Connecting Devices
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Gateway:
device sitting at a network node for interfacing with another network that uses different protocols.[Layer 4 to Layer 7]
Router:
a specialized network device that determines the next network point to which it can forward a data packet towards the destination of the packet. Unlike a gateway, it cannot interface different protocols.[layer 3]
SPANNING TREE ALGORITHM
There are two reasons to an extended LAN to have a loop in it.
the network is managed by more than one administrator; no single person knows the entire configuration of the network.
loops are built in to network on purpose to provide redundancy in case of failure.
Algorithm Selection
Labeled as B1, B2, B3
The algorithm first elects the bridge with smallest ID as the root of the spanning tree.
The root bridge always forwards frames out over all of its ports.
Each bridge computes the shortest path to root and notes which of its ports is on this path.
All the bridges connected to a given LAN elect a single designated bridge that will be responsible for forwarding frames toward the root bridge.
The connecting devices are bridges between the different parts of a document that join all the pieces in a single coherent package. Connection devices show the reader how various sections of information relate and help keep the reader in touch with the flow of information. Documents that do not include connection devices are discontinuous, agitated and difficult to read. The connecting devices are analogous to the traffic signals on which people depend when driving. Imagine a major metropolitan, like Seattle, without bridges, traffic signals or traffic lights to guide drivers through traffic. Chaos and confusion would abound! The same thing happens with a document that lacks connection devices: the reader will have difficulty following the course of the writer's thinking and the document will not flow smoothly.
There are four main types of connection devices. Each of these connecting devices is described below.
Transitions
A transition is a sentence (typically one or two sentences in length) that indicates that the writer has completed a main idea and is moving on to a different idea. The key purpose of transitions is to make the reader know that the writer is moving on to something new. They are used in two places: (a) between paragraphs to indicate a movement from one main idea to another idea, or (b) between main sections of information to signal a movement from one main theme to another.
Signaling
A sign is a phrase or keyword that draws the reader's attention to the specific point the writer is covering. It is a brief "sign" that helps to point out what point a writer is discussing at any given time. Common signs include the following:
• first, second, third, finally
• one two Three
• additionally, in addition, in addition
• complete, summarize, revise, repeat
Signs are typically used in three places: (a) by distinguishing objects in a sequence; (b) in summarizing a series of ideas; and © at the beginning of a sentence.
Forecasts
Previews are used to highlight the information that is coming up and show how this information is organized. Previews help to create appropriate expectations for the reader about what material will be covered and the order in which this material will be presented. They are valuable because they help improve the clarity of the document and keep the reader on track with the flow of information. Previews are used in two main places: in the introduction following the statement of the writer's purpose, and between the main sections of the formation before driving in nearby sections.
Internal Summaries
Internal summaries are used in the body of a document to review important information already covered before moving on to new information. They provide a summary of the material that the work has already described and thus help the reader to remember the import information before more material is introduced. This allows the reader to "catch" the mind, and connects previously covered sections with the next sections.
Internal summaries are most effective when used in two places: (a) at the end of each major section of the document when much technical or complicated information has been covered; or (b) after the second main section when the paper is divided into three or more major sections. For example, if a document was divided into five main parts, an internal summary would be effective after the third section. If a document was divided into seven main parts, an internal summary would be effective after the fourth or fifth main section.