President Obama was born in which U'S' state - PowerPoint PPT Presentation

About This Presentation

Title:

President Obama was born in which U'S' state

Description:

... put up the group , and ask groups to vote using the group clickers only ... connections between two nodes on the same physical LAN with one node connected ... – PowerPoint PPT presentation

Number of Views:35

Avg rating:3.0/5.0

Slides: 32

Provided by: scie205

Category:

more less

Transcript and Presenter's Notes

Title: President Obama was born in which U'S' state

1
President Obama was born in which U.S. state

Illinois
Texas
New York
Hawaii
Trick Question Washington DC
Kenya

2
Hawaii (4) is right

He was Senator for Illinois
George W Bush was Texas
His father was from Kenya, but had he been born
there he would probably not have been eligible
(article 2.1.5 of U.S. constitution)
DC is indeed not a state, but counts as U.S. for
the purpose

3
That was the warmup

Now to check clickers against groups
IF your group name is shown, please press the
associated number on each individual clicker AND
the group clicker
ELSE wait for next slide(s)

4
Please select a TeamIf youre not here, wait.

Team A
Team B
Team C
Team D
Team E

5
Please select a Team If youre not here, wait.

Team F
Team G
Team H
Team I
Team J

6
Please select a Team If youre not here, you
should have been done already

Team K
Team L
Team M
Team N

7
Now for your questions

Im going to show the individual slide please
answer as individuals.
Then Ill ask you to start conferring. Part way
through this, Ill show the individual answers.
Then Ill put up the group slide, and ask groups
to vote using the group clickers only
A group should vote on its own question

8
I Which of the following scenarios would benefit
most from disabling TCP slow start?

Many TCP connections between two nodes on the
same physical LAN with one node connected via a
physical link consisting of a wireless ethernet
card.
Many TCP connections between two nodes connected
over a WAN. Again one node is connected via a
physical link consisting of a wireless ethernet
card.
Many TCP connections between two nodes on the
same physical LAN
Using VOIP over a LAN.
When transferring a large file over the internet.

9
G Which of the following scenarios would benefit
most from disabling TCP slow start?

Many TCP connections between two nodes on the
same physical LAN with one node connected via a
physical link consisting of a wireless ethernet
card.
Many TCP connections between two nodes connected
over a WAN. Again one node is connected via a
physical link consisting of a wireless ethernet
card.
Many TCP connections between two nodes on the
same physical LAN
Using VOIP over a LAN.
When transferring a large file over the internet.

10
Justification of answers

We think answer 1 is the scenario that would
benefit most from having TCP slow start
disabled. Therefore answer 1 is the "correct"
answer.
For 1,2,3 - The fact that 'many' TCP
connections are made makes little difference. Any
overhead (CPU/memory) required for many slow
start algorithms running simultaneously is
negligible.
Slow start is about protecting networks

11
I With regard to Silly Window Syndrome (SWS),
Nagles Algorithm

Solves the problem of SWS.
Only solves certain cases of SWS.
Solves SWS when a receiving TCP is serving an
application that consumes data too slowly.
Is appropriate when Clarks solution or Delayed
Ack wont work

12
G With regard to Silly Window Syndrome (SWS),
Nagles Algorithm

Solves the problem of SWS.
Only solves certain cases of SWS.
Solves SWS when a receiving TCP is serving an
application that consumes data too slowly.
Is appropriate when Clarks solution or Delayed A
wont work.

13
Answers

The answer 2!
False It only solves half the problem it solves
it on the sender side, by preventing the sender
from sending tinygrams, but it doesnt stop the
receiver from advertising tiny windows.
True It doesnt solve the problem of the
application on the receiving side reading data
too slowly.
False Clarks solution and delayed
acknowledgements deal with this side of the
problem.
True, but a worse answer than 2 Clarks solution
and Delayed Acknowledgements are actually solving
the other half of the problem, and both
techniques are required to prevent SWS from
occuring.

14
I Which of these is the most important factor in
the reliability of a secondary DNS server?

Being located in a different country to the
primary
The primary server is polled for changes
frequently
Running on the same hardware as the primary
machine
Being connected to the net via different routes
to the primary and other secondary servers

15
G Which of these is the most important factor in
the reliability of a secondary DNS server?

Being located in a different country to the
primary
The primary server is polled for changes
frequently
Running on the same hardware as the primary
machine
Being connected to the net via different routes
to the primary and other secondary servers

16
Answer

Correct RFC 2182 describes best current
practice as having at least one secondary server
on a different international backbone to the
primary server.
Correct Polling frequently (normally around
every 3 hours) ensures data is accurate and up to
date.
Wrong
Correct This is (arguably) the best answer, and
can be implied by 1, but may not be. Two
countries can use the same pipe to the rest of
the world, having a primary in one and a
secondary in the other wouldnt be ideal.

17
Protocol-Independent MulticastHow to do
multicast routing

PIM is actually a variety of protocols,
PIM Sparse Mode (PIM-SM) explicitly builds
unidirectional shared trees rooted at a
rendezvous point (RP) per group, and optionally
creates shortest-path trees per source. PIM-SM
generally scales fairly well for wide-area usage.
See the PIM Internet Standard RFC 4601
PIM Dense Mode (PIM-DM) uses dense multicast
routing. It implicitly builds shortest-path trees
by flooding multicast traffic domain wide, and
then pruning back branches of the tree where no
receivers are present. PIM-DM generally has poor
scaling properties.1
Bidirectional PIM explicitly builds shared
bi-directional trees. It never builds a shortest
path tree, so may have longer end-to-end delays
than PIM-SM, but scales well because it needs no
source-specific state. See Bidirectional PIM
Internet Standard RFC 5015
PIM source-specific multicast (PIM-SSM) builds
trees that are rooted in just one source,
offering a more secure and scalable model for a
limited amount of applications (mostly
broadcasting of content).

18
I In what way is Internet Group Management
Protocol inefficient?

IGMP has no guarantee that a report is delivered
IGMP is not a transport protocol, but instead
instantiates PIM connections
Multicast use in WANs causes lots of problems
It is in fact efficient

19
G In what way is Internet Group Management
Protocol inefficient?

IGMP has no guarantee that a report is delivered
IGMP is not a transport protocol, but instead
instantiates PIM connections
Multicast use in WANs causes lots of problems
It is in fact efficient

20
Answer Slide

All answers are true to an extent, but (3) is
best.
1) Although can be a problem, is generally
solved due to answer 4).
2) It creates a group before it implements
Protocol Independent Multicast. It would be more
efficient to use this all the time.
3) Not fully solved so problems may arise when
used.
4) Has efficiency methods For 1) IGMP sends
membership query messages repeatedly until an
acknowledgment is received. Also has scheduling
so not to send the same report twice.

21
DNS server records (SRV)

MX records are specific to SMTP, and assume you
know to use TCP port 25
You (or your browser) have to guess to stick www
on the front of a web address, and use TCP port
80
Instead, why not look up a generic service
record, e.g. _smtp._tcp.bath.ac.uk

22
I MX Records serve a similar purpose for SMTP as
SRV Records serve for other protocols.Which of
the following statements do you most agree with?

It is necessary to have both MX and SRV Records
MX Records should be phased out and replaced by
the more generic SRV Records
MX Records should remain because it would be too
difficult to replace as their use in email is so
entrenched them
SMTP itself is a flawed protocol and should be
replaced altogether

23
G MX Records serve a similar purpose for SMTP as
SRV Records serve for other protocols.Which of
the following statements do you most agree with?

It is necessary to have both MX and SRV Records
MX Records should be phased out and replaced by
the more generic SRV Records
MX Records should remain because it would be too
difficult to replace them their use in email is
so entrenched
SMTP itself is a flawed protocol and should be
replaced altogether

24
Answers

1. False. The data stored in SRV Records is a
superset of the data in MX Records, thus it is
possible for SRV Records to serve the same
purpose. 2. Arguably True. For the same reasons
as 3, its debatable whether the impact on old
software would cause a major problem. Otherwise,
as mentioned, SMTP would be trivial to
change.3. Arguably True. It would be trivial to
change the SMTP protocol to use SRV Records, but
old software would still be looking for MX
Records.
4. Debatable. This answer is meant to be thought
provoking. Why is SMTP one of the few protocols
that requires its own record?
SRV has Priority, Weight, Port and Target. MX
has Priority and Target

25
Networking

A few questions on the course
A few questions about the course, and this
teaching methodology

26
I Good fun, something different and its very
good to be interactive since we do not get much
class participation, except if we want to ask
questions