Term
What are some of the possible services that a link-layer protocol can offer to
the network layer? Which of these link-layer services have corresponding
services in IP? In TCP? |
|
Definition
Framing - packaging data into frames with header fields and content field, exists in both IP and TCP
Link access - MAC (medium access control) controls which nodes have access to a link for frame transmission at which times
Reliable Delivery - Also in transport layer
Error detection and recovery - also in IP and TCP |
|
|
Term
Suppose two nodes start to transmit at the same time a packet of length L
over a broadcast channel of rate R. Denote the propagation delay between the two nodes as dprop. Will there be a collision if dprop < L/R? Why or why not? |
|
Definition
| No, because transmission time is less than propagation delay, so the channel will be idel by the time transmission ends and the next propagation phase begins |
|
|
Term
| Four desirable characteristics of a broadcast channel |
|
Definition
a - When only one node has data to send, that node has a throughput of R bps
b - When there is more than one (M in total) node sending data, the rate for all nodes is ~R/m on average
c - The protocol is decentralized - no one nodes can bring down all functionality.
d - simplicity |
|
|
Term
| Which of the above does slotted ALOHA have? |
|
Definition
| a, b, and d (only partial decentralization, because all clocks in nodes have to be synchronized) |
|
|
Term
| Which of the above does token passing have? |
|
Definition
|
|
Term
Describe polling and token-passing protocols using the analogy of cocktail
party interactions. |
|
Definition
Don't even know what the hell a cocktail party is, so..
polling: master node polls all nodes to see exactly how many frames it can transmit.
token-passing - a special token circulates through the ring and stays with a node if it can transmit. It is now that token's turn to transmit up to a set maximum number a frames. |
|
|
Term
Why would the token-ring protocol be inefficient if a LAN had a very large
perimeter? |
|
Definition
| The token may take a significant amount of time to makes its way around the ring. |
|
|
Term
How big is the MAC address space? The IPv4 address space? The IPv6
address space? |
|
Definition
MAC address space - 48 bits so 2^48
IPv4 - 32 bits - 2^32
IPv6 - 128 bits - 2^128 |
|
|
Term
Suppose nodes A, B, and C each attach to the same broadcast LAN (through
their adapters). If A sends thousands of IP datagrams to B with each encapsulating
frame addressed to the MAC address of B, will C’s adapter process
these frames? If so, will C’s adapter pass the IP datagrams in these frames to the network layer C? How would your answers change if A sends frames with
the MAC broadcast address? |
|
Definition
| If the destination MAC address is B's MAC address, then C will process the frames but not pass them up to the network layer. If the broadcast MAC address is used, C will do both. |
|
|
Term
Why is an ARP query sent within a broadcast frame? Why is an ARP
response sent within a frame with a specific destination MAC address? |
|
Definition
| It has to send the ARP query to get the MAC address associated with that IP address. The response is sent with a specific destination MAC address, because it knows which adapter sent the query. |
|
|
Term
| 7. Consider two subnets which are interconnected by a router. The router has two ARP modules, each with its own ARP table. Is it possible that the same MAC address appears in both tables? Explain. |
|
Definition
| No it is not possible. Each LAN has its own distinct set of adapters attached to it, with each adapter having a unique LAN address. |
|
|
Term
Suppose that N switches supporting K VLAN groups are to be connected via
a trunking protocol. How many ports are needed to connect the switches?
Justify your answer. |
|
Definition
| We can string the N switches together. The first and last switch would use one port for trunking; the middle N-2 switches would use two ports. So the total number of ports is 2+ 2(N-2) = 2N-2 ports. |
|
|
Term
| 1、What does it mean for a wireless network to be operating in “infrastructure mode”? If the network is not in infrastructure mode, what mode of operation is it in, and what is the different between that mode of operation and infrastructure mode? |
|
Definition
| In infrastructure mode of operation, each wireless host is connected to the larger network via a base station (access point). If not operating in infrastructure mode, a network operates in ad-hoc mode. In ad-hoc mode, wireless hosts have no infrastructure with which to connect. In the absence of such infrastructure, the hosts themselves must provide for services such as routing, address assignment, DNS-like name translation, and more. |
|
|
Term
| What are the four type of wireless networks? Which of these types of wireless networks have you used? |
|
Definition
a) Single hop, infrastructure-based
b) Single hop, infrastructure-less
c) Multi-hop, infrastructure-based
d) Multi-hop, infrastructure-less |
|
|
Term
| What is the difference between a permanent address and a care-of address? Who assigns a care-of address? |
|
Definition
| A permanent address for a mobile node is its IP address when it is at its home network. A care-of-address is the one its gets when it is visiting a foreign network. The COA is assigned by the foreign agent (which can be the edge router in the foreign network or the mobile node itself). |
|
|
Term
| What are the purposes of the HLR and VLR in GSM networks? What elements of mobile IP are similar to the HLR and VLR? |
|
Definition
The home network in GSM maintains a database called the home location register (HLR), which contains the permanent cell phone number and subscriber profile information about each of its subscribers. The HLR also contains information about the current locations of these subscribers. The visited network maintains a database known as the visitor location register (VLR) that contains an entry for each mobile user that is currently in the portion of the network served by the VLR. VLR entries thus come and go as mobile users enter and leave the network.
The edge router in home network in mobile IP is similar to the HLR in GSM and the edge router in foreign network is similar to the VLR in GSM |
|
|
Term
| In mobile IP, what effect will mobility have on end-to-end delays of datagram between the source and destination? |
|
Definition
| Because datagrams must be first forward to the home agent, and from there to the mobile, the delays will generally be longer than via direct routing. Note that it is possible, however, that the direct delay from the correspondent to the mobile (i.e., if the datagram is not routed through the home agent) could actually be smaller than the sum of the delay from the correspondent to the home agent and from there to the mobile. It would depend on the delays on these various path segments. Note that indirect routing also adds a home agent processing (e.g., encapsulation) delay. |
|
|
Term
What are the differences between the following types of wireless channel
impairments: path loss, multipath propagation, interference from other
sources? |
|
Definition
| Path loss is due to the attenuation of the electromagnetic signal when it travels through matter. Multipath propagation results in blurring of the received signal at the receiver and occurs when portions of the electromagnetic wave reflect off objects and ground, taking paths of different lengths between a sender and receiver. Interference from other sources occurs when the other source is also transmitting in the same frequency range as the wireless network. |
|
|
Term
What are the differences between the following types of wireless channel
impairments: path loss, multipath propagation, interference from other
sources? |
|
Definition
| Path loss is due to the attenuation of the electromagnetic signal when it travels through matter. Multipath propagation results in blurring of the received signal at the receiver and occurs when portions of the electromagnetic wave reflect off objects and ground, taking paths of different lengths between a sender and receiver. Interference from other sources occurs when the other source is also transmitting in the same frequency range as the wireless network. |
|
|
Term
As a mobile node gets farther and farther away from a base station, what are
two actions that a base station could take to ensure that the loss probability of
a transmitted frame does not increase? |
|
Definition
The two possible ways are, 1) increasing the transmiss
ion power, and 2) reducing the transmission rate. |
|
|
Term
|
Definition
|
|
Term
| Describe the role of the beacon frames in 802.11. |
|
Definition
| APs transmit beacon frames. An AP‟s beacon frames will be transmitted over one of the 11 channels. The beacon frames perm it nearby wireless stations to discover and identify the AP. |
|
|
Term
| True or false: Before an 802.11 station transmits a data frame, it must first send an RTS frame and receive a corresponding CTS frame. |
|
Definition
|
|
Term
| Why are acknowledgments used in 802.11 but not in wired Ethernet? |
|
Definition
| In wired Ethernet, the transmitted can sense the wire and decide if the frame was successfully delivered, so no ACK is necessary. In the wireless scenario, the sender has no idea if the frame was successfully delivered, for two reasons. First, fading or the hidden-terminal problem may mean that interference occurred without the sender knowing. Second, the sender may not be capable of transmitting and listening at the same time, making collision detection impossible. Hence, an ACK is useful. |
|
|
Term
| Describe how the RTS threshold works. |
|
Definition
| Each wireless station can set an RTS threshold such that the RTS/CTS sequence is used only when the frame is longer than the threshold. This ensures that RTS/CTS mechanism is used only for large enough frames. |
|
|
Term
Suppose the IEEE 802.11 RTS and CTS frames were as long as the standard
DATA and ACK frames. Would there be any advantage to using the CTS and
RTS frames? Why or why not? |
|
Definition
Yes. They are still neccessary to avoid the
hidden terminal problem
. The
CTS and RTS frames makes sure a node A sending to B won’t interfer with
another node C also attempting to contact B, even if A and C are unable to see
eachother. |
|
|
Term
|
Definition
| A and C are close/unobstructed enough to transmit to B, but not to each other, and are interfering with each other. |
|
|
Term
What are the differences between a master device in a Bluetooth network and
a base station in an 802.11 network? |
|
Definition
Bluetooth devices organize themselves into a "Piconet" of up to 8 slave devices. One of the devices will be the "master" device. The master's clock determines the Piconet time. The master can change any device from Parked to Slave. Blutooth is also an example of an Ad-hoc network.
A base station or access point is a receiver and transmitter acting as the hub of the WIFI network. Additionally, may also function as the gateway between a wired network and the wireless network. This is also an example of infrastructure mode. |
|
|
Term
| What is the role of the “core network” in the 3G cellular data architecture? |
|
Definition
The 3G core cellular data network connects radio access networks to the public Internet.
The core network interoperates with components of the existing cellular voice network (in particular, the MSC) |
|
|
Term
What is the role of the RNC in the 3G cellular data network architecture?
What role does the RNC play in the cellular voice network? |
|
Definition
typically controls several cell
base transceiver stations. The RNC connects to both the circuit-switched cellular voice network via an MSC, and to the packet-switched Internet via an SGSN. Thus, while 3G cellular voice and cellular data services use different core networks, they share a common first/last-hop radio access network. |
|
|
Term
If a node has a wireless connection to the Internet, does that node have to be mobile? Explain. Suppose that a user with a laptop walks around her house with her laptop, and always accesses the Internet through the same access
point. Is this user mobile from a network standpoint? Explain. |
|
Definition
| No. A node can remain connected to the same access point throughout its connection to the Internet (hence, not be mobile). A mobile node is the one that changes its point of attachment into the network over time. Since the user is always accessing the Internet through the same access point, she is not mobile. |
|
|
Term
What is the difference between a permanent address and a care-of address?
Who assigns a care-of address? |
|
Definition
| A permanent address for a mobile node is its IP address when it is at its home network. A care-of-address is the one its gets when it is visiting a foreign network. The COA is assigned by the foreign agent (which can be the edge router in the foreign network or the mobile node itself) |
|
|
Term
Consider a TCP connection going over Mobile IP. True or false: The TCP
connection phase between the correspondent and the mobile host goes
through the mobile’s home network, but the data transfer phase is directly between the correspondent and the mobile host, bypassing the home network. |
|
Definition
|
|
Term
What are the purposes of the HLR and VLR in cellular (e.g., GSM)
networks? What elements of mobile IP are similar to the HLR and VLR? |
|
Definition
| The home network in GSM maintains a database called the home location register(HLR), which contains the permanent cell phone number and subscriber profile information about each of its subscribers. The HLR also contains information about the current locations of these subscribers. The visited network maintains a database known as the visitor location register (VLR) that contains an entry for each mobile user that is currently in the portion of the network served by the VLR. VLR entries thus come and go as mobile users enter and leave the network. The edge router in home network (or home agent) in mobile IP is similar to the HLR in GSM and the edge router in foreign network (or foreign agent) is similar to the VLR in GSM |
|
|
Term
| What is the role of the anchor MSC in GSM networks? |
|
Definition
| The anchor MSC is the MSC that handled the first call procedure. It will always be in charge of the call. If mobile moves to another MSC the call will go to the anchor MSC and then to the second MSC. If the mobile moves to a third MSC the second MSC will be no longer be part of the call. |
|
|
Term
| What are three approaches that can be taken to avoid having a single wireless link degrade the performance of an end-to-end transport-layer TCP connection? |
|
Definition
Local recovery - Recovers from bit errors at the wireless link when they occur.
TCP Sender awareness of wireless links - This will enable TCP to be aware of the wireless link where ordinarily it would not be. This will make the distinction between cognitive loss and caption loss occurring in the wired and wireless network.
Split connection approaches - The sender and receiver is broken down into 2 transport layer connections 1 from the mobile host to the wireless AP, the other from the AP to the end point. This is widely used in cellular networks. |
|
|
Term
There are two types of redundancy in video. Describe them, and discuss how
they can be exploited for efficient compression. |
|
Definition
Spatial redundancy is the redundancy within a given image. Intuitively, an
image that consists of mostly white space has a high degree of redundancy and can be efficiently compressed without significantly sacrificing image quality. Temporal redundancy reflects repetition from image to subsequent image. If, for example, an image and the subsequent image are exactly the same, there is no reason to reencode the subsequent image; it is instead more efficient simply to indicate during encoding that the subsequent image is exactly the same. |
|
|
Term
Suppose an analog audio signal is sampled 16,000 times per second, and each
sample is quantized into one of 1024 levels. What would be the resulting bit
rate of the PCM digital audio signal? |
|
Definition
2^x = 1024
x = 10 bits per sample
10 * 16,000 = 160,000 bps |
|
|
Term
| Multimedia applications can be classified into three categories. Name and describe each category. |
|
Definition
- Two-way conversational applications,
which are characterized by their stringent requirement on end-to-end delay that includes total time taken to capture, digitize, encode/compress audio/video data, transport them from the source to the destination, and decode and display them to the user.
•Broadcasting services
where the source is live. The
main dissimilarity from the conversational applications
is that it is one-way communication and it can stand more delay.
• On-demand applications
(e.g., video on demand)
where the user requests some stored items and the server delivers them to the user. |
|
|
Term
| Streaming video systems can be classified into three categories. Name and briefly describe each of these categories. |
|
Definition
UDP streaming, HTTP streaming, and adaptive HTTP streaming. Although all
three types of systems are used in practice, the majority of today’s systems employ HTTP streaming and adaptive HTTP streaming (DASH)
(look further into these) |
|
|
Term
| List three disadvantages of UDP streaming. |
|
Definition
- many firewalls block UDP
- due to the unpredictable and varying amount of available bandwidth between server and client, constant-rate UDP streaming can fail to provide continuous playout.
-it requires a media control server, such as an RTSP server,
to process client-to-server interactivity requests and to track client state (e.g., the
client’s playout point in the video, whether the video is being paused or played, and so on) for each ongoing client session. |
|
|
Term
|
Definition
|
|
Term
| With HTTP streaming, are the TCP receive buffer and the client’s application buffer the same thing? If not, how do they interact? |
|
Definition
No, they aren't the same thing.
On the client side, the client application (media player) reads bytes from the TCP receive buffer (through its client socket) and places the bytes into the client application buffer. At the same time, the client application periodically grabs video frames from the client application buffer, decompresses the frames, and displays them on the user’s screen |
|
|
Term
Consider the simple model for HTTP streaming. Suppose the server sends
bits at a constant rate of 2 Mbps and playback begins when 8 million bits
have been received. What is the initial buffering delay ? |
|
Definition
Q = number of bits required before playout begins
x = rate at which bits arrive to the client application buffer
Q/x = 8,000,000 / 2,000,000 = 4 seconds |
|
|
Term
| CDNs typically adopt one of two different server placement philosophies. Name and briefly describe these two philosophies. |
|
Definition
• Enter Deep. One philosophy, pioneered by Akamai, is to enter deep into the access networks of Internet Service Providers, by deploying server clusters in access ISPs all over the world.
• Bring Home. A second design philosophy, taken by Limelight and many other CDN companies, is to bring the ISPs home by building large clusters at a smaller number (for example, tens) of key locations and connecting these clusters using a private high-speed network. Instead of getting inside the access ISPs, these CDNs typically place each cluster at a location that is simultaneously near the PoPs (see Section 1.3) of many tier-1 ISPs, for example, within a few miles of both AT&T and Verizon PoPs in a major city. Compared with the enter-deep
design philosophy, the bring-home design typically results in lower maintenance and management overhead, possibly at the expense of higher delay and lower
throughput to end users. |
|
|
Term
| Several cluster selection strategies were described in Section 7.2.4. Which of these strategies finds a good cluster with respect to the client’s LDNS? Which of these strategies finds a good cluster with respect to the client itself? |
|
Definition
One simple strategy is to assign the client to the cluster that is geographically closest. That is good with respect to the client's LDNS
With respect to the client itself (which may be far from the client's LDNS), anycast the is best option. The idea behind IP anycast is to have the routers in the Internet route the client’s packets to the “closest” cluster, as determined by BGP. |
|
|
Term
Besides network-related considerations such as delay, loss, and bandwidth
performance, there are many additional important factors that go into designing a cluster selection strategy. What are they? |
|
Definition
Load on the clusters is one such factor—clients should not be directed to overloaded clusters.
ISP delivery cost is another factor—the clusters may be chosen so that specific ISPs are used to carry CDN-to-client traffic, taking into account the different cost structures in the contractual relationships between ISPs and cluster operators. |
|
|
Term
| What is the difference between end-to-end delay and packet jitter? What are the causes of packet jitter? |
|
Definition
End-to-end delay is the accumulation of transmission, processing, and queuing
delays in routers; propagation delays in links; and end-system processing delays.
A crucial component of end-to-end delay is the varying queuing delays that a packet experiences in the network’s routers. Because of these varying delays, the time from when a packet is generated at the source until it is received at the receiver can fluctuate from packet to packet |
|
|
Term
Why is a packet that is received after its scheduled playout time considered
lost? |
|
Definition
| A packet that arrives after its scheduled playout time can not be be played out. Therefore, from the perspective of the application, the packet has been lost. |
|
|
Term
| describe two FEC schemes. Briefly summarize them. Both schemes increase the transmission rate of the stream by adding overhead. Does interleaving also increase the transmission rate? |
|
Definition
The first mechanism sends a redundant encoded chunk after every n chunks. The
redundant chunk is obtained by exclusive OR-ing the n original chunks. In this manner if any one packet of the group of n + 1 packets is lost, the receiver can fully reconstruct the lost packet.
The second FEC mechanism is to send a lower-resolution audio stream as the
redundant information. For example, the sender might create a nominal audio
stream and a corresponding low-resolution, low-bit rate audio stream. (The nominal stream could be a PCM encoding at 64 kbps, and the lower-quality stream could be a GSM encoding at 13 kbps.) The low-bit rate stream is referred to as the redundant stream.
Interleaving increases latency, but not bandwidth requirements.. whether or not latency increases transmission rate I'm not sure.. probably. |
|
|
Term
| How are different RTP streams in different sessions identified by a receiver? How are different streams from within the same session identified? How are RTP and RPTC packets(as part of the same session) distinguished? |
|
Definition
| RTP streams in different sessions: different multicast addresses; RTP streams in the samesession: SSRC field; RTP packets are distinguished from RTCP packets by using distinctport numbers. |
|
|
Term
What is the role of a SIP registrar? How is the role of an SIP registrar different
from that of a home agent in Mobile IP? |
|
Definition
Every SIP user has an associated
registrar. Whenever a user launches an SIP application on a device, the application sends an SIP register message to the registrar, informing the registrar of its current IP address.
Bob’s registrar keeps track of Bob’s current IP address. Whenever Bob switches to a new SIP device, the new device sends a new register message, indicating the new IP address.
Dunno how its different from a home agent in mobile IP |
|
|
Term
we discussed non-preemptive priority queuing. What would be preemptive priority queuing? Does preemptive priority queuing make
sense for computer networks? |
|
Definition
| Preemptive priority queueing would be interrupting the transmission of a packet if a higher priority packet is found in the queue during that transmission. This doesn't make sense in computer networking, because of stuff and things. Maybe it is inefficient, or maybe there is no way to return that packet to its place in the queue so it is lost? |
|
|
Term
| Give an example of a scheduling discipline that is not work conserving. |
|
Definition
| A round robin queuing discipline that waits until a class with no packets gets one is an example of a non-work conserving queuing discipline. |
|
|
Term
| Give an example from queues you experience in your everyday life of FIFO, priority, RR, and WFQ. |
|
Definition
FIFO: Line at store
Priority: VIPs in club
RR: whatever..
WFQ: whatever.. |
|
|
Term
| Why would a network manager benefit from having network management tools? Describe five scenarios. |
|
Definition
-Centralized diagnostics on distributed networks (track failures, etc..)
-In case of intrusion/attack, allows session logging, dynamic fire walling and other responses/defenses
-Monitoring of efficiency (throughput, load testing, etc..) and network states. |
|
|
Term
| What are the five areas of network management defined by the ISO? |
|
Definition
• Performance management. The goal of performance management is to quantify,
measure, report, analyze, and control the performance (for example, utilization and throughput) of different network components
• Fault management. The goal of fault management is to log, detect, and respond to fault conditions in the network
• Configuration management. Configuration management allows a network manager
to track which devices are on the managed network and the hardware and
software configurations of these devices.
• Accounting management. Accounting management allows the network manager
to specify, log, and control user and device access to network resources. Usage
quotas, usage-based charging, and the allocation of resource-access privileges all fall under accounting management.
• Security management. The goal of security management is to control access to network resources according to some well-defined policy |
|
|
Term
| service management vs network management |
|
Definition
Service Management - the provisioning of resources such as bandwidth, server capacity, and the other computational/communication resources needed to meet the mission-specific service requirements of an enterprise.
Network Management - Network management includes the deployment, integration, and coordination
of the hardware, software, and human elements to monitor, test, poll, configure, analyze, evaluate, and control the network and element resources to meet the real-time, operational performance, and Quality of Service requirements at a reasonable cost.” |
|
|
Term
Define the following terms: managing entity, managed device, management
agent, MIB, network management protocol. |
|
Definition
The managing entity is an application, typically with a human in the loop,
running in a centralized network management station in the NOC
A managed device is a piece of network equipment (including its software)
that resides on a managed network
In our human analogy, the managed objects might be the departments
within the branch office. These managed objects have pieces of information
associated with them that are collected into a Management Information Base
network management agent, a
process running in the managed device that communicates with the managing
entity, taking local actions at the managed device under the command and control of the managing entity
network management
protocol. The protocol runs between the managing entity and the managed
devices, allowing the managing entity to query the status of managed devices and indirectly take actions at these devices via its agents |
|
|
Term
| What is the role of the SMI in network management? |
|
Definition
SMI defines the data types, an object model, and rules for writing and
revising management information. |
|
|
Term
| What is an important difference between a request-response message and a trap message in SNMP? |
|
Definition
request-response mode in which an SNMPv2 managing entity sends a request to an SNMPv2 agent, who receives the request, performs some action, and sends a reply to the request
Trap messages are used to notify a managing entity of an exceptional situation that has resulted in changes to MIB object values |
|
|
Term
| What is meant by an “SNMP engine”? |
|
Definition
The SNMP engine is the part of an SNMP
implementation that handles the
dispatching, processing, authentication, access control, and timeliness of the SNMP messages |
|
|
Term
| What is meant by TLV encoding? |
|
Definition
TLV (Type, Length, Value) approach to encoding data for
transmission. For each data item to be sent, the data type, the length of the data item,and then the actual value of the data item are sent, in that order. |
|
|
Term
| Two broad classes of symmetric encryption techniques. describe both. |
|
Definition
Block ciphers and stream ciphers.
Block cipher: In a block cipher, the message to be encrypted is processed in blocks of k bits.
For example, if k = 64, then the message is broken into 64-bit blocks, and each block is encrypted independently. The number of mappings is 2^k where k = the number of bits in a block. Possible mapping permutations is (2 ^ k)!
Stream cipher: who the fuck knows |
|
|
Term
|
Definition
provides security at the
network layer. IPsec secures IP datagrams between any two network-layer entities, including hosts and routers. As we will soon describe, many institutions (corporations, government branches, non-profit organizations, and so on) use IPsec to create virtual private networks (VPNs) that run over the public Internet. |
|
|
Term
| Three phases of SSL and describe |
|
Definition
Handshake - establish a TCP connection with
Alice, (b) verify that Alice is really Alice, and (c) send Alice a master secret key,
which will be used by both Alice and Bob to generate all the symmetric keys they need for the SSL session
Key Derivation - Alice and Bob use the MS to generate four keys:
• EB = session encryption key for data sent from Bob to Alice
• MB = session MAC key for data sent from Bob to Alice
• EA = session encryption key for data sent from Alice to Bob
• MA = session MAC key for data sent from Alice to Bob
Data Transfer - SSL breaks the data stream into records, appends a MAC to each record for integrity checking, and then appends and encrypts the record+MAC |
|
|
Term
|
Definition
Confidentiality - prevents sensitive information from reaching the wrong people, while making sure that the right people can in fact get it
Integrity - involves maintaining the consistency, accuracy, and trustworthiness of data over its entire life cycle. Data must not be changed in transit, and steps must be taken to ensure that data cannot be altered by unauthorized people
Availability - is best ensured by rigorously maintaining all hardware, performing hardware repairs immediately when needed, providing a certain measure of redundancy and failover (making sure authorized users have access to data/services) |
|
|
Term
| Message authentication code |
|
Definition
H(m + s) which is a hash of the secret key appended to the message
it is then appended to the message and then sent |
|
|
Term
| Cipher block chaining formula |
|
Definition
c(0) = IV
c(1) = KS(m(1) xor c(0))
c(i) = KS(m(i) xor c(i - 1)). |
|
|
