay anyway?
• An overlay network is a virtual network of nodes and logical linksbuilt on top of an existing network
• A virtual link in the overlay corresponds to a path in the underlay
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Overlays Everywhere
• Overlays are a main architectural element for building complex networks
• 4 reasons to build overlay networks1. Virtualize network resources2. Deploy new network services3. Create sub-groups for information exchange 4. Interconnect substrate networks
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Application Layer Overlayslate 1990s
• Application-layer overlayon top of the Internet
• Made popular by – Application-layer multicast – Distributed lookup (DHT)
• Also: – Security– Intrusion detection– Replication– QoS
01
2
34
5
6
7query(7)
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Content distribution networks 1998
• AKAMAI overlay for content distribution:– 15,000 servers,
in 69 countries, within 1,000 networks.
Source: Wikipedia
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RON (resilient overlay network)2001
• Detect outages • Upon outage, relay data to a
peer node
ISP 1ISP 2
ISP 3
ISP 4
ParisLondon
Rome
failure
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MBone (1992), VPN Overlays (1994), 6Bone (2000)
• Deploy new services in IPv4 Internet– Multicast (MBone)– IPv6 (6Bone)– Security (VPN)
IP-in-IP
tunnel
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MBone (1992), VPN Overlays (1994), 6Bone (2000)
• Network-layer overlays– Principle: IP-in-IP encapsulation
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HAYSan Francisco
NCARNational Center for
Atmospheric Research
SDSCSan DiegoSupercomputer Center
HSJHouston
DNJDenver
Ameritech NAP DNGChicago
NCSANational Center forSupercomputingApplications
NORCleveland
PYMPerryman, MD
Sprint NAP
MFS NAP
PSCPittsburgh
SupercomputingCenter
RTOLos Angeles
A
ASTAtlanta
AWORNew York City
vBNS Backbone Network Map1997
CHTBoston
WAEWashington, DC
SEJSeattle
C*
A
A
J
C*J
Ascend GRF 400
Cisco 7507
Cisco 12008
Juniper M40
A
C
C
C
C
C
CC
C
C
C
C
C
C
C
C
C
C
C
C
FORE ASX-1000
NAP
DS-3
OC-3C
OC-12C
C*
J
Source: Internet archive, vbns.net, 2000
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14
LosAngeles
Chicago
Cleveland
Boston
SanFrancisco
Denver
Atlanta
WashingtonDC
NewYork City
Houston
Seattle PerrymaMD
vBNS: IP Topology1997
• Each vBNS node has an ATM switch and at least one IP router
• ATM switches build a PVP mesh between all nodes
• IP routers see full mesh topology
Source: Internet archive, vbns.net, 2000
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VLANs1998
• VLAN overlays separate broadcast domain from location of hosts
VLANswitches
VLAN 1 VLAN 2 VLAN 3
Router
Hubs
Router
LAN 1
LAN 2
LAN 3
Source: Cisco
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Heterogeneous Sensor Networksince 2005
• Interconnect remote wireless sensor networks• Extend overlay to sensor nets
Public IP network
WSN
WSN
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Mobile-ad hoc network
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Layered Overlay MANET
• Lower Layer: Mesh network is built by mesh radios
• Higher Layer: Overlay is created on top of the mesh network
A
C
F
E
B
D
A
C
F
E
B
D
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Integrated Overlay MANET
Overlay is responsible for creating and maintaining a mesh topology
C
F
E
B
D
A
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20
Disruptive Tolerant Networkssince 2000
• “Message Ferrying”• Multihop data path, but whole path may not exist at one
point in time.
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… and of course … The Internet
Ethernet
TokenRingLANEthernet
H1
R1 R2
R3 R4
H2
Network ofEthernetswitches
Point-to-point link Point-to-point link
• View at the data link layer layer:
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H1
R1 R2
R3 R4
H210.2.1.0/24
20.1.0.0/1610.1.2.0/24
10.1.0.0/24 10.3.0.0/16
20.2.1.0/28
… and of course … The Internet
• View at the IP layer:
IP
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???DTN
??MANET
?WSNs
IP Network
VLAN
?
Exchange G
roups
Interconnection
New
Service
Virtualization
Forwarding
Self-organization
ALMRONMBONE, VPN, 6BoneCDN (Akamai)IP over ATM
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Overlay Network Research
Past 10 years:– Mostly application-layer– Mostly single-substrate networks– Mostly structured topology– Distinct from mobile networks (MANET, WSN, DTN)
Future:– All layers– Multisubstrate networks– Structured topology if possible– Mobile overlays are integral
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Rest of Talk: How I came to think Overlays can do more
Topologies for large-scale overlays
Blurring the lines between overlays and MANETs
Overlay sockets: APIs for overlays
Using overlays for information management
Overlay network architecture
1997
2001
2004
2005
2007
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26
My point of Departure
• HyperCast (www.hypercast.org) is a set of protocols for large-scale self-organizing overlay networks
• ~100,000 lines of Java• Available on Sourceforge• Socket inspired APIs• Security, Monitor and control, …• Some applications
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HyperCast Overlay Networks
Applications self-organize to form a given overlay topologyData is forwarded along the edges of the overlay topology
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Local Area Experiments 2002
• Experimental Platform:Centurion cluster at UVA (cluster of 300 Linux PCs) – up to 100 PCs– Up to 100 members per PC
up to 10,000 overlay nodes
Switch 8
Switch 9
Switch 11
Switch 10
Switch 4
Switch 5
Switch 6
Switch 7
Switch 3
Internet
centurion149-167centurion183centurion253-255
centurion246centurion250centurion251
centurion249centurion252
centurion168-182centurion164-187
centurion188-211
centurion228-247centurion128-147
Gigabit Ethernet
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Experiment: Scalability
M+N members
Tim
e to
Com
plet
e (s
ec)
Topology: Delaunay TriangulationMeasurement: How long does it take to add M members to an overlay network of N
members ?
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Overlay Sockets
Substrate Network
Overlay socket
Application
Overlay socket
Application
ApplicationOverlay socket
Application
ApplicationOverlay socket
Application
(a) Overlay socket(b) Overlay Network
(Collection of overlay sockets)
Overlay Socket
Forwarding Engine
Overlay Socket API
Messages of overlay protocol
Node(Overlay Protocol)
Node Adapter
Applicationmessages
Application Program
Substrate Network
Socket Adapter
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Overlay Sockets
Substrate Network
Overlay socket
Application
Overlay socket
Application
ApplicationOverlay socket
Application
ApplicationOverlay socket
Application
(a) Overlay socket(b) Overlay Network
(Collection of overlay sockets)
Overlay Socket
Forwarding Engine
Overlay Socket API
Messages of overlay protocol
Node(Overlay Protocol)
Node Adapter
Applicationmessages
Application Program
Substrate Network
Socket Adapter
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Forwarding
• Data is forwarded along embedded trees
• Operations:– sendToChildren()– sendToParent()
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Forwarding
• Logical address (LA): overlay specific address of an overlay socket• Physical address (PA): address of the overlay socket in substrate network
PALA
164.2.41.3:4000:400111000
128.192.2.11:2400:240211111
myLA = 01101myPA = 128.100.2.6:9800:9801
128.100.2.6:9800 128.100.2.6:9801
SendTo (10011, Msg)
SendMsg (z, Msg)
z = getParent (10011)
Msg
To: 128.192.2.11:2402
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Writing Programs with Overlay Sockets
//Generate the configuration object OverlaySocketConfig ConfObj =
OverlaySocketConfig.createOLConfig("hypercast.xml");
//Create an overlay socket I_OverlaySocket socket=ConfObj.createOverlaySocket(null);
//Join an overlay socket.joinOverlay();
//Create a message OL_Message msg = socket.createMessage(byte[] data);
//Send the message to all members in overlay network socket.sendToAll(msg);
//Receive a message from the socket OL_Message msg = socket.receive();
//Extract the payload byte[] data = msg.getPayload();
//Generate the configuration object OverlaySocketConfig ConfObj =
OverlaySocketConfig.createOLConfig("hypercast.xml");
//Create an overlay socket I_OverlaySocket socket=ConfObj.createOverlaySocket(null);
//Join an overlay socket.joinOverlay();
//Create a message OL_Message msg = socket.createMessage(byte[] data);
//Send the message to all members in overlay network socket.sendToAll(msg);
//Receive a message from the socket OL_Message msg = socket.receive();
//Extract the payload byte[] data = msg.getPayload();
• Similarities to Berkeley Socket API• Programs are independent of overlay topology and substrate network• Arbitrary number of overlay sockets per applicaiton
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Experiment: Throughput of Multicasting
Number of Members N
Bandwidth bounds
Measuredvalues
Ave
rage
thro
ughp
ut
(Mbp
s)
100 MB bulk transfer for N=2-100 members (1 node per PC) 10 MB bulk transfer for N=20-1000 members (10 nodes per PC)
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Hypercast Application: Video-streaming in ad-hoc network
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Snapshot
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Wireless Ad-hoc Measurements(2005)
• HP iPAQ 5555 PDA (x 8)– 400MHz Intel XScale CPU, 128MB– Jeode JVM– WiFi 802.11b
• Toshiba M200 Tablet PC (used as monitor)– 1.5GHz Intel Centrino CPU, 512MB– WiFi 802.11g
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Performance of Overlay in Ad hoc network
Single hop, point-to-point:• One sender, one receiver• Indoor, approx. 30ft distance• TCP is used as underlay protocol• 10,000 messages (@512 bytes) • Short ACK (32 bytes) is sent for each
message to measure RTT• Overlay socket is compared to plain
TCP socketwithout overlay (plain TCP)
100
200
300
400
500
600
700
800
900
1000
0 2000 4000 6000 8000 10000
Thr
ough
put (
kbps
)
Sequence Number
with overlay
0
with overlay
250
500
750
1000
1250
1500
0 2000 4000 6000 8000 10000
Rou
nd T
rip
Tim
e (m
s)
Sequence Number
without overlay (plain TCP) 0
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Performance of Overlay in Ad hoc network
Multi-hop:
• Six iPAQ PDAs in a line topology• Distance between PDAs is 30, 60, 90 ft• Outdoor measurement (taken over several
days) • 10,000 messages (@ 512 byte) • TCP adapter• Fixed topology
0
100
200
300
400
500
600
700
54321A
vera
ge T
hrou
ghpu
t (kb
ps)
Hop Count
30 feet60 feet90 feet
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AlertVideo
Information Management with Overlay Networks
Concept: • Each resource or user can be a member of arbitrarily many peer networks• Access to information is provided through dynamically created overlay
networks
File
message
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HyperCast Application: Location Aware Messaging System(2003)
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HELP
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HyperCast Application: Area Protection(U. Virginia, 2004-05)
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MobileCommander
`
Base Station
Early Warning Zone
Area Denial Zone 2
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Area Denial Zone 1
Zone Control Overlay
Early WarningOverlay
Area Denial Overlay
Mobile CommOverlay
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30 years ago ….
H1
R1 R2
R3 R4
H210.2.1.0/24
20.1.0.0/1610.1.2.0/24
10.1.0.0/24 10.3.0.0/16
20.2.1.0/28
• The Internet emerges as an overlay network:– Collection of networks form a single internetwork– New service is end-to-end packet delivery
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Toward an Overlay Network Architecture
Objective:Create a network architecture entirely based on the concept of self-organizing overlay networks
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Sensors/Motes
Today or soon …
• Connection to a single infrastructure/address space not feasible or desirable• Objective: Connect applications via self-organizing overlays• Each overlay creates its own address space
Mobile Devices
Public IP network
New Network Layers
Private IP networks
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Toward an Overlay Network Architecture
Objective:Create a network architecture entirely based on the concept of self-organizing overlay networks
Challenges:• Build overlay networks across any mix of layer-1, layer-2,
layer-3, and application layer networks• Support a virtually unlimited number of overlay networks• Build very large overlay networks very quickly
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Performance of Overlay-over-Ethernet(2007)
Single Hop, Multicast:• Single overlay• 1 sender, 1-4 receivers• Shared Ethernet (GigE) LAN • Single-substrate:
– UDP– TCP – Ethernet (no IP)
• 8,192 messages (@ 1200 bytes)• Max. transmission rate
Receiver
Receiver Receiver
Receiver Receiver
Receiver
Sender
0
50
100
150
200
250
avg.
thro
ughp
ut (M
bps)
1 2 3 4# receivers
TCPUDPEthernet
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Multi-substrate networks
WiFi
GigE
NAT IPv6IPv4
ZigBee Application-layerOverlay
ZigBeePublic IP network
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Problem to solve: Multiple substrate networks
Overlay Socket
Forwarding Engine Message Store
Overlay Socket Interface
Application Receive Buffer
Overlay Node
Node Adapter Socket Adapter
Application Program
Substrate
Substrate 2
Substrate 3
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The strawman
if 1 if 2 if 3 interfaces
IA 1 IA 2 IA 3 Interface addresses(e.g., “128.100.243.2/3444”)
• Solution: – One “logical address” per socket– One “interface address” per substrate network – Each adapter has one interface for each substrate.
LA Logical addresses(e.g., “10110001”)
adapter
node
Note:IP : one IP address per layer-2 interfaceHere: same logical address for all interfaces
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Multi-substrate overlay socket
Stat
istic
s In
terf
ace
Substrate
Substrate 2
Substrate 3
Adapter has one interface for each substrate.
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Issues in multi-substrate overlays
1. Cross-substrate advertising2. Need for and design of “relays”
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Cross-substrate advertising
Example 1:• A and B prefer Substrate 1, but does not have address of A • Use Substrate 2 for rendezvous, and exchange address information about
Substrate 1
BSubstrate 1(Internet)A
Substrate 2
Addr_A
HelloHello (+ Addr_A)
Hello
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Cross-substrate advertising
Example 2:• C joins overlay via Substrate 3 with B as neighbor• C prefers A as neighbor in the overlay • C detects that it can talk to A via Substrate 2
B
C
Substrate 3Substrate 1
A
Substrate 2(no broadcast)
Addr_A
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Cross-substrate advertising- Outgoing -
myLA = 50,102
Source: 50,102
Adr_1 Adr_2 Adr_3
Adr_1
Adr_2
Adr_3
List of substrate addresses
Source: 50,102 Adr_1 Adr_2 Adr_3
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Cross-substrate advertising- Incoming -
Substrate addressesLA
Adr_1, Adr_2, Adr_350,102
Source: 50,102
Source: 50,102 Adr_1 Adr_2 Adr_3
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Cross-substrate advertising (CSA)- Features -
• Independent of overlay protocol (topology)• CSA component need not interpret addresses
• CSA messages are:– standalone, or – encapsulate protocol message
• CSA messages can be sent by:– Explicit request -– Broadcast – Gossiping
• Consider “preferences”– E.g., create topology over WiFi, data over GigE
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Address entries: Format
Source: 50,102 Adr_1 Adr_2 Adr_3
<1000,overlay_DT,(100,100)>
OverlayInterfaceoverlay id= 1000protocol = DT protocollogical address =(100,100)
<ethernet ,multiplexing_ethernet, FF:FA:34:09:41/1234>
MACEthernetFF:FA:34:09:41Mux number=1234
<private1,udp,192.168.0.10:8001>Private IP: private1192.168.0.10UDPMulticast, port 8001,Multicast address:24.228.19.78:9999
<public,tcp,128.100.100.128:8001>Public Internet 128.100.100.128TCPUnicast, port 8001
Address list entrySubstrate address
<address realm, protocol, length, address>
< hash, length, address>
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Demo: Cross-substrate advertisement
• Two substrates: • <udp1>• <udp2>
• 3 groups of overlay sockets:– Group 1 and 2:
one interface to different substrates
– Group 3: two interfaces
• One overlay network: DT protocol
Substrate 2
Substrate 1
Group 1
Group 2
Group 3
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Relays
• Relays provide connectivity between substrate networks– Can serve as rendezvous points across substrates– Help with getting data across substrates
Substrate
Substrate
Substrate
Substrate
Substrate
Substrate
R
R
R
R R
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Relays
• Questions:– Are relays part of the overlay network? Should they be
transparent?– How do nodes find relay and how do relays find each
other?
Requirements:• Support many (unlimited) overlay networks• Virtualization of the data plane:
– Instantiate a separate data plane for each overlay– Create forwarding state upon request
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Next: Overlay software on FPGA
• Current project (2008):– Overlay router (“relay”) – Platform:
NetFPGA from Stanford U.– Xilinx Virtex-II Pro 50– 4 GigE ports
• Native support of (HyperCast) overlay protocols
• Arbitrary number of overlays:– Each overlay is a separate
data plane
Source: www.netfpga.org
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Summary
• 1960s-1990s: Overlays are key architectural element for building networks… but rarely self-organizing
• Last 10 years: Many new insights on self-organizing application-specific overlays
… but mostly single substrate (Internet)… mostly application-layer
• Next: New network architecture based on principles of self-organizing overlays:
… each networked application builds network with own address space … arbitrary substrates… less dependent on infrastructures… less need for management… mobilility not an issue
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When are we done ?
Putting overlays
on top of overlays
on top of overlays
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Some Guidance from Monty Python’s Flying Circus
There are many things, and I cannot emphasize this too strongly, not on top of other things. …For, we must never forget that if there was not one thing that was not on top of another thing our society would be nothing more than a meaningless body of people that had gathered together for no good purpose.
“Society for Putting Things on Top of Other Things” (ca. 1970)