--- contain logic that allows them to keep traffic for network segments separate.

Bridges.

--- provide links between 2 same-type LANs and are most active at the --- layer.

Routers

Network.

2 ways to prevent looping are ---

1. spanning tree algorithm.

2. source routing (where the source of a packet defines the path).

A bridge reads a packet’s destination address then --- and ---.

Compares it to a routing table and forwards a regenerated signal only to the right segment.

Says Mr Bridge: “You want the dining room? Turn left. You want to leave here? <ignore>”

A gateway is generally (hardware/software).

And what does it modify?

Software – it may modify only the header & trailer of a packet, or the data rate, size and format as well.

Advantages of routers having no memory?

And disadvantages, if any?

Routers have minimal logic.

Frames have minimal control info.

Best routing can be kept current.

Looping/bouncing potential (how? If one table is updated before another table is…)

At what point are counters decremented?

At routers.

Bridges use addressing protocols for flow control inside a LAN; they’re most active at --- layer

Data link.

Data rates can vary between different protocols. So what’s a bridge to do??

Buffer the frame to compensate, so you don’t lose data.

Distinguish between hop-count routing and the symbolic length of a link.

Symbolic approach creates an index number (which is assigned to ---*) that is an assessment of the link’s efficiency, and can include speed, traffic congestion, and the link medium.

*Note: the value is assigned to the link.

Gateways potentially operate in how many layers of the OSI model?

All 7.

Gateways provide --- services between incompatible LANs or apps and are active in --- layers.

Translation

All.

How does a transparent bridge build its table?

It relays the packet to all stations, if it doesn’t know the destination address. Thus low maintenance.

How many different types of bridges can you think of?

(The bridge over the River Kwai doesn’t count!)

Get bonus points for describing them as you go.

Simple (between 2 segments. Has a manually-entered, maintenance-costly address table with pass/no pass logic).

Multi-port (3+ LANs, thus 3+ tables).

Transparent (or learning). Clever girl, she builds her table herself!

Source routing.

How many protocols can a b-router handle?

Brouters can be single or multiple brouters.

I want to install a traffic control device that can determine the best path between source & a destination that may or may not be in the same network. You’d recommend a ---

Router, because it can determine the best next relay point – even for destination nodes in remote networks.

If a single protocol brouter receives a packet belonging to one of the protocols for which is it designed, it routes the packet based on ---; otherwise it acts as a bridge and passes the packet using the ---.

Based on the network layer address.

Using the data link layer address.

Linking a number of LANs into a network requires internetworking devices called ---

Routers and gateways.

List connecting devices by cost, cheapest first.

Repeaters, bridges ; routers, gateways.

RB ; RG

Multi-protocol routers. Name some different protocols they might handle.

IP, IPX, …

Noise can alter the precision of a bit’s --- without destroying its ---. If a corrupted bit travels any further, accumulated noise can ---

Voltage

Identity.

Change its meaning entirely.

Repeaters (or ---) act at the --- layer.

Regenerators, physical.

Repeaters. Describe what they do.

Regenerate the original pattern, then put the refreshed copy back onto the link.

Routing that is dynamically decided is ---

Called adaptive routing.

Solution to looping?

TTL (packet lifetime) that decrements a counter.

Spanning tree algorithm. What is it? And why? And where would you go to buy one?

Bridges are installed redundantly which can cause transparent bridges to loop. The algorithm avoids this. Not sure how!

T/False? A front gate is a protocol converter.

F. It’s a gateway, you silly sausage!

T/False? A repeater amplifies the signal.

F. It generates it, bit for bit, at the original strength.

T/False? Bridges divide a large network into smaller segments.

T.

T/False? Interconnecting devices work in all the layers below their main operating layer.

T.

T/False? Repeater has intelligence.

F.

T/False? Routers “belong to” 2+ networks.

T.

T/False? Routers have no memory.

T.

T/False? You can isolate problem links and securely partition traffic by using a bridge.

T.

The main problem caused by looping is (Lost packets? Congestion? Something else?)

Congestion. Lost packets are regenerated by the data link functions of the source.

What is non-adaptive routing?

When the route doesn’t change according to conditions or topology.

What relays packets among multiple interconnected networks?

Routers do!

(You knew that, didn’t ya? This isn’t hard!)

What’s the difference between least cost routing, cheapest routing & shortest routing?

None. Except that shortest can mean fewest hops (or relays) OR fastest or cheapest or most reliable or most secure.

When a multi-protocol brouter receives a packet belonging to one of the protocols for which is it designed, it routes the packet based on ---; otherwise it acts as a bridge and passes the packet using the ---.

Based on the network layer address.

Using the data link layer address.

Where do you install a repeater?

Before 1 and 0 both look the same, ie. where “attenuation endangers the data integrity,” ie. before signal legibility is lost.

Which of these are used in networking (as opposed to internetworking)?

Bridges, gateways, repeaters, routers

Repeaters and bridges.

(The other 2 are used in internetworking.)

Switch. It’s basically a more efficient ---

Bridge.

Switches have buffers for each ---

And how are buffers used?

Link (network) they’re connected to.

Incoming packets are stored in the buffer of the receiving link, the destination address is checked, and if the outgoing link is free (ie, no chance of ---*) the switch sends the frame to that link.

* collision.

2 types of switch construction are ---

And what’s the difference, eh?

Store and forward – which stores it till the whole frame has arrived.

A cut-through buffer forwards the packet as soon as the destination address is received.

Where does a store and forward switch store the arriving frame?

In the input buffer.

Routing switches are new. They combine a

--- and a ---.

They use what to find the output link, and are faster because ---

Router and a bridge.

Network layer destination address.

Because a regular router only finds the network address of the next *station*.