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Networking Powerpoint 5, 6, and 8
Terms in this set (249)
What are the two network layer functions from chapter four?
(forwarding moves packets
routing determines route)
What are two approaches to structuring network control plane?
which is more traditional?
per router control
logically centralized control
per router is more traditional and logically centralized control is software defined networking
What does this describe? Individual routing algorithm components in each and every router interact with each other in control plane to compute forwarding tables
Per-router control plane
What does this describe?
A distinct (typically remote) controller interacts with local control agents (CAs) in routers to compute forwarding tables
Logically centralized control plane
what is the goal of a routing protocol?
to determine good paths from sending hosts to receiving hosts through network of routers.
what is a path in reference to routing protocols?
sequence of routers packets in their journey to the destination host
what is good in reference to routing protocols?
least cost, fastest, least congested
routing is a top ten network problem true or false
Router Algorithm Classification:
what is global information?
▪all routers have complete topology, link cost info
▪"link state" algorithms
Router Algorithm Classification:
what is decentralized information?
▪router knows physically-connected neighbors, link costs to neighbors
▪iterative process of computation, exchange of info with neighbors
▪"distance vector" algorithms
Router Algorithm Classification:
explain static algorithms
routes change slowly over time
Router Algorithm Classification:
explain dynamic algorithms
routes change more quickly
•in response to link cost changes
What are some characteristics of Dijkstras algorithm?
▪net topology, link costs known to all nodes
▪computes least cost paths from one node ('source") to all other nodes
after k iterations, know least cost path to k dest.'s
Dijkstras algorithm/ link state algorithm:
what does the notation
It describes the link cost from node x to y
** it will equal infinity if x and y are not neighbors. This is because it will be unknown
Dijkstras algorithm/ link state algorithm:
what does the notation
current value of cost part from source to dest. v
Dijkstras algorithm/ link state algorithm:
what does the notation
predecessor node along path from source to v
Dijkstras algorithm/ link state algorithm:
what does the notation
set of nodes whose least cost path definitively known
What type of algorithm uses the bellman ford equation??
distance vector algorithms
also called dynamic programming
in the bellman ford equation what does dx(y) mean?
cost of least cost path from x to y
what is the key idea behind distance vector algorithms?
from time to time each node sends its own distance vector estimates to its neighbors.
when x receives new dv estimate from neighbor it updates its own dv using b-f equation.
in the bellman ford equation what does Dx(y) mean?
estimate of least cost path from x to y
under usual conditions the estimate Dx(y) converges to the actual least cost d(x)y true or false
what does it mean that distance vector algorithms are iteritive,asynchronus and distributed.
iterative,asynchronous algorithms: each local iteration is caused by local link cost change and DV update by message from neighbor.
distributed algorithms each node notifies neighbors only when its DV changes.
In distance vectors there is not knowledge of the entire topology true or false
What is the order of the operations in distance vector algorithms
1) wait for change in local link cost or msg from neighbor
2) recompute estimates
3) if dv to any dest has changed notify neighbors
is it possible to store all destinations in routing tables?
no this is why we have autonomous systems
another word for aggregragate routers divided into regions
autonomous systems also known as domains AS
intra as routing
routing among hosts, routers in same AS
all routers in AS must run same intra domain protocol
routers in different as can run different intra domain routing protocol
gateway router at edge of its own AS has links to routers in other AS'es
inter as routing
routing among AS'es
gateways perform inter domain rouiting as well as intra domain routing
with inter connected AS'es how is the forwarding table configured
by both intra and inter AS routing algorithm
this is where the forwarding table lives
if we need to go out of our system then the edge router will know what to do and transfer to the next autonomous system
Does inter or intra AS routing determine entries for destinations within AS?
Does inter or intra AS routing determine entries for external destinations?
both inter and intra determine entires for external desinations
what does ospf stand for
open shortest path first
what is ospf
its a publicly available open protocol that can be run by many different types of entities
does ospf use dijkstras algorithm?
ospf has a topology map at each node t or f
what is different about how ospf messages are carried versus a traditional message?
ospf is carried directly over ip rather than tcp or udp
is IS IS routing protocol very different from OSPF?
no they are nearly identitcal
what are ospf's advanced features
security: all ospf messages authenticated to prevent malicous intrusion
multiple same costs paths allowed
for each link multiple cost metrics for different TOS
integrated uni and multi cast support
heirarchial ospf in large domains
what are the function of area border routers in hierarchial ospf
summarize distances to nets in own area advertise to other area border routers
in hierarcial ospf what are the two levels ?
local area and backbone
** link state advertisements are only in area
** each node has detailed area topology, only know direction to nets in other areas
what does bgp stand for
border gateway protocol
what is bgp known as
glue that holds the internet together
bgp routers are called
bgp is a _____ vector protocol
could be more than one autonomous systems to go through to get to a subnet true or false
explain policy based routing
gateway receiving route advertisement uses import policy to accept or decline paths
***an example would be never go through as2
as policy also determines whther to advertise path to other neighboring ASes
bgp message terminology
open: opens tcp connection to remote bgp peer and authenticates sending bgp peer
update: advertises new path or withdraws old
keep alive: keeps connection alive in absensce of updates; also acks open request
notification: reports errors in previous msg; also used to close connection
what does hot potato routing mean?
find quickest way out of automous system / least intra domain cost
* said not to worry about inter domain cost
what is the difference between a per router control plane and a centralized control plane?
per router: individual routing algorithm components in each and every router interact with eachother in control plane to compute forwarding tables
centralized control plane: A distinct ( typically rmote ) controller interacts with local control agents( dumber hardware devices) in routers to compute forwarding tables
why is a logically centralized control plane better aka software defined networking ?
easier network management: avoid router misconfigurations greater flexibility of traffic flows
table based forwarding allows programming routers
centralized programming is easier, computes tables centrally and distributes them
distributed programming is more difficult, compute tables as result of distributed algorithm implemented in each and every router
open non proprietary implementation of control plane
if you want to change the flow of routing what do you need to do?
change the cost of the links
in traditional routing algorithms is it difficult to change the routes?
SDN data plane switches are fast simple and commoditized true or false
What is the sdn controller known as?
the brains of the operation
the sdn controller maintains _____ state information
sdn controller interacts with network control t or f
SDNs are implemented as distriubted system for performance scalability, fault tolerance, robustness across the internet true or false
do sdn controllers help with redundancy?
what is another way to think of control applications?
they are the brains of control they implement the control
how does load balancing, routing and firewall access get implemented?
through the network control apps in sdn
can sdn controller apps be unbundled?
using sdn you can support many different functions such as routing access control and load balance true or false
what are the components of the sdn controller?
interface layer is at the top
network layer is in the middle
communication layer is at the bottom
what does the communication layer in sdn do?
communicates with control agent devices
also runs snmp protocol
what does the network layer in sdn do?
its responsible for network links and switches
there is also host information, switch information, and everything about the network
what does the interface layer in sdn do?
abstraction apis are located here
who can write to open flow protocol?
where does openflow protocol in sdn operate?
between the controller and the switch
in open flow protocol in sdn what is used to exchange messages?
tcp with optional encryption
what are the three types of classes of open flow messages?
controller to switch
asynchronus (switch to controller)
what are the different types of controller to switch messages in open flow protocol?
open flow switch to controller messages
what is the latest sdn software?
what does icmp stand for?
internet control message protocol
what does icmp do?
protocol used by hosts and routers to communicate network level information
does tracerouting use icmp?
what else is icmp used for?
error reporting if there is an unreachabl;e host, network, port or protocol
echo request/reply used by ping
where is icmp used layer wise?
in the network later above ip
how are icmp messages structured
type, code plus first 8 bytes of ip datagram causing error
what does snmp stand for
simple network management protocol
what are the snmp protocol message types
get request, get next request get bulk request
what does get request / bulk request / next request do?
manager to agent get me data request
what does inform request do in snmp?
manager to manager heres the data
what does setrequest do in snmp?
manager to agent set value
what does response do in snmp?
agent to manager value response to request
what does trap do in snmp?
agent to manager inform manager of exceptional event
end of chapter 5
where is the link layer implimented?
in every host
in adaptors/ network interface cards or on chip
combination of hardware,software and firmware
how does the link layer attach to a hosts system?
what is the responsibility of the sending side in the link layer?
encapsulate datagram in frame
add error checking bits rdt flow control etc
what is the responsibility of the receiving side in the link layer?
looks for errors, rdt flow control
extracts datagram apsses to upper layer at receiving side
what is the transportation analogy for a datagram?
what is the transportation analogy for communication link?
what is the transportation analogy for link layer protocol?
what is the transportation analogy for a travel agent?
what does mac stand for
Media Access Control Address
in the link layer what can be considered as a node?
your phone, your computer, a router that moves packets
what is the difference between half and full duplex
with half nodes at both ends can transmit but not at the same time. full can transmit and receive at the same time.
what are communication channels that connect nodes known as?
what are the link layer services?
framing, link access
reliable delivery between adjacent nodes
half-duplex and full-duplex
what kind of links can there be ?
what is the responsibility of the data link layer?
transferring datagrams from one node to physically adjacent node over a link.
is error detection 100 percent reliable?
why isnt error detection reliable?
protocol may miss some errors but rarely
what does edc stand for
error detection and correction bits
what does the additional D stand for in edc
data protected by error checking may include header fields
what happens when you have larger edc fields
it yeilds better detection and correction
what types of parity checking exsist?
single or two dimensional
what does parity checking do?
checks for errors in transmission
what is the difference between single or two dimensional bit parity
single detects single bit errors
two d detects and corrects single bit errors
what is another common EDC or error detection and correction method other than parity checking?
how does a checksum work?
detects errors / flipped bits in transmitted packet. ( used at transport layer only.)
what are all of the tpyes of error detection and correction
cyclic redundancy check
what is a cyclic redundancy check?
-more powerful error detection coding
-view data bits as a binary number
-widely used in practice
- can detect all burst errors less than r+1 bits
-if there is a non zero remainder error is detected .
two different types of links in multiple access protocols
point to point links such as traditional ethernet
old fashioned ethernet
what is a big problem with multiple access links/ protocols
dealing with collisions
in Mac protocols taxonomy what are the three broad classes
channel partitioning: divide channels into smaller pieces (time slots, frequency, code) allocate piece to node for exclusive use
random access : channel not divided, allows collisions any node can transmit at the entire channel capactiy collisions when 2 or more transmit at the same time
taking turns: nodes take turns, but with nodes with more to send, can take longer turns avoids collisions
time division multiplexing access (tdma)
dividing time based on nodes needing to transmit
good because they get the full node when transmitting
bad because it wastes
FDMA (Frequency Division Multiple Access)
any node can transmit at the same time without warning of collision but the channel itself is divided into sub frequencies
they each get a fraction of the capacity
random access protocols
allow a mechanism to detect collisions, to recover from collisiosn, retransmit and allow us to transmit at the full data rate of channel itself
ALOHA protocol is an example of which of the approach for coordinating access to a broadcast channel:
Random access (quiz question)_
Switches can operate at which of the following layer of the OSI model
network layer and data link layer (apparently quiz question*)
Explain slotted aloha
it works simply, can detect collisions and when they are detected all nodes stop transmitting. when a node obtains a fresh frame it transmits in the next slot. if there is no collision the node can send new frame. if there is a collision node retransmits frame in each subsequent slot until it finds success nodes are sychronized
slotted aloha efficiency is at best ____ percent probability of being able to transmit and ___ percent probability of having a collision and time is going to waste.
pure unslotted aloha differences from slotted aloha
simpler, no synchonization, when frame arrives it transmits, collision probabiliies increase
what was the probability/percentage that a transmission would get through when all nodes had to transmit with pure unslotted aloha?
what concept was CSMA/carrier sense multiple access designed around?
dont interupt when others speak
CSMA/carrier sense multiple access
listen before transmit,
if channel sensed idle transmit entire frame
In CSMA can collisions still occur?
yes, propogation delay can cause nodes to not be able to hear eachother resulting in collisions
what two factors play a role in determining collision probability
distance and propogation
when a collision in csma occurs the _____and ____ are completely wasted
everything must be___________
channels and frames
what does csma/cd stand for?
csma collision detection
what happens to colliding transmissions in csma?
they are aborted to reduce channel waste
which is more difficult collision detection in wired or wireless lans?
wireless lans because received signal strength is overwhelmed by local transmission strength
why is collision detection easier in wired lans?
it measures signal strengths, compares transmitted, recieved signals.
CSMA CD algorithm steps
nic recieves datagram from network layer creates frame
if nic senses channel is idle starts frame transmission, if nic senses channel is busy wait until its idle then transmit
if nic transmits entire frame without detecting another transmission nic is done with frame
if nic detects another transmission while tranmitting aborts and sends jam signal.
after aborting nic enters binary backoff then retransmits frame again
which is more efficient ALOHA or CSMA?
is csma centralized or decentralized?
which protocol shares channel efficiently and fairly at a high load but is inefficient at low loads?
taking turns mac protocol
what is a popular way to describe polling in taking turns strategy
it uses master and slave or main stationand dumb terminals
how does taking turns protocol work when polling is used
there is one controller that decides when nodes transmit
what are the problems with taking turns protocol?
single point of failure ( master or main station)
in taking turns protocol token passing
tokens are passed from one node to the next sequentially
copmuters are connected in a chain like way
types of implimentation for taking turns protocol
multiple access protocols are useful for ________ different types of information
different implimentations can be used to send data up and down stream in mulitple access protocols t or f
what does DOCSIS stand for
data over cable service interface spec
in docsis what is fdm used for ?
over upstream and downstream frequency channels
what is docsis used for ?
allows us to impliment media access control protocols within the cable network
in docsis what is tdm used for ?
is used upstream with some slots assigned to different information being sent up and down
downstream multiple access protocol assigns upstream slots
where is csma/cd used?
where is csma/ca used?
in wireless or 802.11
where is taking turns used?
blue tooth, fddi, token ring
where is channel parititioning used?
time division and frequency division
how many bits is a mac address?
where does a mac address exsist?
the network layer,
going from source to destination
what is a mac address and arp used for?
layer 3 forwarding (network layer) forwarding
what is the function of a mac/lan/physical/ethernet address
used locally to get frame from one interface to another physically connected interface( same network, in ip addressing sense)
when two devices need to communicate with eacohther on the same lan thats when ______ ___________ are used.
what is burned into the network interface card?
how else can mac addreses be set?
programming, software, and the address is burned into rom at the factory level.
said for the purposes of the discussion on the class its just burnt on at the factory level ask in class?
what type of notation is used for mac addressing?
anything connected physically or wirelessly has a mac address in it t or f
there does not exsist two of the same _____ addresses
mac addresses are assigned to the _______ after they purchase them
mac addresses are allocated or administered by _____
mac addresses are like :
ip addresses are like :
options : social security number, postal address
which ones are correct?
mac: social security number
ip: postal address
Ips are unique to the ___ net
you get a different ip addresses when you go to a new location and connect like an airport or a starbucks true or false
even though ip addresses change when connecting to new locations mac addresses stay the same t or f
this means that ip addresses are not portable, they are dependant on the subnet to which the node is attached and that mac addresses are portable in that they can move from one lan to another.
ttl in regards to ip/mac address mapping for some lan nodes means
time to live, time after which address mapping will be forgotten
typically this is 20 minutes
ip/mac address mapping order
<ip address; mac address;ttl>
every device on a network whether it be a switch, iphone or router, computer has an ___ table where it maps the ip address to a known map
how does arp figure out a mac address that is not in their table?
the given entity (entity one) would have to broadcast an arp query packet containing the ip address of the entity(entity b) that has the mac that entity one is interested in.
next once the mac address is sent by entity b, entity A caches/ saves the mac address and syncs it with the ip address in its arp table until information becomes old and times out. (information that times out goes away unless its refreshed)
is arp plug and play?
nodes create their arp tables without intervention from net administrator.
you can pick up the machine and move it to another network plug it in, and as long as it can maintain a valid ip address over time the arp table will be built up of all devices on a particular segment
when communicating between two different networks does arp play an important role?
mac addressing only exsists on the_______ level
even if a mac address of a destination host on another network is known it cannot be communicated to because its on a completely different network
therefore more information is needed
in arp when a frame is being sent to another entity how does this occur?
it first sends a frame to the router and the fields contain the source mac address and the destination address is the mac of the router
then the router removes the link layer info such as mac address and destination mac address of the router and passes the information up to the ip layer so that the routing algorithm can allocate it to the correct place
the source and destination ip never change though but on the frame level the information does change
now there is a mac address of the router interface that the packet will be leaving off and there will be a destination mac address of the computer that its traveling to.
the load was the same but the transportation method changed.
the mac information changes
what type of wired lan technology is dominant?
its cheap and has kept up with the speed race
what are the physical topologies of ethernet?
bus: all nodes in same collision domain and can collide
uses coaxial cable
star: prevails today
active switch in the center
each "spoke" runs a seperate ethernet protocol and nodes do not collide
in ethernet star topology do spokes run seperate ethernet protocols?
what is in the structure of the ethernet frame?
preamble, destination address, source address, type, data payload, crc
what is a preamble used for in an ethernet frame?
to synchronize receiver and sender clock rates
crc or cyclic redundancy checks are built into ethernet frames true or false
is ther handshaking between sending and receiving nics in ethernet?
is ethernet considered reliable or unrealiable?
why is ethernet considered unrelaible
receiving nic does not send acks or nacks to sending nic
data in dropped frames recovered only if initial sender uses high layer rdt (tcp) otherwise dropped data is lost
ethernets mac protocol unslotted csma/cd with binary backoff
switches are ____ layer devices
what do link layer switches do?
store and forward ethernet frames
do switches need to be configured?
switches allow us to have multiple simultanious transmissions without __________________ .
a switch creates a forwarding table to learn about ________addresses from the host that is connected to it and uses the info to _____frames from source to destination
switches are ___ learning
can self learning switches become connected together?
can a large entity be conected by just one switch?
which level do routers work on?
match up each term with the level
datagram is network
frame is link
what is a v lan
virtual local area network
virutal lans allow us to take a port or a number of ports and define them to be their own dedicated lan true or false
what are different characteristics of port based vlans
forwarding between vlans
can vlans be defined based on mac addresses of endpoints rather than switch ports?
explain dynamic membership in relation to vlans
ports can be dynamically assigned among vlans
explain forwarding between vlans how is it done?
can vlans span across multiple switches?
the format of a vlan frame is called
mpls sit between `
layer2 and 2
mpls solveses the problem of how to move packets ____
what does mpls do
it sets a fixed length for label or packet
mpls capable routers can read and look out for ____ length labels as well as source and destiantion ip address
once the label is designed and defined in mpls what is used to forward the information to the destination ip?
what is the difference between ip routing and mpls routing
in ip routing path to destination is determined by desination address along
in mpls routing path to destination can be based on source and destination adress
where do load balancers sit
what layer is dhcp used in
What are the 4 components of network security?
Confidentiality, Authentication, Message Integrity, Access and Availability
What is Confidentiality?
only sender and receiver should know contents of message
What is Authentication?
sender and receiver want to confirm each other's identity
What is Message Integrity?
sender and receiver want to make sure message is unaltered and check without being detected
What is Access and Availability?
Services must be accessible and available
What can malicious users do when referring to different types of attack types?
Eavesdrop( intercept messages), Actively insert messages into connection, Impersonation: can fake or spoof source address in packet or any other field in packet, Hijack: take over ongoing connection by removing sender or receiver, and inserting themselves, Denial of Service: Present use of service by overloading
What is a cipher text attack?
Attacker has the ciphertext she can then analyze
Types of Cipher Text attacks?
Brute force (try all keys), Statisitcal analysis (apply algorithms to text)
What is a Known-plaintext attack?
Trudy has plaintext corresponding to ciphertext
What is a Chosen-plaintext attack?
Trudy can get ciphertext for chosen plaintext
What is symmetric cryptography?
Same key is used to encrypt message and the same is used to decrypt
Requires sender and receiver to know shared secret key
Types of Symmetric Algorithms?
DES - Data Encryption Standard, 3DES, and AES -Advanced Encryption Standard
What is Public Key Cryptography?
Public Key (for encryption) is known to all
Private Key (for decryption) known only to receiver
What is a Digital Signature?
Cryptographic technique analogous to hand-written signature must be Verifiable and Nonforgeable
What key is used to sign a message in Digital Signatures?
Private Key is used to sign
What key is used to prove Bob signed a message using Digital Signatures?
Bob's Public key is used to verify
What are the steps if Bob wants to encrypt and sign the message then send it encrypted to alice?
Bob uses Alice's Public key to encrypt
Bob's Private Key is used to sign message
What are the steps if Bob encrypts and signs the message and Alice wants to verify and read it?
Alice applies her own (Alice's) private key to decrypt the message
Alice applies Bob's public key to the message to verify it was Bob
What is a Certification Authority?
Binds public key to a particular entity, (like an organization)
What are the steps if Alice wants to send a confidential email to Bob?
Generates random symmetric key private key (Ks)
Encrypts message with (Ks)
Also encrypts (Ks) with Bob's public key
Sends both message and Symmetric key
What are the steps if Bob wants to read Alice's email?
Uses his private key to decrypt and recover (Ks)
Uses (Ks) to decrypt message
What layer is IPsec part of?
Does IPsec have the same fields as IP?
what are IPsec Services?
Replay attack prevention
What is IPsec transport mode?
Allows to connect two different computers running same protocol (IPsec)
What is IPsec tunnel mode?
Two routers have IPsec/VPN installed, while the other devices behind it do not have to
What does the IPsec AH (Authentication Header) provide in terms of services?
: Provides source authentication and data integrity but no confidentiality
What does the IPsec ESP (Encapsulation Security Protocol) provide in terms of services?
provides source authentication, data integrity, and confidentially
More widely used than AH
What is a Firewall?
isolates organization's internal network from larger internet, allowing some packets to pass and blocking others
What do firewalls do?
Prevent illegal modification/access of internal data
Ex: replacing webpage with something else
Allow only authorized access to internal network
What are the three types of firewalls?
Stateless packet filters
Stateful packet filters
What is a Stateless packet filters firewall?
Looks at particular packet but without detail Filters packet-by-packet, and drop or accept determined by:
Source IP address, destination IP address
TCP/UDP source and destination port numbers
ICMP message type
TCP SYN and ACK bits
What is a Statefull packet filters firewall?
track status of every TCP connection
Tracks connection setup (SYN), teardown (FIN) and determines whether incoming or outgoing packets "make sense"
Timeout inactive connections at firewall: no longer admit packets
What is an application gateway?
Specific dedicated devices for each application (email, telenet) that determines rules for that application Filters packets on application data as well as IP/UDP/TCP fields
What is an Intrusion Detection Systems?
IDS: intrusion detection system
looks at packet contents (like checking character strings in packets against known viruses and attack strings) checking for attacks and notifying if present
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