1. AMOEBA
study of distributed system

2. what is Amoeba?
It is distributed operating system which collects a huge
variety of single machines connected over a network to
one ,huge computer.
It is developed at Vrije University in amsterdamby
Andrew S. Tannenbum.
AMOEBA system will connect the multiple AMOEBA
systems in different sites into single coherent system.
This goal is obtained by using objects and their
capabilities in uniform ways

3. History
Developed at the Vrije Universiteit Amsterdam,
Netherlands. Chief designer: Andrew S. Tanenbaum
Other developers were Frans Kaashock, Sape J.
Mullender, Robbert van Renesse, Leendert van
Doorn, Kees Verstoep and many, many more.
First proto release in 1983 (V1.0), last official
release 1996 (V5.3) Supports multiple architectures:
68k, i80386, SPARC

4. Design Goals
A. Transparency:
B. Distribution:
C. Parallelism:
D. Small kernel aprroach:
E. Performance:

5. System Architecture
It implements universal
distributed client-server
model.
Whole system need only
three functions to work:
1. Transaction call from
a client
2. thegetRequest
3. PutReply functions on
server side.

6. System Architecture
 It consists of four principle components:
1. File servers:
2. Workstations:
3. Pool processors:
4. Gateways:

7. Networking
Currently Amoeba has only
drivers for Ethernet,but other
network drivers are under
consideration.
Amoeba do not set upper
limit for no. of computers but
in some cases it is limited by
n/w bandwidth or topology.

8. Heterogeneity
Amoeba is reasonably portable and has run on five
architectures.
It is currently available on following architectures.
1. The motorola MC680x0 family
2. The intel 80386 family
3. Members of SPARC family
 Processor pool may contain processors more than
one type of architecture.
 Configurations supported:
Pool,specilazied server,workstation

9. AMOEBA KERNEL FEATURE
AMOEBA kernel has some major features over commonly
used other os kernels.
1. High performance server client communication:
 Remote procedure call:
 Interprocess procedure call:
2.Kernel administration:
 Remote rebooting of kernels:
 Remote status report:

10. AMOEBA’s object concept & capabilities
AMOEBA is organized as a
collection of objects:each with
some operations that process can
perform on it.
There are many object classes
like
files,directories,memorysegments,
processes etc.
 When an object is created, the
server returns a Capability.
 capability is used to address and
protect the object.

11. Process Management
A process is an object in Amoeba.
Information about the processes in Amoeba
are contained in capabilities and in a data
structure called a process descriptor.
Amoeba supports a simple thread model.
When a process starts up, it has at least one
thread. The number of threads is dynamic.
Three methods are provided for thread
synchronization:Mutexes,Semaphores ,Signals

12. Memory Management
Amoeba supplies a simple memory management based on segments.
Each process owns at least three segments:
1. Text/Code segment
2. Stack segment for the main thread/process
3. Data segment
Each further thread gets his own stack segment, and the process can
allocated arbitrary additional data segments.
All segments are page protected by the underlying MMU, the kernel
segments, too

13. Communication
All processes, the kernel too, communicate with a standardized RPC
(Remote procedure call) interface. There are only three functions to
reach this goal:
1. trans(req_header, req_buf, req_size, rep_header,rep_buf, rep_size)
do a transaction to another server
2. getreq(req_header,req_buf,req_siz)
get a client request
3. putrep(rep_header,rep_buf,rep_siz)
send a reply to the client

14. The Virtual Amoeba Machine
 The Virtual Amoeba
Machine Environment
consists of these main parts:
1. UThreads
2. AMUNIX
3. FLIPD
4. VAM

15. The Virtual Amoeba Machine
5. Amoeba
The native Amoeba kernel (called the VERTEX-Kernel), with these
features:
Clean and modern micro kernel design
Easy to implement device drivers
User space device driver support
Full network performance through direct FLIP network access
The kernel operates standalone, and needs no further configuration

16. General Requirements
The amoeba distributed operating system can run on many different
types and brands of computers.
It is intended that it should run on network with at least five
computers.
the main machine should be equipped with at least 64 MB RAM (128
MB recommended) and at least with 500MB disk space.
Currently, Fireball -Amoeba only supports Ethernet. In special only
the 10 MBit/s connectivity with RJ-45 or RG-58 connectors, and now
100 MBit/s Fast Ethernet, too.

17. Implementation
According to Tanenbaum (1990), AMOEBA system has been
implemented to five different CPU : 68010, NS 32016, 8088, VAX, PDP-
11.
Current configuration has 48 single board VME based computers
using 68020 and 68030 CPU and also 10 VAX CPU forming additional
processor pool.
Current research includes connecting AMOEBA at 5 locations in 3
countries. Using Wide Area Network facilities.

18. Security
 Amoeba has two level of protection:
1. Ports for protecting access to server
2. Capabilities for protecting access to individual objects.
 Hardware solution: A small interface box (F - box) are put between
each processor module and the network.
software solution: since ports for public servers are known to all
users it is easy for an intruder to impersonate a server just by doing a
get_rerequest on the server’s port.

19. Comparision of Amoeba and V
 Amoeba and V use the small kernel to provide the infrastructure of
the distributed system.
Amoeba and V are free-market model service, Service such as the
file system are in principle just an ordinary user process.
Amoeba and V use client-server and remote procedure call.
V does not have the processor pool, and there is no dynamic
processor allocation. Amoeba has a processor pool and does the
processor allocation.
Amoeba is more fault tolerance than V (Cheriton 1988), because V
was designed for interactive workstation, so if there are something
goes wrong, user can re-execute.

20. Field of Application
 Distributed measuring and data acquisition systems, for example
remote digital camera servers connected with an Ethernet network.
The native Amoeba kernel is very well suited for embedded systems.
Distributed control systems.
High performance parallel computing and other distributed numerical
computations.
Distributed file systems using raw disk access on the top of standard
operating systems.

21. Conclusion
 A distributed system potentially will be more reliable and low cost
than a time sharing system.
By placing the other service outside the kernel and keeping the
kernel as small as possible, the system is more flexible and reliable.
The client-server model with remote procedure call have proved that
using basic primitive communication the overhead of communication
can be reduced.
By using the object and capability model, Amoeba is more flexible
and more easily be used.
Amoeba is the only one Distributed Operating System which
implements Wide Area Network.

22. Thank you