CompTIA Network+ Test Prep – Network Terminology 2

Analog Signaling – continuous variable states of waves, measured by
Amplitude – signal strength compared to a reference value
Frequency – number of cycles completed by the wave w/in a unit of time. Measured in Hertz.
Phase – relative state of the wave when timing began. Measured in degrees

P 7-23 Connection Services – give us reliable transmissions – next 3 layers

**Flow control – how much data can be sent without overflowing the buffers
**Error control – is the data accurate
**Sequence control (network layer) – packets are broken down / put back together correctly

**Physical Address (MAC), Logical Network Address, Service Address
Method:

Logical Network Address – routers use this for proper internetwork path selection. Logically distinguishes two different networks in an internetwork. P 8-6 = diagram

Method:

Service Address – Each service on a computer (entity) must have its own address. This identifies a specific upper-layer software process or protocol. Multiple service addresses on each computer. Does not identify a unique router. AKA a socket or window, by certain protocols.
P 8-6:

Logical Network Address = network
Physical Device Address = computer
Service Address = program (process) that is sending / receiving the data

Circuit Switching – establishes a dedicated channel through a network. Only lasts for the duration of the conversation between sender & receiver. Sets up a logical path and maintains it for the session.

Switching – route between sender & receiver. (multiple pathways between computers – switch between pathways)
Message Switching – no dedicated path between stations. Conversations divided into messages. Messages are packaged with destination address, and then transmitted. Intermediate devices receive message, store it briefly, then transmit to the next device. Store and forward

Packet Switching – combination of circuit & message switching. Break messages into packets, each with its own delivery information & sequence #, can take different paths through a network to a device. Each device chooses the best path for every packet. Received out of order, the sequencing # is used to reconstruct message.

1. Virtual Circuit Packet Switching – (logical connection) – sender & receiver agree on path to be taken & other parameters for duration of conversation.
2. Datagram Packet Switching – no logical connection – packets are sent to a network, devices determine whether or not to accept is using LLC level addressing.

Route Discovery – how networks determine the correct path for data. Path determination is called routing. Process used to identify routes and maintain Route tables.

Route tables = lists that indicate the next hop to which packets should be directed. (ie, next step in the journey)

Cost = use routing algorithms to find most efficient path through the network.

P 8-15 – list
Hop count = routers
Tick count = time
Relative expense = figure used by people

Methods:

Distance Vector Method – routers build route tables by broadcasting and combining tables from nearby routers. Broadcast contains entire route table. Oldest method. Gets update information from its neighbors. Increments hop, tick, and relative expense from other tables. After update, broadcasts its changes. Process of updating is called convergence. Uses 2nd hand information to built its tables.

Method:

Link-State Method – router broadcasts the state of its immediate connections – more efficient – similar to distance vector, but only broadcasts changes. More efficient than Distant Vector. More complicated to configure – used in larger networks. Uses 1st hand information to build its tables.

Process:

Route Selection – router figures out the best path to take through an internetwork.

Method:

Dynamic Route Selection – routers calculate the next hop by smpling the network. Each router along the path selects the next stop.

**recovers from failed or overworked routers, but costs more.

Method:

Static Route Selection – path is designated by network administrator, or by a device. Routers along the path do not select the next stop.

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Note: These are notes from my lectures as an IT instructor. Notes are from 1999-2001, so there may be little relevance to contemporary technologies. Still, it seemed like a shame to delete all of this work, so here they are. I hope someone finds them helpful.