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CS 6250 TEST 1/32 QUESTIONS AND ANSWERS
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- CS 6250 TEST 1/32 QUESTIONS AND ANSWERS
CS 6250 TEST 1/32 QUESTIONS AND ANSWERS
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CS 6250 TEST 1/32 QUESTIONS ANDANSWERS
Standardized traffic routing between networks (all use IP), opens the way for
different protocols to be used at higher/lower levels.
IP responsible for moving traffic between networks (level 3), each network
may network may use tech they choose at lvl 1 and 2 to move traffic within
their net. Data can still traverse internet because IP glues different networks
together.
Higher layers (transport/application) operate strictly end-to-end. Since IP
works in the core of network, any end-to-end services may be built on top of
it. - -How does the "narrow waist" allow a large variety of different protocols
to be used on the Internet?
-Goals: Connect disparate individual (layer 2) networks by inter-networking
them with IP (layer 3).
ARP translates between different addressing schemes of IP (L3) and Ethernet
(L2).
E-2-E communication through IP (L3) because src/dest may not be on same
local (L2) network.
Internet comm dependent on local L2 network being able to deliver within
that network using MAC. Thus ARP fills the need to find MAC address of a
machine using the IP (L3) address.
Keep in mind not all L2 networks use MAC -- narrow waist dictates all
networks use IP at L3, but L2 may have other addressing.
ARP allows for IP→MAC mapping discovery dynamically, on an as-needed
basis. Thus there is no need for a machine's IP→MAC mappings to be
proactively reported to other hosts on the network. - -Discuss how the
design principles of the Internet are manifest in the ARP protocol.
Also discuss how the absence of some points from the design principles (e.g.,
security and mobility) has influenced ARP.
-Guaranteed bandwidth -> sufficient throughput available for video,
throughput won't be effected by other users'/applications' traffic on the
network (dedicated circuit for communication)
, Circuit switched can't prevent all packet loss, but the ability to reserve
sufficient resources for video traffic can eliminate a major source of packet
loss.
Certain video streaming applications (VOIP / video conference) may benefit
from the upper bounds on latency that circuit switched networks can
provide. - -What are the advantages of using circuit-switched networks
instead of
packet-switched networks (like the Internet) for streaming video?
-HTTP proxies divert web requests from their stated dest (web server) to the
proxy, which is likely closer to the requestor (client/browser) and can
respond with less latency, providing the same content.
Desirable for performance gains, however violates E2E argument. Remote
host you end up talking to is not the one you stated you wanted to talk to.
Can use encryption for proxy-client, however, E2E encryption between
client/original web server not possible.
Original web server cannot identify itself to client while proxy acts as
intermediary. Proxy could identify itself, but additional mechanisms would be
needed to verify proxy is authorized to act upon web server. - -In what way
are caching HTTP proxies a violation of the end-to-end argument? Also, what
are the consequences of this?
-Encryption could be performed every step, however intermediate routers
will see the traffic, as it is sent encrypted over one link to the router,
decrypted, then re-encrypted for the next link.
Must trust router, however this is not advisable due to distributed mgmt of
internet. Neither sender or receiver can guarantee which routers (and
therefore other organizations) their traffic will or will not traverse.
Man in the middle attacks possible by posing as a legitimate router or other
end. Cleartext visible of all supposedly-encrypted traffic. Possible to hack a
legitimate router and steal cleartext.
If one end does not identify themselves, you may know you have a secure
connection but do not know if you are talking to who you want to. - -Why is
it important for encryption to be end-to-end?
In other words, what are the consequences if we perform encryption, but not
in an end-to-end manner?
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