CS 6250 Exam 2 Latest Update - Actual

CS 6250 Exam 2 Latest Update - Actual Exam 300 Questions and 100% Verified Correct Answers Guaranteed A+

• states of playout buffer. Pattern? - CORRECT ANSWER: 1. filling state - buffer is empty, must be filled

ASAP

• steady state - buffer is full, wait til it is lower than a threshold. send request for more content

on-off patterns

• categories of multimedia applications - CORRECT ANSWER: 1. stored audio and video (youtube)

• conversational voice and video over IP (skype_

• streaming live audio/video (grad ceremony)

• functions of signaling protocols? - CORRECT ANSWER: 1. user location - establish location
• session establishment - handle endpoints accepting or rejecting call
• session negotiation - endpoints sync with each other on set of properties for the session
• call participation management - handle endpoints joining or leaving

• goals of good Quality of experience/ bitrate adaptation - CORRECT ANSWER: 1. low rebuffering
• high video quality
• low quality variations
• low startup latency

Are blocklists at 2 different GFW locations different? Why? - CORRECT ANSWER: No, because of GFW manager 1 / 4

(10)

Are distributed controllers fault tolerant? - CORRECT ANSWER: Yes

(8)

Are processes clustered or separated with load balancing? Why? - CORRECT ANSWER: clustered - collectively send DNS responses (10)

Are SDNs built on open, standard interfaces? Why? - CORRECT ANSWER: Yes. configuration and communication compatibility can be among different apps and devices (8)

Are southbound APIs a barrier for acceptance of SDN technology? What will fix this? - CORRECT ANSWER: Yes. API proposals that standardize these southbound APIs, like Openflow, address this (8)

blocking with resets vs. immediate reset of connections - CORRECT ANSWER: - content based vs. identity (source) based (10)

can upstream provider/IXP help with blackholing? How? - CORRECT ANSWER: Upstream AS drops traffic towards victim

provider advertises more specific prefix, and modifies next hop address

adds blackholing community attribute

traffic goes to null interface (and is dropped)

(9) 2 / 4

Compare bitrate for video, photo, audio - CORRECT ANSWER: 1. video

• photo

• audio (marginally lower than photo)

Did active network do anything for performance? Security? - CORRECT ANSWER: No (7)

Did openflow prevent small players from being competitve? Why - CORRECT ANSWER: No, became more competitive b/c they could just focus on writing control programs instead of proprietary switches (7)

Difference between DNS injection and TCP RSTS - CORRECT ANSWER: TCP RSTS allow blocking of individual connections, DNS injections block entire domain name (10)

Difference between rogue and legit networks? - CORRECT ANSWER: - longevity of malicious behavior

• legit networks can remove them much more quickly

(9)

disadvantage of http get for video? - CORRECT ANSWER: 1. download is a waste if users leave

• buffering downloaded but unplayed data

Do distributed controllers have weak consistency of semantics? - CORRECT ANSWER: Yes (8)

Do SDNS have a physically centralized control plane? - CORRECT ANSWER: No, physically DISTRIBUTED 3 / 4

(8)

Do SDNs have logically distributed controller? - CORRECT ANSWER: No, logically CENTRALIZED (8)

Does FIRE observe networks w/ malicious IP addresses that have been up for a short period of time? -

CORRECT ANSWER: No because legit networks can remove content quicker

(9)

Does majority think GFW nodes present only at edge IPs? - CORRECT ANSWER: Yes - only at edge (10)

Explain 3 types of AS-path announcement hijacking - CORRECT ANSWER: - Type-0 - announce prefix not owned by itself

• Type-N - announce illegitimate path to prefix it doesn't own

• Type-U does not modify AS-PATH but changes prefix

(9)

Explain 3 types of classification by affected prefix: - CORRECT ANSWER: - exact prefix hijacking: announce path for same prefix

• sub-prefix hijacking - announce traffic for more specific, sub prefix

• squatting - advertise address that belongs to a different AS

(9)

Flowspec vs. ACL filters? - CORRECT ANSWER: Flowspec uses control plane

easier to add rules to routers

• / 4