NET+ 3/4

Standby UPS

provides continuous voltage to a device by switching to the battery when it detects a loss of power from the wall outlet

TCP Three-Way Handshake Step 1

request for a connection (SYN)

TCP Three-Way Handshake Step 2

response to the request (SYN/ACK)

IGP (interior gateway protocols)

used by interior routers and border routers within autonomous systems and are often grouped according to the algorithms they use to calculate best paths: Distance-vector routing protocols Link-state routing protocols

TCP operates in

in the Transport layer of OSI model Connection-oriented protocol TCP ensures that a connection or session is established by using a three-step process called a three-way handshake

TCP/IP

is open and routable Protocols add a header to data inherited from the layer above it

TCP/IP comes with a set of utilities that can help track down most TCP/IP related problems

netstat tracert or traceroute pathping

Static routing

network administrators configures a routing table to direct messages along specific paths Example - a static route between a small business and its ISP

Path MTU Black Hole

messages are being lost for no apparent reason If suspected, use the ping command to determine the largest size message that can successfully traverse a path to its destination (ping -l)

Brownout

momentary decrease in voltage

Surge

momentary increase in voltage due to lightning strikes, solar flares, or electrical problems

Layer 2 TCP/IP Core Protocols

packet is passed to Data Link layer on NIC, which encapsulates data with its own header and trailer, creating a frame

Routing metrics

properties of a route used by routers to determine the best path to a destination: Hop count Theoretical bandwidth and actual throughput Delay, or latency, on a potential path Load, or the traffic or processing burden Routing cost, or a value assigned to a particular route Reliability of a potential path Topology of a network

Airflow for rack system

In a typical rack system, airflow through the chassis is typically designed to move from front to back Rack-monitoring systems should be installed to sound an alarm if the overall temperature rises too much

IDF

Intermediate Distribution Frame

Ethernet is a Layer 2 standard that:

Is flexible Capable of running on a variety of network media Offers excellent throughput at a reasonable cost Ethernet II is the current Ethernet standard

Default Route-

Is the backup route when no other route is known.

NICs belong to both the Physical and Data Link layer because they:

Issue data signals and assemble/disassemble data frames Interpret physical addressing information Perform routines that determine which node has the right to transmit data

traceroute -

Linux, UNIX, and OS X system use the traceroute utility to send UDP messages to a random port on the destination node (concept is the same as tracert)

MDF

Main Distribution Frame

NAS

Network Attached Storage- is a specialized storage device or group of storage devices that provides centralized fault tolerant data storage for a network Contains its own file system optimized for saving and serving files Reads and writes from its disk significantly faster than other types of servers Can be easily expanded without interrupting service Should be fault tolerant

Layer 3 TCP/IP Core Protocols

Network layer adds it own header and it now becomes a packet

Layer 1 TCP/IP Core Protocols

Physical layer on the NIC receives the frame and places the transmission on the network Receiving host de-encapsulates the message at each layer in reverse order and presents payload to the receiving applications

Routing protocols

Are used by route to determine the best path Routers rate the reliability and priority of a routing protocol's data based on these criteria:

Layers 7, 6, and 5 TCP/IP Core Protocols

Data and instructions, known as payload, are generated by applications.

UDP

User Datagram Protocol Makes UDP more efficient than TCP Useful for live audio or video transmissions over the Internet Also more efficient for carrying messages that fit within one data packet

structured cabling

TIA/EIA's joint 568 Commercial Building Wiring Standard Also known as structured cabling Describes the best way to install networking media to maximize performance and minimize upkeep Apply no matter what type of media, transmission technology, or networking speeds are involved Based on hierarchical design and assumes a network is based on the star topology

Building and Maintaining Network Documentation

To adequately manage a network, record the following: Network diagrams Physical topology Access methods Protocols Devices Operating systems Applications Configurations

Discovering Neighbor Devices

a process used by routers to learn about all of the devices on their networks On IPv4 networks, neighbor discovery is managed by ARP with help from ICMP IPv6 devices use Neighbor Discovery Protocol (NDP) to automatically detect neighboring devices and automatically adjust when neighboring nodes fail or are removed

Gateway of last resort

a router that accepts all unroutable messages from other routers The default route points to the gateway of last resort

A router

-joins two or more networks and pass packets from one network to another

ARP

(Address Resolution Protocol) ARP is a protocol used to maintain a database that maps IP addresses to MAC addresses on the local network ARP relies on broadcasting ARP table - the database of IP-to-MAC address mappings To view ARP table arp -a

IS-IS

(Intermediate System to Intermediate System) - an IGP and link-state routing protocol Uses a best-path algorithm similar to OSPF's Is designed for use on interior routers only (unlike OSPF) Not handcuffed to IPv4 (like OSPF) so it's easy to adapt to IPv6 Service providers generally prefer IS-IS because it's more scalable than OSPF

ICMP

(Internet Control Message Protocol) ICMP - a Network layer core protocol that reports one the success or failure of data delivery examples: PING and TRACERT

OSPF

(Open Shortest Path First) - an IGP and a link-state protocol used on interior or border routers Introduced as an improvement to RIP Imposes no hop limits (unlike RIP) Uses a more complex algorithm for determining best paths Demands more memory and CPU power than RIP, but keeps network bandwidth to a minimum and provides a very fast convergence time

UPS

(Uninterruptible Power Supply) UPS - a battery-operated power source directly attached to devices and to a power supply Prevents undesired fluctuations of power from harming the device or interrupting its services

Layer 4 TCP/IP Core Protocols

- Usually TCP or UDP adds a header to the payload

pathping

- a Windows utility that combines elements of both ping and tracert to provide deeper information about network issues along a route Sends multiple pings to each hope along a route, then compiles information into a single report A disadvantage of pathping is the amount of time it takes to run Shorten running type by limiting the number of queries per hop with the -q parameter

Administrative distance (AD)

- a number indicating the protocol's reliability

netstat

- displays TCP/IP statistics and details about TCP/IP components/connections on a host Information that can be obtained from the netstat command includes: The port on which a particular TCP/IP service is running Which network connections are currently established for a client How many messages have been handled by a network interface since it was activated

Rack systems

- provide mounting hardware for network equipment to optimize the use of square footage in equipment rooms Come in a standard 19-inch frame, but may also come across a 23-inch rack that includes the entire width of the rack Racks may be wall- or ceiling-mounted, or freestanding on the floor Racks are measured in rack units (RU or U)

Half-duplex

- signals may travel in both directions over a medium but in only one direction at a time

BGP (Border Gateway Protocol)

- the only current EGP and is known as the "protocol of the Internet" Can span multiple autonomous systems A path-vector routing protocol that communicates via BGP-specific messages that travel between routers Can be configured to follow policies that might avoid a certain router or instruct a group of routers to prefer a particular route The most complex of the routing protocols

EGP (exterior gateway protocols)

- used by border routers and exterior routers to distribute data outside of autonomous systems The only EGP currently in use is BGP

Online UPS

- uses the AC power from the wall outlet to continuously charge its battery, while providing power to the device through its battery

tracert or traceroute (cont'd) -

A trace test might stop before reaching the destination for one of three reasons: The device the trace is attempting to reach is down It's too busy to process lower-priority messages such as UDP or ICMP It does not accept the UDP or ICMP transmissions being sent because a firewall blocks these types of messages

Cable installation tips to prevent Physical layer failures:

When terminating twisted-pair cabling, don't leave more than 1 inch of exposed cable before a termination Do not exceed the cable's prescribed bend radius Use a cable tester to verify that each cable segment transmits data reliably

tracert

Windows tracert utility uses ICMP echo requests to trace the path from one networked node to another, identifying all intermediate hops between the nodes

Routing table

a database that maintains information about where hosts are located and the most efficient way to reach them Routers rely on them to identify which router is the next hop to reach a particular destination host Routing tables contain IP addresses and network masks that identify a network that a host or another router belongs to

Wiring schematic

a graphical representation of a network's wired infrastructure In detailed form, it shows every wire necessary to interconnect network devices

Auto Negotiation

allows the NIC to select the best link speed and duplex that is also supported by the neighboring device If you specify a particular speed and duplex that is not supported by a neighboring device The result is a speed and duplex mismatch and transmission will fail

Data rooms

are often serviced by HVAC systems separate from the rest of the building Specialized products can monitor the critical factors of a data closet's environment: Temperature Humidity Airflow conditions

Connectivity devices-

are specialized devices that allow two or more networks or multiple parts of the same network to connect and exchange data Known by the highest OSI layer they read and process

Dynamic routing

automatically calculates the best path between two networks and maintains this information in a routing table Router can detect problems with failed or congested routes and reroute messages through a different path

Generator

backup power source, providing power redundancy in the event of a total blackout Can be powered by diesel, liquid propane gas, natural gas, or steam Generators can be combined with large UPSs to ensure that clean power is always available If an organization relies on a generator, fuel levels and quality should be checked regularly

Blackout

complete power loss

Border routers

connect an autonomous system with an outside network

TCP Three-Way Handshake Step 3

connection established (ACK) After the three initial messages, the payload or data is sent

Network diagrams

diagrams provide broad snapshots of a network's physical or logical topology Useful for planning where to insert a new switch or determining how a particular router, gateway, or firewall interact

Exterior routers

direct data between autonomous systems

Interior router

direct data between networks within the same autonomous system

Noise

fluctuation in voltage levels caused by other devices on the network or EMI

Full-duplex, also called duplex

signals are free to travel in both directions over a medium simultaneously

Simplex

signals may travel in only one direction Sometimes called one-way or unidirectional

Convergence time

time it takes to recognize a best path in the event of a change or network outage