Internetworking hardware: Bridging Flashcards
What are local bridges?
Provide direct connection between multiple LAN segments in same area
What are remote bridges?
- connect multiple LANs in different areas, often over telecom lines
What are some challenges and solutions for remote bridges?
- LAN speeds generally > WAN speeds
- buffering can compensate for discrepancies
What are collision domains?
- way that bridges segment traffic on a network
- small cluster of stations on a network that share bandwidth
- make LANs more manageable and reduce congestion
- traffic does not cross domains unless addressed to go there
Are bridges used today?
Only on legacy networks.
Today: routers using tunnelling technology with Layer 3 devices
Networks with hubs may use Layer 3 switches instead.
Name 4 types of internet working devices.
Switches, routers, bridges, gateways
Describe switches and applicable OSI layer.
Most elementary type of device to connect 2 networks. Opens/closes switches. Layers 1 and 2.
Describe routers and name applicable OSI layers.
Interface between 2 networks; recognize protocols and node addressed; more expensive and intelligent than switches, but also slower.
Layers 1, 2, 3
Describe bridges and name associated OSI layers.
- Connect 2+ network segments and forward info between them
- operate at layer 1; can also connect disparate LANs at layers 1 and 2
What were old vs new bridges?
Old: 2 NICs in one PC running special software
New: different protocols bridges together through bridges; data forward between networks
Describe what gateways do and name associated OSI layers.
- connect unlike networks (different architectures and environments) and can repackage info
- provide mapping at all 7 layers
- different gateways are dedicated to each type of transfer due to forwarding complexity
What does a bridge do when it recognizes or does not recognize the MAC address in a packet?
Knows: forwards
Doesn’t know: broadcasts to all ports but the one it received the packet from
Name three link layer control functions that bridges perform.
- flow control
- error handling
- physical addressing
What is the difference between transparent bridging and source-rate bridging?
Transparent: frames are forwarded one at a time
Source-rate: entire path is contained in each frame
What is spanning tree protocol?
A protocol that enables Ethernet networks to achieve some redundancy in the network, but to limit loops between bridges, which can result in a data storm.
Bridges transmit PDUs to find other bridges in the network and build a tree, from which they can enable or disable links.
What type of bridge links two dissimilar networks?
Translating bridge.
What are the two most important functions that bridges perform?
Filtering and flooding
What is filtering?
A bridge looks at data link layer fields and blocks any that should not be forwarded, thereby reducing congestion.
What is flooding?
Broadcasting information out of all ports on the bridge or to all ports on an associated switch.
