I Lab 1
The following is a working exploit for exercise 2 in lab 1:
reqpath = 0xbfffedf8
retaddr = ebp + 4
req = ( GET / +
x * (retaddr - reqpath - (len(shellcode)+8) +
6.824 2006 Lecture 14: Paxos
From Paxos Made Simple, by Leslie Lamport, 2001
2-phase commit is good if different nodes are doing different things
but in general you have to wait for all sites and TC to be up
you have to know if each site vote
I Part One
1. [10 points]:
Suppose youre running Mach 3.0 on a MIPS R3000. Youre getting tired of
how slow your 15-year-old CPU is. You hear that Anderson et al., authors of the Interaction paper, have started a company that sells a MIPS R3000-compatible
6.824 2006 Lecture 13: Two-Phase Commit
General topic: coordinating servers in a distributed system.
Prev lectures: agree on order of updates to replicas, no failures.
Today: general-purpose agreement on some action, w/ failures.
Next few lectures: agree
Non-uniform doping/excitation: Summary
What we have so far:
Five things we care about (i.e. want to know):
Hole and electron concentrations:
Hole and electron currents:
p(x,t) and n(x,t)
J hx (x,t) and J ex (x,t)
E x (x,t)
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Department of Electrical Engineering and Computer Science
6.012 MICROELECTRONIC DEVICES AND CIRCUITS
Answers to Exam 1 - Spring 2006
Problem 1: Graded by Prof. Hoyt
Na = B concentration = 2 x 1016 cm-3.
Non-uniform doping in thermal equilibrium
Reviewing from Lecture 3:
In a non-uniformly doped sample in TE we have: gL(x,t) = 0,
Je(x) = 0, Jh(x) = 0, and / dt = 0. Also: n(x) = no(x) and p(x) = po(x).
Applying these conditions to the two current density
Comments/Rules and expectations
Recitations: They re-enforce lecture.
They present new material.
They are very important.
They begin Monday, September 14.
Assignments will be posted on website.
Homework: Very important for learning; do it!
6.824 2006 Lecture 12: Vector Timestamps
Topic: Vector Timestamps / Version Vectors
Usually used for file synchronizers
Treadmarks use them also
so far we've talked about enforcing some order of operations
either implicitly because they go thru file serve
Extrinsic Silicon, cont.: solutions in Cases I and II
Case I - n-type: Nd > Na:, (Nd - Na) > ni
Define the net donor concentration, ND:
N D " (N d # N a )
n o " N D , po = n i2 (T) /n o " n i2 (T) /N D
n o > n i > po !
In Case I the c
Compile-Time Reasoning About
Run-Time Values of Variables or Expressions
At Different Program Points
Which assignment statements produced value of
variable at this point?
Which variables contain values that are no longer
6.824 2006 Lecture 15: Viewstamped Replication
From "Viewstamped Replication: A New Primary Copy Method to Support
Highly-Available Distributed Systems," Oki and Liskov, PODC 1988.
Recall overall topic: replicated fault-tolerant services
E.g. lock server