· 10 years ago · Sep 12, 2016, 01:04 AM
110.0.0.0-10.255.255.255 Private network
2127.0.0.1-127.255.255.255 Private network
3172.16.0.0-172.31.255.255 Private network
4192.168.0.0-192.168.255.255 Private network
5
6Class Start End Subnet mask CIDR notation
7A 0.0.0.0 127.255.255.255 255.0.0.0 /8
8B 128.0.0.0 191.255.255.255 255.255.0.0 /16
9C 192.0.0.0 223.255.255.255 255.255.255.0 /24
10D 224.0.0.0 239.255.255.255 not defined N/A
11E 240.0.0.0 255.255.255.255 not defined N/A
12
13CIDR Host bits Subnet mask Hosts in subnet
14/8 24 255.0.0.0 16777214
15/9 23 255.128.0.0 8388606
16/10 22 255.192.0.0 4194302
17/11 21 255.224.0.0 2097150
18/12 20 255.240.0.0 1048574
19/13 19 255.248.0.0 524286
20/14 18 255.252.0.0 262142
21/15 17 255.254.0.0 131070
22/16 16 255.255.0.0 65534
23/17 15 255.255.128.0 32766
24/18 14 255.255.192.0 16382
25/19 13 255.255.224.0 8190
26/20 12 255.255.240.0 4094
27/21 11 255.255.248.0 2046
28/22 10 255.255.252.0 1022
29/23 9 255.255.254.0 510
30/24 8 255.255.255.0 254
31/25 7 255.255.255.128 126
32/26 6 255.255.255.192 62
33/27 5 255.255.255.224 30
34/28 4 255.255.255.240 14
35/29 3 255.255.255.248 6
36/30 2 255.255.255.252 4
37/31 1 255.255.255.254 2
38/32 0 255.255.255.255 1
39
40-Packet switching=is great for bursty data: best effort delivery, better for resource sharing. Congestion: packet delay in the router’s queue, packet loss due to queue overflow. Protocols overhead for reliable data transfer, congestion and flow control
41-Circuit switching=is great for voice and video: timing, latency, and jitter guarantee. Dedicated resources (bandwidth). Complex mechanisms lead to high cost for equipment and management
42-Total delay of a node=proc delay+trans delay+prop delay+queuing delay
43-Host to host delay=3Xtrans delay+prop delay+other delays
44-ttrans=L/R=L/(R/Channels)
45-tprop=d/c
46-Assume best-effort transmission for router queing
47-Internet protocol stack: US DoD Model
48Application Layer=Network applications: HTTP, SMTP, FTP
49Transport Layer=end-to-end data transfer,Transmission control protocol (TCP): reliable transport with overhead, User Datagram Protocol (UDP): best effort delivery with little overhead, Stream Control Transmission Protocol (SCTP): reliable transport based on transaction.
50Network Layer=routing of datagrams from source subnet to destination subnet,IP and routing protocols
51Data Link Layer=data transfer between neighboring nodes via physical medium, Ethernet, WiFi
52Physical Layer=Bits propagate using copper, fiber and radio waves
53-Nyquist frequency=fs>=2Xfm,Ts=1/fs
54-Synchronous transmission=permits a bit stream under the control of a clock signal and the bits.
55-Asynchronous transmission=allows the bits to be synchronized, but the bytes are not.
56-Isochronous transmission=transmits asynchronous data over a synchronous data link: ideal for voice and video.
57-Isochronous transmission assigns each data source a fixed amount of time to transmit (one time slot) within each cycle through every source.
58-Frequency Division Multiplexing (FDM): transmit multiple signals over non-overlapping frequency bands.
59-Wave Division Multiplexing (WDM): transmit each signal on a different wavelength (optical frequency) over a single optical fiber.
60-Time Division Multiplexing (TDM): transmit multiple signals during non-overlapping time slots in a round-robin fashion.
61-Code Division Multiplexing (CDM) employs spread-spectrum technology and assigns orthogonal codes to transmitters to allow signal multiplexing.
62-Cyclic redundancy check (CRC) is employed to detect a single burst of errors: employed in the Ethernet MAC layer, not physical layer.
63-Parity bit can be used to detect odd number of errors: data-plus-parity bit stream is even or odd. Even=no errors, Odd=errors.
64-Shannon's Channel Capacity=CWlog2(1+S/N) bps, W=fs/2 is the bandwidth, S=signal power, N=noise power,S/N=signal power to noise power ratio,
65S/NdB=10log10(S/N) dB.
66-Ethernet frame struc=Preamble(8bytes), Dest Mac addr(6bytes), Src Mac addr(6bytes), Type(2bytes), Payload(46-1500bytes), FCS(4bytes).
67-Address resolution protocol (ARP)=Station A wants to send datagram to Station B, and B’s MAC addr is not in A’s ARP table. Station A broadcasts (Dest MAC addr=FF-FF-FF-FF-FF-FF) ARP query packet, containing B's IP addr to all nodes on LAN. Station B receives ARP packet, replies to Station A with its MAC addr as unicast. Station A caches (saves) IP-to-MAC addr pair in its ARP table/cache until information times out. There is no ARP server, so nodes create ARP tables without involving network administrator.
68-CRC=add the same number of CRC-# as 0s to the data bits(insidebox #) and divide (XOR) by the other number. Remainder gets appended to data bits.
69-ip fragmentation=header(20bytes)+payload(max of 1480).offset=payload/8=0x,1x,2x,3x,etc. fields=length=total,id=x,fragflag=1,offset,bytes(from 0 to payload).
70-Open Shortest Path First (OSPF)=Link-state (LS) algorithm, LS packet dissemination, All routers have complete topology map at each node, link cost information, Shortest Path First (SPF) computation using Dijkstra’s algorithm.
71-wildcard mask=Subnet mask of 255.255.255.0, Wildcard mask of 0.0.0.255.
72-Border Gateway Protocol (BGP) is the de facto standard and provides each AS a means to=Obtain subnet route advertisements from neighboring ASs, Propagate route advertisement to all AS-internal routers, Determine optimal routes to subnets based on route advertisement and policy, Allow a subnet to advertise its existence to remainder of Internet.
73-Link State or Distance Vector=Link-State Routing requires significant computation and memory resources, topology information is flooded (high bandwidth and storage overhead), and every path to every node computed locally in each node (high processing overhead in a large network). Typically used only inside an AS: OSPF.
74-Advantages of Distance Vector for BGP include hiding details of the network topology, less computing and communication in each node, and nodes determine only “next hop†toward destination.
75-multi-homed AS=maintains connections to more than one other AS. Better availability: This allows the AS to remain connected to the internet in the event of
76a complete failure of one of their connections. Traffic filter: Block traffic from one AS passing through on its way to another AS Border/Gateway router is direct link to routers in other AS’s.
77-stub AS=is only connected to one other AS. This may be a waste of an AS number if the network's routing policy is the same as its upstream AS’s.
78-transit AS=provides connections through itself to other networks. For example, network A can use network B as transit AS to connect to network C. ISPs are always transit AS’s because they provide connections from one network to another.
79-AS Path (to AS)=Destination prefix(#.#.#.#/#),next hop(AS #)
80-Destination AS and next hop routing table of single router=dest AS(AS #),next hop(#.#.#.# of first interface it has to pass) is X,1-X-2,1-X-3,1-X-4
81-AS Advertisement=adv subnet(never changes),next hop(output IP),AS path(AS where it came from). Then adv subnet(same),next hop(new output IP), AS Path(#,#).
82-Connection-oriented service has three phases=connection setup, data transfer, termination. Packets are always received in order, Routers on the source-to-destination path maintain state information for each connection.
83-ATM’s virtual circuit (VC) network provides network-layer connection-oriented service=A virtual circuit is a source-to-destination path mimicking a telephone circuit. ATM is used in the Internet backbone, from the subscriber edge router to the core routers. Provider Edge Router=at the edge of an ISP network. Subscriber Edge Router=at the edge of the subscriber network, owned by an organization.
84-Connectionless or datagram service doesn’t have setup and termination phases=Packets are typically received out of order. Ethernet-based IP provides connectionless service.
85-DHCP allows host to dynamically get IP address when joining network. DHCP server provides 4 pieces of information: IP address, Subnet mask, Gateway IP
86address, DNS IP address. Allow IP address reuse; renew IP address already in use. Host holds an IP address only while actively connected.
87-DHCP Client/Server, DHCP procedure=1.Host broadcasts “DHCP Discover†message.2.DHCP server responds with “DHCP offer†message. 3. Host requests IP address: “DHCP request†message.4.DHCP server sends address: “DHCP ACK†message.
88-Internet Control Message Protocol (ICMP)=ICMP runs on top of IP, in parallel with TCP, UDP and SCTP. ICMP is triggered when an IP packet encounters a problem, e.g., time exceeded or destination unreachable. ICMP packet sent back to the source IP address: Includes the error information (e.g., type and code) and excerpt of the original data packet for identification. Source host receives the ICMP packet, inspects the excerpt of the packet (e.g., protocol and ports) and informs the socket that should receive the error information.
89-ARP process=stationA broadcasts ARP query packet to all machines (Src IP station A) with stationB's IP in Dest IP and Dest. MAC FF:FF:FF:FF:FF:FF. StationB receives ARP packet, replies to stationA with Src IP stationB, Dest IP stationA, Src MAC Station B, Dest MAC Station A. StationA saves stationB's MAC and IP in its ARP table.
90
91-transport protocols=Provide inter-process communication between applications running on two different end hosts (supported by OS) by relying on the bottom 3 layers for delivering information. Sending host breaks application-layer messages into segments, passes down to network layer. Receiving host reassembles segments into messages, passes up to application layer.
92-TCP=Transmission Control Protocol (TCP) for reliable delivery (RFCs 793, 1122, 1323, 2018, 2581). Connection setup and teardown, congestion control , flow control, byte-order preservation. Applications: data exchange, bank transactions, email, web.
93-SCTP=Stream Control Transmission Protocol (SCTP) for reliable delivery (RFC 4960). Developed for signaling system 7 (SS7) for IP telephony, possesses all advantages of TCP. Parallel delivery of multiple objects for a transaction (images in a web page), improved security (denial of service protection) and reliability (redundant paths to host).
94-UDP=User Datagram Protocol (UDP) provides datagram (unreliable) delivery (RFC 768). Connectionless service with no handshaking between UDP sender and receiver. No delay for connection establishment and no connection state to maintain: no allocation of buffer size and sequence numbers. Each UDP segment is handled independently of others. Connectionless, best-effort delivery with no message order. When the order is important, application handles the sequence number of packets (as in Real-Time protocol (RTP)). Applications: voice/audio/video delivery. No resource allocation for UDP: no bandwidth, delay, delay jitter guarantees.
95-TCP services=Connection-oriented, reliable, flow control, congestion control. Uses sequence numbers, ACK, sliding window, connection establishment and termination. Cannot assure: Timing guarantee, delay jitter guarantee, minimum data rate.
96-UDP services=connectionless, unreliable, low overhead, low latency. Cannot assure: Flow control, congestion control, timing/jitter guarantee, minimum data rate.
97-TCP versus SCTP=Consider TCP for http to send a webpage containing multiple objects: If the base file of http has a lost segment, then no display of the page will occur until retransmission. If one of the image files has a segment lost, then the following objects cannot be sent until this image segment is retransmitted correctly. By replacing TCP with SCTP for http: Multiple objects are sent in parallel. When some objects have errors, the correctly received objects can be displayed first. The retransmitted object will be displayed when it’s correctly received.
98-Socket is a 2-tuple (UDP=dest IP, dest port) or a 4-tuple (TCP=src IP, src port, dest IP, dest port) of IP address and port number.
99-Channel with errors: some bits corrupted: Receiver detects errors without acknowledging (ACK) receiving the packet. Sender retransmits the data that were not acknowledged.
100-Lossy channel with errors: some data missing (buffer congestion) and some bits corrupted: Receiver detects errors but cannot be sure if packet is lost or delayed. Sender must wait for acknowledgment (ACK).
101Sender retransmits data after some time if no ACK arrives.
102-Congested network and lossy channel with errors: Reduce transmission rate based on network feedback; otherwise, more loss and worse congestion.
103-Methods for Reliable Delivery=Checksum is used to detect corrupted data at the receiver. No ACK for corrupted packet. Sequence numbers are used to detect unACKed datagram and reassemble datagrams back in order. Retransmission by sender of lost or corrupted data. Timeout based on estimates of round trip time (RTT). Fast retransmit mechanism for repetitive requests from receiver.
104-Three-way handshake to establish connection=Client sends a SYN (open) to the server. Specifies client initial sequence number (ISN). Advertises buffer size. Server returns a SYN acknowledgment (SYN ACK). Server allocates buffer: flow control information (e.g., RcvWindow). Specifies server ISN. ACK # = client ISN + 1. Client sends ACK, which may contain data. RTT is estimated. ACK # = server ISN + 1. Data transfer follows.
105-Close connection: 4-way handshake=Client initiates closing socket: Client sends TCP FIN control segment to server. Server receives FIN, replies with ACK. Sends FIN. Client receives FIN, replies with ACK. Enters “timed waitâ€: It will respond with ACK to received FINs. After the wait is timed out, socket is
106closed. Server receives ACK. Connection closed.
107-RTT=Estimated RTT is used to determine if packet delivery is successful. Sender retransmits a packet after a timeout (based on RTT) in waiting for ACK.
108-Transmission time for a message=# of packets of a message x RTT
109-Link utilization=(L/R)/(RTT+(L/R))=N x Dtr/(RTT+Dtr). Dtr=transmission delay=L/R. N=number of packets in the first burst.
110-Pipelining=Sender sends a series of packets without waiting for ACK. Sequence numbers are used. Flow control: do not exceed the buffer at receiver. Dramatically improves link utilization.
111-N x MSS < available buffer size in the receiver. MSS=maximum segment size (TCP).
112-Available window size of the receiver limits the effective data rate B to N x MSS/RTT. RTT=round-trip time in seconds.
113-IP packet=Smaller than Maximum Transmission Unit (MTU). E.g., up to 1500 bytes on an Ethernet.
114-TCP packet=IP payload with a TCP header and data inside. TCP header is typically 20 bytes long except in a 3-way handshake.
115-TCP segment=No more than Maximum Segment Size (MSS) bytes. E.g., up to 1460 consecutive bytes from the stream on an Ethernet.
116-HL (4 bits) – TCP header length or data offset in 32-bit words: minimum 20 and maximum 60 bytes, allowing up to 40 bytes of options in the header.
117-R (3 bits) – reserved, should be set to zero.
118-Flags (or control bits) – nine 1 bit flags.
119-NS – ECN-nonce concealment protection (RFC3540).
120-CWR – congestion window reduced. One of two flags in the TCP header for congestion control.
121-ECE – ECN-Echo. Second congestion control flag. ECN: explicit congestion notification.
122-URG – indicates that the urgent pointer field is significant.
123-ACK – indicates the ACK field is significant.
124-PSH – push data to the other end.
125-RST – reset the connection.
126-SYN – synchronize sequence numbers; only the first packet sent from each end has SYN set.
127-FIN – close the connection.
128-Source port (16 bits) – identifies the sending port.
129-Destination port (16 bits) – identifies the receiving port.
130-Sequence number (32 bits) – has a dual role: If the SYN flag is set to 1, then this is the initial sequence number. The sequence number of the actual first data byte transmitted and the corresponding ACK are this sequence number plus 1. If the SYN flag is 0, then this is the accumulated sequence number of the first data byte of this segment for the current session.
131-Acknowledgment number (32 bits) – if the ACK flag is set, the value of this field is the next sequence
132number that the receiver is expecting. This acknowledges receipt of all prior bytes (if any). The first
133ACK sent by each end acknowledges the other end's initial sequence number itself, but no data.
134-Receive window size (16 bits) – the number of window size units (bytes) beyond the sequence number in the ACK field that the sender of this segment is currently willing to receive.
135-Checksum (16 bits) – for error-checking of the header and data.
136-Urgent pointer (16 bits) – if the URG flag is set, then this field is an offset from the sequence number
137indicating the last urgent data byte.
138-Twrap=(2^31)/(B/8)=1.72 x (10^10)/B seconds
139-EstimatedRTT = (1-alpha)*EstimatedRTT + alpha*SampleRTT. Typical value for alpha=0.125.
140-Timeout Interval=EstimatedRTT + 4xDevRTT. DevRTT=(1-beta) x DevRTT+beta x |SampleRTT-EstimatedRTT|. Typical value for beta-0.25.
141-Non-persistent HTTP=Establishes one TCP connection. One object is sent over a TCP connection. Closes that TCP connection. Repeat this process for each object. HTTP/1.0 uses non-persistent HTTP.
142-Persistent HTTP=Multiple objects can be sent over a single TCP connection between client and
143server. No need to establish/close multiple connections. HTTP/1.1 uses persistent connections in default mode.
144-Non-persistent HTTP=Total time = 2RTT + file transmit time.
145-Non-persistent Serial TCP connections=There is only one connection.
146-Non-persistent Parallel TCP connections=There are multiple connections. Most browsers open multiple parallel TCP connections.
147-Persistent HTTP=A single connection for all objects. Server keeps connection open after sending response.
148Subsequent HTTP messages between same client and server sent over the opened connection.
149-Persistent without pipelining=Client issues new request only when previous response has been received. One RTT for each referenced object.
150-Persistent with pipelining=Default in HTTP/1.1. Client sends multiple requests without waiting for response objects. One RTT for all the referenced objects.
151-Time to download a file=queuing delay + (one-way) propagation delay for the request + transmission delay (L/R) + (one-way) propagation delay.
152-File transfer protocol (FTP)=Transfer file to/from remote FTP server (RFC 959): TCP based, client/server model. Client contacts server at port 21 and establishes a control connection. Port 21 for control functions: login, client authentication, change directory, etc. Client browses remote directory by sending commands over control connection. When server receives file transfer command, a data connection is established.
153-Active FTP=data connection is initiated by the server (port 20). After transferring one file, FTP server closes data connection and opens another TCP data connection to transfer another file. In active mode, client sends the server the port number (PD > 1023) over the control connection. Client will listen at P D and server initiates the connection (at port 20).
154-Passive FTP=client side establishes the data connection. Passive mode is used when client is behind a firewall, unable to accept incoming TCP connections. Client opens two random unprivileged ports locally Pc > 1023 and Pc + 1. The first port Pc connects to the server on port 21. Server opens a random unprivileged port Ps > 1023, sends P s to client over control connection. Client then initiates the connection from port Pc + 1 to port Ps on server to transfer data.
155-SFTP=Secure-shell (SSH) file transfer protocol (SFTP) is a new secure protocol (not FTP over SSH). Using SSH connection, SFTP follows a request-response model: Each request and response contains a sequence number and multiple requests may be pending simultaneously. Each request has one or more response messages that may be returned in the result.
156-SSH=SSH is an application layer protocol for secure remote login and other secure network services over an insecure network.
157-Email=Four components: user agents (UA), mail servers, simple mail transfer protocol (SMTP) for sending
158email, and mail access protocols (IMAP/POP3) for email retrieval.
159-DNS=An infrastructure for translating between a name and IP addresses, DNS is an application-layer protocol used by hosts to query DNS servers.
160-Root name servers are contacted by local DNS name server that cannot resolve a name. Root name servers know which servers are responsible for the top-level domains (TLD).
161-Top-level domain (TLD) servers are responsible for .com, .edu, .org, .net, .gov, etc, and all top-level
162country domains uk, fr, ca, jp.
163-Authoritative DNS servers are organization’s DNS servers, providing authoritative hostname to IP
164mappings for organization’s servers (e.g., Web, mail). Provide authoritative answers to a query based on direct knowledge (not cached information). Can be maintained by organization or service provider.
165-DNS resolvers are programs that obtain information from name servers in response to client
166requests for mapping from name to IP address.
167-zone transfer=from primary authoritative to secondary authoritative server
168-BIND=Berkeley Internet Name Domain (BIND) uses recursive server and caching server synonymously.
169-Forwarder and Firewall=A caching name server does not necessarily perform the complete recursive lookup itself. Instead, it forwards some or all of the queries that it cannot find from its cache to another
170caching name server, called forwarder. Caching servers unable to pass packets through the firewall would forward to the server that can traverse the firewall, and that server would query the Internet DNS servers on the internal server's behalf.
171-Recursive queries=need access to the root servers which is provided via the 'type hint' statement: root servers’ IP addresses are in a file.
172-RR=contain the information requested by DNS queries and are stored in a universal format Illustrative RR format: (name, [pref.], value, type, [ttl]), (<URL>, <IP>, A)
173Universal RR format=name [ttl] [Class] Type [pref.] value, <URL>. IN A <IP>
174-Type=A=name is host’s name; value is IP address.
175-Type=NS=name is domain name; value is name of authoritative name server for this domain.
176-Type=MX=name is domain name; value is name of mail server for the domain; a preference value is designated for each mail server if multiple MX RR’s in a domain.
177-Type=CNAME=name (<URL>) is alias name for “canonical†(real) name; value is canonical name (<extraname>.<URL>); <URL> (name) is really <extraname>.<URL>.
178-Type=AAAA=IPv6 host address; maps a DNS domain name to an IP version 6 128-bit address.
179-ttl=time to live in cache; 32 bit integer for the number of seconds.
180-DNS Message header=ID: 16 bit # for query and reply. A particular query and reply use same ID #.
181-DNS Flags=QR bit=query (=0) or reply (=1). RD bit=recursion desired. RA bit=recursion available. AA bit=Authoritative Answer. RCODE (Response code)=4 bits. Code=3=Name Error (no existent domain name, etc.).
182Code=0=no error.
183-DNS message format=Question=Name and type for a query. Answer=RRs as the answer. Authority records=Resource records point toward another authoritative name server. Non-recursive reply contains no answer and delegates to another DNS server. Additional=Additional “helpful†RR, e.g., suggestion to ask another DNS server (plus server’s IP address) that may have answer.
184-Forward resolution=name to IP address mapping, forward DNS zones.
185-Reverse zone=IP address to name mapping.
186-Stability=the ability of a system to stay within normal operating conditions when subjected to disturbance.
187-Controllability=the ability to move a system within its configuration space using only certain admissible manipulations.
188-Observability=the ability to determine the states of the system through sensor measurements.
189-ICS (Industrial control systems)=Encompass supervisory control and data acquisition (SCADA) systems, distributed control systems (DCS), and Programmable Logic Controllers (PLC) found in the industrial sectors and infrastructure.
190-Control server=hosts the DCS or PLC supervisory control software that communicates with lower-level control devices. The control server accesses subordinate control modules over an ICS network.
191-SCADA Server or Master Terminal Unit (MTU)=acts as the master in a SCADA system. Remote terminal units and PLC devices located at remote field sites usually act as slaves.
192-Remote Terminal Unit (RTU) or remote telemetry unit=is a data acquisition and control unit designed to support remote stations. RTUs are field devices often equipped with wireless radio interfaces to support remote situations where wire-based communications are unavailable. Sometimes PLCs are implemented as field devices to serve as RTUs.
193-Intelligent Electronic Devices (IED)=is a “smart†sensor/actuator containing the intelligence required to acquire data, communicate to other devices, and perform local processing and control.
194-Human-machine interface (HMI)=is software and hardware that allows human operators to monitor the state of a process under control, modify control settings to change the control objective, and manually override automatic control operations in the event of an emergency.
195-Data historian=is a centralized database for logging all process information within an ICS. Information stored in this database can be accessed to support various analyses, from statistical process control to enterprise level planning.
196-Input/output (IO) server=is a control component responsible for collecting, buffering and providing access to process information from control sub-components, such as PLCs, RTUs and IEDs. Can reside on the control server or on a separate computer platform. Also used for interfacing third-party control components, such as an HMI and a control server.
197-Fieldbus network=links sensors and other devices to a PLC or other controller.
198-Control network=connects the supervisory control level to lower-level control modules.
199-Router=is a communications device that transfers messages between two networks.
200-Firewall=protects devices on a network by monitoring and controlling packets using predefined filtering policies.
201-Modem=is used to convert between digital data and a signal suitable for transmission over a telephone line to allow devices to communicate.
202-Remote access points=are distinct devices, areas and locations of a control network for remotely configuring control systems and accessing process data.
203-s1,a1,d1 -> change in direction = s1 -> Y <- d1 = a2, s2=a1. s2,a2,d2 -> no change in direction = s2,a2=s3,a3 and d2!=d3.
204-minimum window size= N(packets) * L(length)
205-Effective Bandwidth=B=N x MSS/RTT = (bps)
206-Twrap=wraparound time(no PAWS)=(2^31 in bits(*8))/(Max effective Bandwidth in bits)
207-Twrap=wraparound time(PAWS)=(2^63 in bits(*8))/(Max effective Bandwidth in bits)
208-Both queuing and propagation delay affect the networked control system performance by
209introducing delay in the feedback loop for sensor measurements and delay in actuator
210commands that respond to the sensor measurements.
211-Enterprise network, supervisory control network, controller network, and fieldbus. In some
212cases, the supervisor control and controller networks are combined into one “control
213network.â€
214-Supervisory control and data acquisition (SCADA) systems, distributed control systems
215(DCS), and programmable logic controllers (PLC)
216-SCADA system controls geographically dispersed assets (plants and processes);
217centralized data acquisition and control are critical to the overall system operation.
218-DCS provides supervisory control of controllers within the same geographic location to
219oversee an entire production process
220-Fieldbus is an industrial networking system for real-time distributed control and exists at the
221bottom of a hierarchy of industrial controller systems. It is typically linked at a PLC, which in
222turn is connected to higher levels of controllers in the system through Ethernet.
223-Foundation Fieldbus H1, ControlNet, PROFIBUS, P-Net, Foundation Fieldbus HSE,
224WorldFIP, and Interbus.
225-Reduced capital expenditure associated with eliminating cables connecting field devices to
226the PLC.
227-A typical type of Layer 2 implementation used in fieldbus is time critical data link layer.
228-The different types of mechanisms used in the medium access layer of a fieldbus are contention based (CSMA), time division multiplexing based (STDMA, ATDMA), and controlled access based (token passing and polling).
229-A hypervisor runs directly upon the host’s hardware, which is known as a bare metal approach, while the hosted virtualization installs and runs the virtualization layer as an application on top of an OS and supports hardware configurations. The hypervisor architecture provides its own device drivers and services whereas the hosted virtualization architecture leverages device drivers and services of a host OS.
230-Hardwareâ€assisted virtualization needs no modification for OS, and privileged and sensitive instructions are carried out in a new CPU execution mode, i.e. root mode Ring 0. That is, the hypervisor/VMM runs in a new mode with full privileges in root mode Ring 0.
231-VM security issues: access control=legitimate users and devices must be authenticated and authorized for accessing their assigned portions of the network/resources;(2)path isolation=the substantiated user device must be mapped to the correct secure set of available resources effectively, e.g. the right VPN/VLAN; and (3) services=the right services have to be accessible to the legitimate set or sets of users and devices, with centralized policy enforcement.
232-IaaS=The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, deployed applications, and possibly limited control of select networking components, e.g., host firewalls.
233-PaaS=The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed applications and possibly application hosting environment configurations.
234-SaaS=The consumer does not manage or control the underlying cloud in frastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited userâ€specific application configuration settings.
235-SMTP=SMTP is used to send mail from client to server and server to server. SMTP uses a persistent connection and has three phases.
236-IMAP4=IMAP4 and POP3 are both used for email retrieval from a server. IMAP keeps all messages in a server and allows users to organize messages in folders, so they can manipulate them. It is more secure than POP3. IMAP maintains user state across sessions.
237-POP3=IMAP4 and POP3 are both used for email retrieval from a server. POP3 by default uses the “download and delete†mode and can also use the “download and keep†mode. Users must download the mails from a mail box. POP3 is stateless across sessions, but it is not secure.
238-Microsoft Messaging Client=The SMTP, POP3, and IMAP4 constitute a set of Internet Standard protocols that e-mail clients use to send, retrieve, and manage email messages. Many clients support MAPI/RPC.
239-Webmail=Webmail uses HTTPS as the mail access protocol and to send mail from client to server.