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Plan 9 from Bell Labs:
Real World Distributed Operating
System Case Study
Bryan Kinney
March 22, 2005
CPSC450/550 Distributed Operating Systems
Department of Physics, Computer Science and Engineering
Christopher Newport University
Plan 9
9Grid
Plan 9 Case Study
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Introduction
History
Goals
Definitions
Features
Using Plan 9
Applications
Significance
Summary
References
Plan 9: Introduction

Distributed System
 A distributed
system can be defined as a
system in which its components are
computers connected using a network that
communicate and coordinate their actions
only by passing messages [1].
Plan 9: Introduction
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Major Design Considerations of Distributed Systems [1]
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Heterogeneity
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Openness
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Provide a system that can deal with the failure of any one of its components.
Concurrency
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Provide a system in which the cost to support adding a user is consistent in terms of the
resources that must be added.
Failure handling
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
Provide adequate protection of shared resources and keep sensitive information safe
when transmitting messages.
Scalability
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Distributed systems should be extensible and provide published interfaces.
Security
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The system must be constructed from a variety of different networks, operating
systems, computer hardware and programming languages.
Provide safe concurrent requests to shared resources.
Transparency

Provide a single system image that allows the user to only be concerned with their
application and not aspects of the system such as networks topography and CPUs.
Plan 9: Introduction
Case Study
 How does Plan 9 compare to the definition
of a Distributed System?
 Does Plan 9 take into account the major
design considerations of:

Heterogeneity, Openness, Security, Scalability,
Failure handling, Concurrency, Transparency
Plan 9: History
Bell Labs began development in late
1980’s
 4 Releases
 Last Release was April of 2002

 Updated

June 2003
4th Edition available from Bell Labs site

http://plan9.bell-labs.com/plan9dist/index.html
Plan 9: History

Paradigm shift in mid 1980’s
 From:
Large centralized timeshared
computers
 To: Networks of smaller personal machines
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Typically UNIX ‘workstations’
Plan 9 wanted it both ways
 Central Administration
 Cost
effective
Plan 9: Goals
Build a time sharing system out of
workstations
 “Build a UNIX out of a lot of little systems,
not out of a lot of little UNIXs”

Plan 9: Goals

Specialization of hardware
 Different
computers for different tasks
 Small cheap machines in peoples offices

Terminals providing access to shared resources

 File
File servers, computing servers
Servers and CPU Servers in Server
Room
Plan 9: Goals
Centralized Time shared Systems
Plan 9 Distributed Operating System
Mainframe
High Speed
Network
Terminals
File Servers
CPU Servers
Centrally located multiprocessor machines with large
memories and high bandwidth point to point
interconnects.
Medium Speed Network
Personal Workstation Systems
Termina
l
Plan 9: Definitions

Plan 9:

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9Grid:


Plan 9 is the name of the Distributed Operating System designed and
implemented by researchers at Bell Lab in Murray Hill New Jersey. It is
available for download from the Plan 9 website [7].
9Grid is the name of a Plan 9 installation that provides Grid Style
Computing. More information can be found at the 9 Grid website [8].
8½:

The Plan 9 window system. It provides textual I/O and bitmap graphic
services to both local and remote client programs by offering a
multiplexed file service to those clients. It serves traditional UNIX files
like /dev/tty as well as more unusual ones that provide access to the
mouse and the raw screen. Bitmap graphics operations are provided by
serving a file called/dev/bitblt that interprets client messages to perform
raster operations [9].
Plan 9: Definitions
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Rc:
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9P Protocol:
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Rc is a command interpreter for Plan 9 that provides similar facilities to
UNIXs Bourne shell, with some small additions and less idiosyncratic
syntax [10].
The 9P protocol is the Plan 9 file system protocol. It is structured as a
set of transactions that send a request from a client to a (local or
remote) server and return the result [2].
IL Protocol:

IL is a custom implemented network protocol to transport the remote
procedure call messages 9P. It is a connection-based, lightweight
transport protocol that carries datagrams encapsulated by IP. IL
provides retransmission of lost messages and in-sequence delivery, but
has no flow control and no blind retransmission [6].
Plan 9: Definitions

Factotum:

Factotum is the central component of the security architecture.
Factotum securely holds a copy of the user’s keys and negotiates
authentication protocols, on behalf of the user, with secure services
around the network [5]
Plan 9: Features

Built upon 3 principles.
1.
Resources as files
Named and accessed like files in a hierarchical file system.
2.
Standard protocol
9P, for accessing these resources.
3.
Hierarchical file name space
The disjoint hierarchies provided by different services are joined
together into a single private hierarchical file name space.
Plan 9: Features
1.
Resources as files

All resources in Plan 9 look like file systems.
 File Oriented access
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

Hierarchical name tree
Accessible by name
Access contents by read and write calls
Plan 9: Features
2. 9P Protocol
 Standard Protocol
for accessing
resources
 Bell labs
implemented IL
Protocol for network
transport of 9P
messages
Plan 9: Features
3.
Hierarchical File namespace

Every resource in the system,
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

local or remote
User or process assembles a private view of the
system by constructing a file name space that
connects the resources.
Allows the user to access files that are local or
remote in the same manner. When writing a
program the user does not need to create code that
handles for cases in which the file is not local.
Those details are abstracted to the system.
Plan 9: Features

Security

Factotum is the central component of the security architecture.
Factotum securely holds a copy of the user’s keys and negotiates
authentication protocols, on behalf of the user, with secure services
around the network [5]
Plan 9: Features
Security

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Each box is a (typically)
separate machine;
Ellipse is a process.
FX are factotum processes
PX are the pieces and proxies
of a distributed program.
The authentication server is
one of several repositories for
users security information that
factotum processes consult as
required.
Secstore is a shared resource
for storing private information
such as keys; factotum
consults it for the user during
bootstrap
Plan 9: Features

Capabilities for Parallel Programming

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

Kernel provides a simple process model and a few
carefully designed system calls for synchronization
and sharing.
Parallel programming language called Alef supports
concurrent programming.
Although it is possible to write parallel programs in
C, Alef is the parallel language of choice.
Alef uses a system call called rendezvous to
provides a way for processes to synchronize.
Plan 9: Structure

Main Parts
 File
servers
 CPU servers
 Terminals (user
access points).

Plan 9 Distributed Operating System
Typically centrally
located file servers
and CPU servers
High Speed
Network
File Servers
CPU Servers
Centrally located multiprocessor machines with large
memories and high bandwidth point to point
interconnects.
Medium Speed Network
Termina
l
Plan 9: Using Plan 9
 Example:
 This
Echo Server
Code implements a typical
TCP listener.
 It announces itself
 listens for connections, and forks a
new process for each.
 The new process echoes data on
the connection until the remote
end closes it.
 The "*" in the symbolic name
means the announcement is valid
for any addresses bound to the
machine the program is run on.
Plan 9: Using Plan 9
 Example:
Echo Server
1. Announce()
2. Listen()
3. Accept()
|| Reject()
4. Process()….
5. Close()…
Plan 9: Using Plan 9

Example: Echo Server
1.
Announce()
Returns open file descriptor for
the ctl file of a connection and
fills dir with the path of the
protocol directory for the
announcement.
int announce(char *addr, char
*dir)
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Addr is the symbolic
name/address announced; if it
does not contain a service, the
announcement is for all
services not explicitly
announced.
Plan 9: Using Plan 9

Example: Echo Server
2.
Listen()
Listen returns an open file
descriptor for the ctl file and
fills ldir with the path of the
protocol directory for the
received connection.
It is passed dir from the
announcement.
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int listen(char *dir, char *ldir)
Plan 9: Using Plan 9
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Example: Echo Server
3.
Accept() and Reject()
Accept and reject are called
with the control file descriptor
and ldir returned by listen.
Some networks such as
Datakit accept a reason for a
rejection; networks such as IP
ignore the third argument.
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int accept(int ctl, char *ldir)
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int reject(int ctl, char *ldir, char
*reason)
Plan 9: Applications
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Developed in research environment
Continue research news way to work with Distributed Operating
Systems
9Grid

The Advanced Computing Cluster Research Lab, at Los Alamos
National Laboratory uses Plan 9 for a secure grid environment:

“… utilize the distributed features of the Plan 9 operating system to
create a tightly-coupled Grid environment in which running applications
can cross the boundaries of the local cluster or institution and utilize
resources around the globe or even further away. A distinguishing
feature of 9grid is its security model. Plan 9 is a far more secure system,
from the ground up, than any Unix system ever built. There is no need
for add-ons such as firewalls to make Plan 9 Grid-capable. As users
attach to nodes on the 9grid, their entire file system name space is
visible from all the nodes which they are using -- and invisible to anyone
else.”
Plan 9: Significance
Fulfills definition of Distributed System
 9P: Uses message passing to coordinate
actions
 Provides for the major design
considerations as outlined

 Heterogeneity,
Openness, Security,
Scalability, Failure handling, Concurrency,
Transparency
Plan 9: Summary

The Plan 9 Distributed Operating System is a
Distributed System which gives its users a single
system image of the system of networks and
hardware it manages. Plan 9 gives users the
tools for conventional programming and parallel
programming. Plan 9 is a distributed system
built from the ground up incorporating distributed
concepts and encouraging future research of
concepts developed through using distributed
computing environments.
Plan 9: References
1.
2.
3.
4.
5.
6.
Coulouris,George. Jean Dollimore, Tim Kindeberg, Distributed Systems
Concepts and Design. Pearson Education Limited, 2001
Pike, Rob. Dave Presotto, Sean Dorward, Bob Flandrena, Ken
Thompson, Howard Trickey, and Phil Winterbottom, Plan 9 from Bell
Labs,http://plan9.bell-labs.com/sys/doc/index.html
Presotto, Dave. Phil Winterbottom. The Organization of Networks in Plan
9, http://plan9.bell-labs.com/sys/doc/index.html
Pike, Rob. Dave Presotto, Sean Dorward, Bob Flandrena, Ken
Thompson, Howard Trickey, and Phil Winterbottom, The Use of
Namespaces in Plan 9,http://plan9.bell-labs.com/sys/doc/index.html
Cox, Russ. Eric Grosse, Rob Pike, Dave Presotto, Sean Quinlan.
Security in Plan 9. http://plan9.bell-labs.com/sys/doc/index.html
Presotto, Dave. Phil Winterbottom. The IL Protocol. http://plan9.belllabs.com/sys/doc/index.html
Plan 9: References
7.
8.
9.
10.
11.
12.
Plan 9 Website, http://plan9.bell-labs.com/plan9dist/index.html
9Grid Website, http://plan9.bell-labs.com/9grid/index.html
Pike, Rob. 8½, The Plan 9 Window System. http://plan9.belllabs.com/sys/doc/index.html
LDuff, Tom, Rc- The Plan 9 Shell. http://plan9.belllabs.com/sys/doc/index.html
Advanced Computing Cluster Research Lab, Los Alamos National
Laboratory. http://public.lanl.gov/cluster/projects/index.html
9Grid (LANL): http://www.9grid.net
Plan 9 from Bell Labs:
Real World Distributed Operating
System Case Study
Bryan Kinney
March 22, 2005
CPSC450/550 Distributed Operating Systems
Department of Physics, Computer Science and Engineering
Christopher Newport University
Plan 9
9Grid