3700 Networking MIDTERM

TCP service

- reliable transport between sending and receiving process - flow control: sender won't overwhelm receiver - congestion control: throttle sender when network overloaded - does not provide: timing, minimum throughput guarantee, security - connection-oriented: setup required between client and server processes

Suppose there are two links between a source and a destination. The first link has transmission rate 100 Mbps and the second link has transmission rate 10 Mbps. Assuming that the only traffic in the network comes from the source, what is the throughput for a large file transfer.

10 Mbps

Suppose a client sends an HTTP request message with the If-modified-since: header. Suppose the object in a server has not changed since the last time a client retrieved the object. Then the server will send a response message with the status code: - 304 Not modified - 200 Ok - 404 Not found - none of them

304 not modified

Presentation Layer

Allows hosts and applications to use a common language; performs data formatting, encryption, and compression.

OSI Model Layers

Application, Presentation, Session, Transport, Network, Data Link, Physical

A mobile device such as a tablet CANNOT be treated as an end system in the context of networking

False

A user requests a Web page that consists of some text and three images. For this page, the client will send one request message and receive four response messages.

False

ADSL bandwidth is shared

False

Before sending a packet into a datagram network, the source must determine all of the links that packet will traverse between source and destination

False

DNS is organized as a centralized structure in order to provide reliable services

False

DNS servers are organized in a hierarchical structure, and the TLD servers are in the first level

False

Ethernet is a popular residential access technology

False

Flash can aid the http protocol to keep 'state' in web communications

False

HTTP protocol is a "stateful" protocol, which means servers will maintain information about past client requests

False

In BitTorrent, a peer's instantaneous download rate can never exceed its instantaneous upload rate

False

In P2P architecture, there should be a stable always-on server to provide reliable services to network users

False

In P2P file distribution, an entire file should never be divided into chunks in order to provide file integrity

False

In computer networking, data cannot be sent over DSL phone line

False

In computer networking, switches and routers always perform the same functions

False

In computer networking, the transport layer is responsible for the logical communication between hosts

False

In computer networks routers are mainly used to control sending and receiving of messages

False

In computer networks, a packet will never be dropped even the buffer on a router is full

False

Mobile Networks are more flexible than home network, therefore routers should not be used in mobile networks

False

On the sender side of network communications, the data will go through the network layer first and then go through the transport layer

False

The Date: header in the HTTP response message indicates when the object in the response was last modified.

False

With non-persistent connections between browser and origin server, it is possible for a single TCP segment to carry two distinct HTTP request messages

False

What is the data unit sent/received over the Link layer in OSI model? - Message - Datagram - Segment - Frame

Frame

HFC

Hybrid Fiber Coax homes share access network to cable headend unlike DSL which has dedicated access

queuing and loss

If arrival rate (in bits) to link exceeds transmission rate of link for a period of time: packets will queue, wait to be transmitted on link packets can be dropped (lost) if memory (buffer) fills up

Inter-process Communication

Information sharing between processes to speed up computation, allow modularity, convenience

Which statement is True about the traceroute command? - It traces the routing path of a packet from source to destination - it traces the forwarding path of a packet from source to destination - It traces the storing procedure of a packet from source to destination

It traces the routing path of a packet from source to destination

Which Option Is Not a Networking Protocol? - Pop3 - MBP - TCP - FTP

MBP

P2P architecture

No always-on server; arbitrary end-systems directly communicate; peers request service from other peers, provide service in return to other peers; peers are intermittently connected and change IP addresses

Four sources of packet delay

Nodal Processing, Queueing Delay, Transmission Delay, Propagation Delay

Which type of data cannot be sent over cable network - Video - Text - Audio - None

None

Which device is typically used to connect an Ethernet to an internet service provider (ISP) - Switch - End System - Data Server - Router

Router

Which device is typically used to connect multiple different networks? - switch - DSL - Fiber - Router

Router

Which protocol is used to control data sending and receiving between mail servers in E-mail communications? - FTP - SMTP - POP3 - IMAP

SMTP

Which option is NOT the source of a packet delay in computer networking? - Propogation Delay - Segment delay - Transmission delay - Nodal processing

Segment delay

Bandwidth is actually a metric to describe the capacity of a computer network

True

DNS lookups often involve a combination of recursive and iterative queries

True

Domain name system aims to perform hostname to IP address translation

True

If a POP3 client does not send the `dele` command, copies of the messages that the client has retrieved remain in the mail server

True

In networking can routers and switches forward packets

True

It is possible for a mail client to send e-mail messages over HTTP rather than SMTP

True

Iterated query and recursive query are two different types of query in DNS name resolution

True

Layers four and five of the internet protocol stack are implemented in the end systems but not in the routers in the network core

True

Personal devices such as tablets and cellphones can be treated as end systems in the context of computer networking

True

Routing and Forwarding are the two key network-core functions

True

Two distinct web pages can be sent over the same persistent connection

True

Which option is a type of DNS records? - A - NS - CNAME - all

all

A browser will generate header lines as a function of _____ - browser type and version - user configuration of browser - whether the browser has a cached version of the requested object - all of the above

all of the above

In computer networking, firewall can be deployed in _____ - routers - end systems - servers - all of them

all of them

client/server architecture

always on host permanent IP address data centers for scaling may have dynamic IP addresses do not communicate directly with each other

sockets

analogous to door, sending process shoves message out door sending process relies on transport infrastructure on other side of door to deliver message to socket at receiving process

aside

applications with P2P architectures have client processes & server processes

Physical Layer

bits "on the wire", actually sends the data across the network. The other layers get the data ready to be sent

Local DNS name servers ______ - obtain resource records from Web caches - never cache resource records - cache resource records, but discard them after a period of time that is on the order of a few days - cache resource records and never discard

cache resource records, but discard them after a period of time that is on the order of a few days

Which option is used to maintain User-server states in HTTP protocol? - cookies - flash - memory - buffer

cookies

calculate transmission rate

d[nodal processing] = d[proc] + d[queue] + d[trans] + d[prop]

d trans = transmission delay

d[trans] = L/R

Link Layer

data transfer between neighboring network elements - Ethernet, 802.111 (WiFi), PPP - frame

Protocols

define format, order of messages sent and received among network entities, and actions taken on message transmission receipt

routing

determines source-destination route taken by packets

cable network multiplexing

different channels transmit different frequency bands

What do end systems connect to in Ethernet network?

ethernet switch

Why layering?

explicit structure allows identification, relationship of complex systems pieces modularization eases maintenance, updating system

In computer networking, the process of moving packets from a router's input to the appropriate router output is defined as _______ . - storing - routing - forwarding - delivering

forwarding

Packet Switching

hosts break application layer into packets forward packets from one router to the next, across links on path from source to destination allows more users to use the network!

Internet Exchange Point (IXP)

hub where the backbone intersects with local and regional networks and where backbone owners connect with one another

Which option is NOT an advantage of web caching? - It can serve as an additional hard drive for end users - it can help to reduce traffic on an institutions access link - it can enable content providers to effectively deliver content - it can help to reduce response time for client request

it can serve as an additional hard drive for end users

Which statement is NOT true about web caching? - it can enable content providers to effectively deliver content - it can help to reduce response time for client request - It cannot be larger than 8g - It can help to reduce traffic on an institutions access link

it cannot be larger than 8g

which of the following servers does not strictly belong to the hierarchical DNS architecture? - Top-level Domain Servers - Local DNS Name Servers - Authoritative DNS servers - Root DNS servers

local DNS name servers

The transfer of an html file from one host to another is _____ . - loss tolerant and time sensitive - loss-intolerant and time sensitive - loss-intolerant and time insensitive - none of the above

loss-intolerant and time insensitive

Application Layer Protocols

messages exchanged e.g. request, response message syntax, fields & how they're dilenated message semantics rules for when and how processes send & respond to messages open protocols: RFC's, HTTP, SMTP

forwarding

move packets from router's input to appropriate router output

For the web application, the user agent is _______ - the users monitor - the users mouse - the users keyboard - none of them

none of them

packet transmission delay = L(bits) / R(bits/sec)

packets of length L, transmission rate R

Which address will be used to direct data to correct process at a node after the data was already forwarded to the node? - MAC - physical - Port - IP

port

client process

process that initiates communication

server process

process that waits to be contacted

Transport Layer

process-process data transfer TCP, UDP - segment

bit

propagates between transmitter / receiver pairs

Which option is NOT a method in HTTP/1.1 ? - GET - PULL - PUT - POST

pull

Two key network-core functions

routing and forwarding

Network Layer

routing of datagrams from source to destination (IP, routing protocols) - datagram

unguided media

signals propagate freely, e.g. radio

Guided Media

signals propagate in solid media: copper, fiber, coax

Which statement is NOT true about CDN (content distribution network)? - stores copies of content at CDN nodes - can deliver video content - subscriber will be directed to the central CDN server to access the requested content - there could be multiple copies for the same content

subscriber will be directed to the central CDN server to access the requested content

Application Layer

supporting network applications (FTP, SMTP, HTTP) - message

Session Layer

synchronization, checkpointing, recovery of data exchange

SMPT is used - to transfer messages from mail server to a user agent - to define the format of message headers - to transfer messages from one mail server to another - all of them

to transfer messages from one mail server to another

In the OSI model, which layer is responsible for the process to process data transfer? - Physical layer - Network layer - Transport layer - Application layer

transport layer

Ethernet

typically used in companies universities etc 10, 100, 1G, 10Gbps transmission rates

UDP service

unreliable data transfer between sending and receiving process

Suppose a DNS resource record has Type=MX. Then - value is the hostname of the mail server that has the alias hostname Name - value is the hostname of the DNS server that is authoritative for Name - value is the IP address of the mail server that has the alias hostname Name - None of them

value is the hostname of the mail server that has the alias hostname Name

physical link

what lies between transmitter and receiver

In networking security, _____ refers to: attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic

DoS

what transport service does an app need?

Data integrity, Timing, Throughput, Security

What is the data unit sent/received over the Network layer in OSI model? - message - segment - datagram - frame

Datagram