Computer Networking Semester 2 Unit 11

jitter

All packets experience some latency. When successive packets experience varying amounts of latency, resulting in their arriving out of order, the user experience is degraded

adaptability

Because NAS devices can store and retrieve data for any type of client (providing the client can run TCP/IP), NAS is appropriate for networks that use a mix of different operating systems, multimedia types, and even IoT components that require centralized storage space.

static configuration

Both hosts are manually configured to handle the division of labor between the redundant links according to particular rules without the ability to compensate for errors.

-runts -giants -jabber -ghosts -packet loss -discarded packets -interface resets

The effective utilization of network monitoring tools can help identify and prevent many types of complications, such as the following:

hot spare

hot spare

Clustering

A technique of grouping multiple devices so they appear as a single device to the rest of the network.

FCoE (Fibre Channel over Ethernet)

A technology that allows FC to travel over Ethernet hardware and connections.

SNMP Get Response

The agent sends a response with the requested information.

traffic analysis

The examination of network traffic for patterns and exceptions to those patterns.

DSCP (Differentiated Services Code Point)

The first 6 bits of the 8-bit DiffServ field in an IPv4 packet which indicates to network routers how the data stream should be forwarded.

EF (Expedited Forwarding)

A DiffServ forwarding specification that assigns each data stream a minimum departure rate from a given node.

polling

A network management application's regular collection of data from managed devices.

traffic policing

A traffic-shaping technique in which the volume or rate of traffic traversing an interface is limited to a predefined maximum.

snapshot

A frequently saved, incremental backup of the data's state at a specific point in time, typically containing only information about changes made since the last backup and not capable of being used to fully restore lost data.

HA (high availability)

A system that functions reliably nearly all the time.

HSRP (Hot Standby Routing Protocol)

Cisco's proprietary standard that assigns a virtual IP address to a group of routers.

SNMP Get Request

The NMS sends a request for data to the agent on a managed device.

fault

The malfunction of one component of a system.

standby and online

UPSes are classified into two general categories:

AF (Assured Forwarding)

A DiffServ forwarding specification that prioritizes data handling, but provides no guarantee that on a busy network messages will arrive on time and in sequence.

Event Viewer

A GUI application that allows users to easily view and sort events recorded in the event log on a computer running a Windows-based operating system.

iSCSI (Internet SCSI)

A Transport layer protocol used by SANs that runs on top of TCP to allow fast transmission over LANs, WANs, and the Internet.

full backup

A backup in which all data on all servers is copied to a storage medium, regardless of whether the data is new, changed, or unchanged.

incremental backup

A backup in which only data that has changed since the last full or incremental backup is copied to a storage medium.

differential backup

A backup method in which only data that has changed since the last full or incremental backup is copied to a storage medium even if earlier differential backups have been made.

UPS (uninterruptible power supply)

A battery-operated power source directly attached to one or more devices and to a power supply (such as a wall outlet) that prevents undesired fluctuations of the wall outlet's AC power from harming the device or interrupting its services.

blackout

A complete power loss. It could cause significant damage to your network. For example, if a server loses power while files are open and processes are running, its NOS might be damaged so extensively that the server cannot restart and the NOS must be reinstalled from scratch. A backup power source, however, can provide power long enough for the server to shut down properly and avoid harm.

backup

A copy of data or program files created for archiving or safekeeping.

load balancer

A device that distributes traffic intelligently among multiple computers or connections.

jabber

A device that handles electrical signals improperly, usually affecting the rest of the network.

SAN (storage area network)

A distinct network of storage devices that communicate directly with each other and with other networks.

cold spare

A duplicate component that is not installed, but can be installed in case of a failure. Relying on a cold spare results in an interruption of service.

QoS (quality of service)

A group of techniques for adjusting the priority a network assigns to various types of transmissions.

availability

A measure of how consistently and reliably a file, device, or connection can be accessed by authorized personnel.

utilization

A measure of the actual throughput used as a percentage of available bandwidth.

brownout

A momentary decrease in voltage; also known as a sag. An overtaxed electrical system can cause brownouts, which you might recognize in your home as a dimming of the lights. Such voltage decreases can cause computers or applications to fail and potentially corrupt data.

surge

A momentary increase in voltage due to lightning strikes, solar flares, or electrical problems;might last only a few thousandths of a second, but can degrade a computer's power supply; are common; You can guard against them by making sure every computer device is plugged into a surge protector, which redirects excess voltage away from the device to a ground, thereby protecting the device from harm

LACP (Link Aggregation Control Protocol)

A protocol currently defined by IEEE's 802.1AX standard that dynamically coordinates communications between two hosts on aggregated connections.

CARP (Common Address Redundancy Protocol)

A protocol that allows a pool of computers or interfaces to share one or more IP addresses.

baseline

A record of how a network operates under normal conditions.

NMS (network management system) server

A server or workstation that collects data from multiple managed devices at regular intervals.

VIP (virtual IP address)

A single IP address that represents a cluster of devices.

NAS (network attached storage)

A specialized storage device or group of storage devices that provides centralized fault-tolerant data storage for a network.

Syslog (system log)

A standard for generating, storing, and processing messages about events on a system.

DiffServ (Differentiated Services)

A technique for ensuring QoS by prioritizing traffic.

SNMP Trap

An agent can be programmed to detect certain abnormal conditions that prompt the generation of SNMP Trap messages, where the agent sends the NMS unsolicited data once the specified conditions on the managed device are met

managed objects

Any characteristic of a device that is monitored, including components such as a processor, memory, hard disk, or NIC, or intangibles such as performance or utilization.

optimization

Compared to a typical file server, a NAS device contains its own file system that is optimized for saving and serving files. Because of this optimization, NAS reads and writes from its disk(s) significantly faster than other types of servers.

noise

Fluctuation in voltage levels caused by other devices on the network or EMI. Some noise is unavoidable on an electrical circuit, but excessive noise can cause a power supply to malfunction, immediately corrupting program or data files and gradually damaging motherboards and other computer circuits.

ghosts

Frames that are not actually data frames, but aberrations caused by a device misinterpreting stray voltage on the wire.

automatic failover

In the event of a component failure, the ability of a redundant component to immediately assume the duties of the failed component.

runts

Packets that are smaller than the medium's minimum packet size.

giants

Packets that exceed the medium's maximum packet size.

CoS (Class of Service)

Quality control techniques performed at Layer 2 on Ethernet frames.

distributed switching

The centralized control of many VMs' access to a network across a server cluster.

collector

The computer that gathers event messages from generators

generator

The computer that is monitored by a syslog-compatible application and that issues event information

ault management

The detection and signaling of device, link, or component faults.

event log

The service on Windows-based operating systems that records events.

loss-tolerant

Transmissions that can tolerate occasional loss of data without compromising the user experience.

delay-sensitive

Transmissions that will suffer significantly compromised user experiences if portions of the transmission are delayed, such as with voice and video transmissions.

discarded packets

ackets that arrive at their destination, but are then deliberately discarded, or dropped, because issues such as buffer overflow, latency, bottlenecks, or other forms of network congestion delayed them beyond their usable time frame.

VRRP (Virtual Router Redundancy Protocol)

A standard that assigns a virtual IP address to a group of routers.

FC (Fibre Channel)

A storage networking architecture that runs separately from Ethernet networks to maximize speed of data storage and access.

IB (InfiniBand)

A storage networking architecture that serves a few niche markets and falls on the difficult end of the installation and configuration spectrum.

packet drops

Packets that are damaged beyond use, arrive after their expiration, or are not allowed through an interface.

-amount of power needed -period of time to keep a device running -line conditioning -cost

To decide which UPS is right for your network, consider a number of factors:

online UPS

Uses the AC power from the wall outlet to continuously charge its battery, while providing power to a network device through its battery. In other words, a server connected to an online UPS always relies on the UPS battery for its electricity. Because the server never needs to switch from the wall outlet's power to the UPS's power, there is no risk of momentarily losing service. Also, because the UPS always provides the power, it can handle noise, surges, and sags before the power reaches the attached device. As you can imagine, online UPSes are more expensive than standby UPSes.

SNMP Walk

With this one command, the NMS can issue the equivalent of a sequence of SNMP Get Next messages to walk through sequential rows in the MIB database.

expansion

NAS hardware can be easily expanded without interrupting service. You can physically install a new hard drive without shutting down the system. The NAS device recognizes the added storage and immediately adds it to its pool of available reading and writing space.

interface resets

Repeated resets of the connection, resulting in lower-quality utilization; caused by an interface misconfiguration.

SNMP Get Next

The NMS might then request the next row of data in the MIB database.

network management

The assessment, monitoring, and maintenance of all aspects of a network.

-SNMPv1 -SNMPv2 -SNMPv3

Three versions of SNMP exist:

MTTR (mean time to repair)

The average amount of time required to repair a device or restore a service.

MTBF (mean time between failures)

The average amount of time that will pass before the next failure of a device or service is expected to occur.

error rate

The calculated percentage of how often bits are damaged in transit.

fault tolerance

The capacity of a system to continue performing despite an unexpected hardware or software malfunction.

Load balancing

The distribution of traffic over multiple components or links to optimize performance and fault tolerance.

-surge -noise -brownout -blackout

The following list describes power flaws that can damage your equipment:

SNMPv1 (Simple Network Management Protocol version 1)

This is the original version, released in 1988. Because of its limited features, it is rarely used on modern networks.

SNMPv2 (Simple Network Management Protocol version 2)

This version improved on SNMPv1 with increased performance and slightly better security, among other features.

SNMPv3 (Simple Network Management Protocol version 3)

This version is similar to SNMPv2, but adds authentication, validation, and encryption for messages exchanged between managed devices and the network management console. the most secure version of the protocol

-generator -collector

two possible roles for computers participating in logging events:

-static configuration -passive mode -active mode

Most of these devices offer similar configuration options, such as:

Link aggregation

The seamless combination of multiple network interfaces or ports to act as one logical interface.

redundancy

The use of more than one identical component, device, or connection for storing, processing, or transporting data.

OID (object identifier)

A number assigned each managed object.

Traffic shaping

Manipulating certain characteristics of packets, data streams, or connections to manage the type and amount of traffic traversing a network or interface at any moment.

packet loss

Packets lost due to an unknown protocol, unrecognized port, network noise, or some other anomaly.

standby UPS, also called an SPS (standby power supply)

Provides continuous voltage to a device by switching virtually instantaneously to the battery when it detects a loss of power from the wall outlet. Upon restoration of power, the standby UPS switches the device back to AC power. The problem with standby UPSes is that, in the brief amount of time it takes the UPS to discover that power from the wall outlet has faltered, a device may have already detected the power loss and shut down or restarted. Technically, a standby UPS doesn't provide continuous power; for this reason, it is sometimes called an offline UPS. Nevertheless, standby UPSes may prove adequate even for critical network devices, such as servers, routers, and gateways. They cost significantly less than online UPSes.

MIB (Management Information Base)

The list of objects managed by an NMS, as well as the descriptions of these objects.

performance management

The ongoing assessment of how well links and devices are keeping up with the demands placed on them.

active mode

The port is set to automatically and actively negotiate for link aggregation using LACP. This allows for fault tolerance should one or more links fail, as LACP will automatically reconfigure active links to compensate. In reality, this is the most common configuration for all ports involved in link aggregation, and provides the most protection against link misconfigurations or failures.

passive mode

The port passively listens for LACP-defined link aggregation requests, but will not initiate the request.

port aggregation

The seamless combination of multiple network interfaces or ports on Cisco devices to act as one logical interface.

NIC teaming

The seamless combination of multiple network interfaces or ports on Windows devices to act as one logical interface.

-SNMP Get Request -SNMP Get Response -SNMP Get Next -SNMP Walk -SNMP Trap

There are a few, key SNMP messages used to communicate between the NMS and managed devices. As you can see in the following list, most of these conversations are initiated by the NMS: