Module 4.0: Network Components

1
Module 4.0 Network Components

• Repeater
• Hub
• NIC
• Bridges
• Switches
• Routers
• VLANs

2
Hardware Components

• Repeater
• Layer 1 device that provides physical and
  electrical connections.
• It receives signals from one cable segment,
  regenerates, retimes, and amplifies them, and
  then transmits these revitalized signals to
  another cable segment.
• Transmits in both directions
• Joins two segments of cable
• No buffering
• No logical isolation of segments
• Hub
• Used to describe a repeater
• Can be repeater hub, switching hub, bridging
  hub.
• NIC
• Network Interface Card
• Performs layer-2 functions framing, error
  detection, and flow control.
• Performs layer-1 functions by converting the bits
  into electrical signals using appropriate coding
  scheme.

3
Bridges

• Layer 2 devices
• Interconnects two or more individual LANs or LAN
  segments.
• Desirable for separating traffic among segments.
  A segment is part of a LAN in which traffic is
  common to all nodes, i.e. it is a single
  continuous conductor, though it may include
  repeaters.
• Can be used to connect different speeds/physical
  layer types of networks together (10BaseT to
  100Base F)
• Split the segment with bridges/switches, if link
  utilization is more than 30.
• Store-and-forward devices. They capture the
  entire frame before deciding whether to filter or
  forward it. Frames with bad CRC are not
  forwarded.
• Minimal buffering to meet peak demand

4
Switches

• Switches can operate at different layers layer
  2, 3, 4, and 7..
• Basically a switch is hardware based, not
  software based.
• Three types of layer 2 switches
• Store-and-Forward Switch
• Similar to store-and-forward bridge. Store entire
  frame, check for errors, and then switch to the
  other ports, based on the destination MAC
  address.
• Cut-Through Switch
• The transmission of frame begins as soon as it
  reads the destination MAC address. Two switch
  fabric/matrix designs
• Crossbar
• Backplane with bus speed gt aggregate port speeds
• Hybrid Switch
• Reliability store-and-forward. Turn ON when
  errors are high.
• Low latency cut-through. Turn ON when errors are
  low.

5
Routers vs. Switches

• The primary difference is one semantics.
  Switches historically infer CO links routers use
  CL links. Traditionally, routers have performed
  router table lookups and packet forwarding in
  software.
• Layer-2 Switches start having routing
  functionality, and Layer-3 routers start having
  ASIC (Application Specific Integrated Circuit)
  switching technology for packets.
• Layers 2 and 3 are merging and it is becoming
  difficult to distinguish between switches and
  routers.
• Layer 3 or IP switching routing IP packets in
  ASIC, e.g, MPLS.
• Layer 4/7 switching is a new and emerging area,
  called information content switching.
• Layer 4 direct all traffic based on TCP
  destination port.
• All traffic with destination TCP port 80, is
  directed to a switch port where a web cache
  resides.
• Layer 7 direct traffic based on information used
  in the payload.
• Examine URL GET request. If request for image,
  direct it request to an optimized image server
  port.

6
VLANs

• VLAN is a logical grouping of nodes using
  Ethernet switches. Nodes dont need to be
  connected physically to the same switch. A
  broadcast frame will be heard by all nodes within
  VLAN.
• Benefits
• Isolates broadcasts
• Frees up network from physical locations
• Easily shares resources. A server can be part of
  multiple VLANs.
• Performance. Easily can be enhanced by creating
  new VLANs.
• Security. By containing who can listen to
  broadcast.
• VLAN Membership (implicit tagging)
• Port-based
• MAC-based
• Layer 3/IP
• Combination of the above