FSU ISM 4220 Chapter 3
What is policy-based configuration?
-In SDN, creating policies that are automatically translated into configuration changes on individual devices ex. For a company that manages servers for several different customers, a policy might be that the servers of one customer must never be able to communicate with the servers of other customers. Another might be that expensive transmission links between the company's sites should be shut down at night so that less expensive transmission links are used to handle the lower traffic at night.
What is Software-Defined Networking?
-SDN -a radically new way to configure switches, routers, access points, and other devices
What is the Simple Network Management Protocol?
-SNMP -the protocol that allows a general way to collect rich data from various managed devices in a network -in the network operations center, a computer runs a program called the SNMP manager -the manager communicates with a large number of managed devices, such as switches, routers, access points, firewalls, servers, and PCs
Who talks directly to devices within SNMP?
-SNMP agents: a hardware or software functionality on a managed device that communicates with the SNMP manager -SNMP Get: a command sent by the manager that asks an agent for information about its managed device
Where does SNMP data go?
-SNMP management information base (MIB) -allows network administrators to understand the traffic flowing through the network and is the basis for network visibility
What is traffic shaping?
-a more fundamental way to deal with congestion is to limit what traffic enters the network in the first place -traffic goes through edge router (a router at the edge of the network between an organization and its Internet service provider) -this router has an access control list (ACL) that specifies what to do with each type of traffic (some approved, some forbidden) -forbidden are rate limited
What are the three techniques to deal with momentary traffic peaks?
-add more capacity: given randomness of traffic peaks, they will still occur but be rarer and shorter; adding capacity is expensive in terms of transmissions facilities but adds no ongoing management labor and is a good tradeoff -assign a priority level: priority level assigned to frames or packets, based on their tolerance for latency and loss; VoIP has high priority, email has low -QoS guarantees: extreme approach; guarantee traffic flows such as VoIP meaning no matter if peak or not, this traffic will always get through
What are SDN application programs?
-allow the administrator to do complex tasks with SDN doing remarkably little work compared to manual configuration ex. one of the applications in the figure is a traffic segmentation program that manages changes in access when new servers are added or released by a customer
How does SNMP manage security?
-by NOT using SNMP Set: a command from the manager to the agent to change the configuration of a managed device; hackers can cause chaos if they get hands on this -SNMP Trap: alarms that there is an issue
What do network management tools do?
-costly to purchase and require considerable labor to operate, but they reduce labor expenses more than they cost -enable network administrators to fix problems far more rapidly and to quickly make network changes -allow network administrators to send commands to individual devices to change the way they operate -individual devices can detect something wrong or at least suspicious and send messages called alarms to the network management software
What speed do certain applications need?
-email and messaging can operate at any speed -high-definition video and full-disk backups need higher speeds than we generally get today
What are leased lines used for?
-if the sites are miles apart, they will be connected by leased lines from a telephone carrier -point-to-point links between pairs of sites that are "always on," so they are always available
What is the forwarding function?
-in SDN, the switch, router, or access point function that sends incoming frames or packets back out -consumes nearly all of a switch's or router's resources
Why are companies more worried about latency and jitter today?
-most networks were engineered to carry traditional data such as e-mail and database transmissions -as VoIP, video, and interactive applications have grown in importance, companies have begun to worry more; design necessary
What are the elements of centralized network management?
-network managers use network management programs (a program run by the network administrator on a central computer) to reduce their work -these programs allow managers working in centralized network operation centers (NOCs) to comprehend (and change) what is going on throughout their networks
What are the two sets of SDN APIs?
-northbound: govern communication between application programs and the controller -southbound: standardize communication between the SDN controller and the individual switches, routers, and other devices they configure
What is the Network Visualization Program?
-separate from SNMP -takes results from the MIB and interprets the data to display results in maps, find root causes for problems, and do other tasks -lack of specification allows network visualization program vendors to innovate without being constrained by standards
What are SLAs?
-service level agreements -contracts that guarantee levels of performance for various metrics such as speed and availability -penalties if the network does not meet its service metrics guarantees -like insurance policies: take effect when something bad happens; guarantees worst case scenarios (min speed) -often written on percentage basis -rarely deal with residential
What are APIs?
-standardized interfaces between programs ex. the SDN controller has a set of APIs that application programs use to talk to it in a standardized way. This means that any software company can write application programs to work with the SDN controller. It also means that these applications can run on SDN controllers from other vendors if these vendors follow the same APIs (enable competition)
What are network QoS metrics?
-stands for quality of service -the quantitative measures of network performance that define what "working well" means and measure how well the network is providing its service -these metrics track the service quality that users receive
What is network availability?
-the ability of the network manager to see what is going on throughout the network -provides an understanding of network traffic trends and errors needed for planning -to achieve network visibility, every device must frequently send information about its configuration, traffic data, and error data
What is latency?
-the amount of network delay -measured in milliseconds (ms)
What is jitter?
-the average variability in arrival times (latency) -voice over IP (VoIP) and streaming media are highly sensitive to jitter; make voices sound jittery
What is a SDN controller?
-the device that manages the control function for multiple switches, routers, and other forwarding devices -when changes are made on the controller, new forwarding rule sets are sent to the affected devices
What is the Ping?
-the oldest network visibility tool -if a network is having problems, a network administrator can simply Ping a wide range of IP addresses in the company and when a host receives a Ping, it should send back a reply -if it replies, it is reachable. If it does not, there is a problem -reports round-trip latency which is the time between sending a message and getting a response -reachability of devices with errors
What is error rate?
-the percentage of bits or packets that are lost or damaged during delivery -when the network is overloaded, error rates can soar because the network must drop the packets it cannot handle -at the physical layer, it is common to measure bit error rates; at the internet layer, it is common to measure packet error rates
What is the control function?
-the policy-based reconfiguring of network devices -consumes most of the administrator's time in dealing with the devices
What is the problem with SDN APIs?
-there are several families -Cisco Systems, which dominates sales in routers and many switch categories, has its own approach that is designed to keep its routers and switches expensive by not stripping the control function out of them but offering many of the benefits of SDN -Amazon Web Services, which hosts servers for other companies by creating its own SDN routers, which are far cheaper than commercial routers because their control functions have been removed
How can networks become more reliable?
-through redundancy -adding an extra transmission line -redundant transmission links ensure that if a link fails there can still be transmission among at least some sites that would not be able to communicate after the failure
What does network design always start with?
-traffic requirements -traffic analysis: how much traffic must flow over each of the network's many individual transmission links (two, three, & four-site analysis; count by each location) *note: review graphics of traffic analysis on page 82
When people talk about speed in the IT world, what do they really mean?
-velocity of transmission rate -sends more bits each second -measured in bits per second (bps)
What is traceroute?
a program that gives the round-trip latency to every router along the route to a particular destination host and identifies links with unusually high latency
What are momentary traffic peaks?
a surplus of traffic that briefly exceeds the network's capacity, happening only occasionally
How are aggregate throughout and individual throughout different?
aggregate: throughout shared by multiple users; individual users will get a fraction of this throughout individual: the actual speed a single user receives; usually much lower than aggregate throughout in a system with shared transmission speed equation: aggregate throughout divided by the number of active users at the moment
What can help reduce the amount of work on network management chores?
automation
What are percentage of time elements in SLAs?
for instance, an SLA on speed might guarantee a speed of at least 480 Mbps 99.9% of the time -means that the speed will nearly always be at least 480 Mbps but may fall below that 0.1% of the time without incurring penalties
What are state sponsored hackers?
individuals employed by the government and gain top-secret information to damage information systems of other governments
What are white hat hackers?
individuals professing hacker skills and using them for defensive purposes and have permission from the system owner aka security analysts
What are suicide hackers?
individuals who aim to bring down critical infrastructure for a "cause' and are not worried about jail time or punishment
What are hacktivists?
individuals who promote a political agenda by hacking, especially by defacing or disabling websites
What are gray hat hackers?
individuals who work both offensively and defensively at various times
What are black hat hackers?
individuals with extraordinary computing skills, resorting to malicious and destructive activities aka crackers
What are cyber terrorists?
individuals with wide range of skills, motivated by religious or political beliefs to create fear by large-scale disruption of computer networks
What is availability?
the ability of a network to serve its users
What is control agility?
the ability to rapidly change how the network operates when conditions change
What is control agility?
the ability to take policy-based control actions rapidly when conditions require change
What is the rated speed?
the speed the standard or the carrier specifies
What is throughout?
the speed you actually receive
What is multiplexing?
transmits the traffic of multiple conversations over a shared trunk link, as opposed to unshared access links; this saves money downside: your individual throughout will vary with traffic, especially if the system is near capacity
What are script kiddies hackers?
unskilled hacker who compromises systems by running scripts, tools, and software developed by real hackers
