Final Exam Review

-- Exam will focus primarily on the second half of the term.

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Address Spaces:

-- code, heap, stack, globals

Abstractions:
-- independence
-- protection & controlled sharing
-- simulating a larger memory
-- static vs. dynamic translation

static is limited because we need bounds checking on all pointer
derefences so we don't cross into another application's memory

Dynamic translation schemes:
-- uniprogramming
-- base and bounds
-- segmentation (multiple base and bounds). Problem is fragmentation
-- paging (segmentation with segments of constant size)
-- multi-level paging (page tables are tree of fixed depth). 
	* Allows for larger address space as we don't need to allocate all levels of the page table at startup
	* problem is indirection adds latency
-- Translation Lookup Buffer (multi-level paging optimization)
	* offsets problem of added indirection

Memory Replacement Policies:
-- Opt, LRU, Clock, etc.
-- deferring/avoiding work
-- page table bits
-- multi-process issues (thrashing, computing working set [???], etc)

Memory protection:
-- user-mode/kernel mode bit switch
-- has a pre-specified entry into kernel, only kernel can modify that handler entry.
-- kernel is paranoid about argument checking

Creating a Process (fork/exec)
-- copy-on-write
-- a unix shell
-- mmap/signal (not on the exam)

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File Systems:
-- device drivers provide readblock/writeblock abstractions.
-- translation/filesystem namespaces
	* How do we compute (offset, inode) -> block?
	* How do we compute path -> block/inode?
-- disk scheduling
-- file caching and fsync to force saving.
	* Memory-mapped files
-- durability issues
	* Careful ordering solves
	* atomic transactions
		~ Shadowing
		~ logging
-- distributed file systems
	* need caching to make performance reasonable
	* MESI protocol (like distrivbuted r/w locks)
-- Log Structured File System (LFS)

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Networking:

Sockets:
-- a bounded buffer
-- a port number (used for listen/accept on server and connect on client) (aka a mailbox)
-- [???] (TCP)
	* Reliable
	* ordered
	* bytestreams (data sent/recv independent of packet size)

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Distributed Systems:

-- Sharing via messages
-- synchronization via messages
-- Remote Procedure Call (RPC)
-- client/server paradigm
-- ordering of events
	* Lamport Clocks
-- Fault Tolerance
	* Stop Failures: primary backup fault tolerance [???]
	* Byzantine Failures: Byzantine Fault Tolerance (BFT) [???]
	* [Not on exam]: Paxos solves an intermediate level of failure.

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Security:

-- confidentiality
-- authenticity
-- freshness

Public-Key Cryptosystems
Private-Key CryptoSystems
Replay Attacks

General Security
-- authentication (verifying an identity)
-- authorization (permissions)