any node is allowed to join

only members can communicate with each other

each node has a # of references to randomly selected other nodes

Resource managment

Facilities for interapplication communication

Security services

Accounting services

Masking of and recovery from failures

the SYSTEM decides to migrate

sometimes, it may best to expose disribution rather than trying to hide it

Cannot distinguish a slow computer from a failing (dead) one

Sometimes we needn't hide everything

Can never be sure that the server performed an operation before a crash

cost performance

Interface definition language (IDL)

what works on A, works on B (without modifications)

two implementations/components from different manufactureres co-exist

add new components or replace existing ones

Hardware

Platforms

Lanuage

Level of consistancy

Operations that allow for downloaded code

Quality of service

Level of secrecy

How policies are achieved

broadcasting (naming)

Share expensive resources between different domains

Trust?

the new domains

the distributed system

File-sharing

P2P telephony

peer-assisted

End users collaborate

improving capacity

hiding common latencies

distribution of work

replication