3'1'6 Internetwork Connection Equipment

1
3.1.6 Internetwork Connection Equipment
Interconnection
2
Basic Network Connection devices
Relay equipment
Router
Bridge Switching Hub
Repeater HUB
3
Internetwork Connection Equipment

• 1. Repeater
• The main function of a repeater is to extend the
  physical distance of a LAN segment.
• Perform relay functions on the physical layer
• LAN system connected by a repeater can logically
  be regarded as one LAN
• Only recognized data as electrical signals (bit
  strings)

4
Repeater located in the first layer of the OSI
RM, and extend LAN physically
-Characteristics- Physical extension of
LAN Transmission line can be extended
Data
Relay function
Repeater
Data
Hub
5
Repeater Hub (Conventional hub)
Data to B
Data to B
Data to B
Data to B
A
B
C
D
Repeater HUB simply rebroadcast every packet
every port. All terminals cant communicate at
the same time. (share the transmission path)
6
HUB Connection
1. Cascade Connection
2. Stack Connection
UTP Cable
Stack Cable (by Vendors)
Treats as a HUB
7
handling instruction
10 mbps Repeater HUB
1
2
Addition
1
2
3
4
Cascading is up to 4
4
3
8

• Advantages of using repeaters.
• A repeater can connect one segment of a LAN to
  another, possibly connecting different types of
  media. For example, a repeater can connect thin
  Ethernet cables to unshielded twisted pair (UTP)
  Ethernet cables.
• Repeaters are fast, simple to use, and
  inexpensive.
• Repeaters can be used to attach "link segments"
  to extend the overall distance of a network,
  subject to the Ethernet "5/4/3 rule."

9

• Disadvantages to using Repeaters
• Because it is only a signal-boosting device,
  working at the Physical Layer, a repeater cannot
  connect two different media access types (Data
  Link protocols) such as Token Ring and Ethernet.
  
• Repeaters are feasible only for relatively small
  LANs (less than 100 nodes), confined to a small
  geographical area such as one or two floors of an
  office building. A repeater should not be used to
  connect heavily used LANs, because it cannot
  isolate traffic between LAN segments. Therefore,
  if we connect multiple LAN segments using a
  repeater, we may experience performance problems,
  because total network traffic will increase.

10
Internetwork Connection Equipment

• 2. Bridge
• Perform relay functions on the data link layer
• Logical bridges for direct connection of LAN
  systems
• Remote bridges for connection of LAN system via
  communication lines (leased lines)
• Recognized data as one piece of data (packet)

11
Bridge located in the second layer of the OSI
RM Data is relay by using the MAC address
Data forwarding is judged by MAC
address Unnecessary data is not transmitted to
other segments
Data
Bridge
Only necessary data is relayed!!
12
Bridge Functions
13

• There are several advantages to using bridges.
• To isolate traffic between LAN segments that have
  nodes that only occasionally send traffic across
  the bridge. Bridges divide a network into
  separate collision domains, because they use NIC
  addresses to filter or forward traffic between
  different network segments.
• Bridges are simple to install. To use advanced
  bridging features, such as custom filters, a
  minimal amount of configuration is required. The
  presence of a bridge is transparent to users from
  the instant it is first installed, and bridges
  adapt automatically to network changes.
  Bridge-based internetworks can be modified and
  reconfigured very easily.

14

• Bridges can connect networks running different
  high-level protocols, without requiring
  additional software. They operate at the Data
  Link Layer of the OSI model network managers do
  not need to know in advance which high-level
  protocols will be used.
• Some protocols are simply unroutable, such as
  Digital Equipment Corporation's (DEC's) Local
  Area Transport (DEC-LAT) terminal communications
  protocol, IBM's Systems Network Architecture
  (SNA), and network basic input/output system
  (NetBIOS)/NetBios Enhanced User Interface
  (NETBEUI). Unroutable protocols must be bridged.
• Bridges form logically single networks. All
  interconnected network segments have the same
  network identifier we can move end stations
  without configuring new network addresses for
  them.

15

• Several disadvantages of using bridges
• There is a limit to the size of bridge-based
  networks. Each time a frame traverses a bridge it
  is delayed as the bridge software reads the
  source and destination addresses, checks its
  address database, and determines whether to
  forward the frame to each port. If the frame
  crosses many bridges, this frame latency may
  cause the destination station to time out and
  request retransmission. This would result in an
  unnecessary duplication of frame transmissions.
• While network segments attached to a bridge
  belong to different collision domains, they all
  belong to the same broadcast domain. This is
  because bridges allow broadcast frames to flood
  the network. Bridges themselves also create
  broadcast traffic that congests the network, as
  they attempt to resolve unknown destination NIC
  addresses.

16

• Several disadvantages of using bridges
• Bridges cannot prevent broadcast storms that may
  occur when certain broadcast protocols cause
  frames to be flooded to every port. If there is a
  malfunction or an incorrectly configured
  parameter, these traffic spikes can be severe
  enough to disable the entire network.
• Bridges cannot take simultaneous advantage of
  redundant paths in a network. They cannot
  load-split over network segments.
• Bridges cannot convert protocols above the Data
  Link Layer.

17
When to Use Bridges

• Bridges should control segment or workgroup
  access to the backbone, because an overloaded
  backbone puts all organization communications in
  danger. If we connect only internetworking
  devices and a few large servers directly to the
  backbone, we will reduce the number of
  application, hardware, and other errors that
  affect the backbone.

18
Internetwork Connection Equipment

• 3. Router
• Perform relay functions on the network layer
• Interconnect between different networks
• Data passes only to the specified party
• The router identifies the address (IP address) of
  the data and select the route along which the
  data will travel
• Reduce traffic load and provide security

19
Router Third layer of the OSI RM Network
address is used for the path control (routing)
Network A
Data is relayed by the network address Identify
the protocol
Router 3
Router 1
Router
Network B
Router 2
Network C
20
Routing
Routing table of router 1
Routing table of router 2
192.168.5.2
192.168.5.1
192.168.2.1
Router 1
Router 2
192.168.1.1
192.168.3.1
192.168.2.1
192.168.4.1
B
A
192.168.1.0
192.168.2.0
192.168.3.0
192.168.4.0
A direct routing
B indirect routing
21

• Routers offer several advantages
• A router provides a firewall service, because it
  forwards only traffic specifically addressed to
  go across the router. This eliminates the
  possibility of broadcast storm propagation, the
  transmission of frames from unsupported
  protocols, and the transmission of frames
  destined for unknown networks across the router.
  Routers keep potentially disastrous events local
  to the area in which they occur, preventing them
  from spreading across the corporate network.
• The enhanced intelligence of a router allows it
  to support redundant network paths, and select
  the best forwarding path based on several factors
  in addition to the destination MAC address. This
  increased intelligence can also result in
  enhanced data security, improved bandwidth
  utilization, and more control over network
  operations.

22
Routers offer several advantages-cont.

• Routers are the only internetworking devices that
  can provide efficient WAN access. Because routers
  do not forward broadcast traffic, they help
  control the traffic load on small, expensive WAN
  pipes. Routers offer access to a wide variety of
  WAN technologies, allowing network managers to
  select the best economic value for their
  networking needs. Router-based techniques such as
  data compression, traffic prioritization, and
  packet spoofing also help make efficient use of
  WAN bandwidth.
• Routers can flexibly integrate disparate Data
  Link Layer technologies, such as Ethernet, Fast
  Ethernet, Token Ring, FDDI, and ATM. They can
  also consolidate legacy IBM mainframe networks
  with personal computer (PC)-based networks
  through the use of Data Link Switching (DLSw).

23

• Disadvantages of Routers
• The additional software processing performed by a
  router can increase packet latency, reducing the
  router's performance when compared to simpler
  switch architecture.
• To be "routable," an architecture must have a
  Network Layer. Not all do those protocols must
  be bridged. "Unroutable" protocols include
  DEC-LAT terminal communications protocol, IBM's
  SNA, and NetBIOS/NETBEUI.

24
When to Use Routers

• Routers are needed when network applications
  require limiting broadcast traffic, support for
  redundant paths, intelligent packet forwarding,
  or WAN access. If the application requires only
  increased bandwidth to ease a traffic bottleneck,
  a switch is likely the better choice. The
  technology choices appropriate for a specific
  workgroup, department, or building backbone
  depend upon the organization's business and
  technical requirements.

25
Bridge vs. Router
26
Internetwork Connection Equipment

• 4. Gateway (network conversion)
• also called a protocol converter, converts data
  between two distinct types of protocol
  architectures. A gateway operates at all protocol
  levels above the Data Link Layer, and is
  transparent to both ends of the connection.
• Use to establish interconnection between an OSI
  network and a TCP/IP network

27

• The advantages of a gateway
• A gateway is the only internetworking device that
  can change the form of a network transmission
  from that of one communications architecture to
  that of another. For example, a gateway can
  connect a Transmission Control Protocol/Internet
  Protocol (TCP/IP) network to an SNA network.
  Another example of a gateway is a node that
  converts OSI Message-Oriented Text Interchange
  System (MOTIS) mail to Simple Mail Transfer
  Protocol (SMTP) for TCP/IP delivery.

28
(No Transcript)
29

• Disadvantages of gateways
• Protocol conversion is a software-intensive
  (slow) process, different for each specific pair
  of protocol stacks. A gateway receives frames
  from one communications architecture, and must
  convert them to another architecture by building
  new headers for every layer of the protocol
  stack.

30
When to Use Gateways

• Gateways are necessary to connect any two
  networks that use different communications
  architectures. For example, we must use a gateway
  to convert electronic mail (e-mail) as it moves
  between SNA and TCP/IP environments.

31
Networks Speed-up Technology

• 4. Switching Hub
• A switch is a device that consists of many
  high-speed ports connecting either LAN segments
  or individual devices on a port-by-port basis.
• Ethernet switch
• Token ring switch
• Data is switched to the destination terminal as
  the MAC address of the data id identified inside
  the switching hub

32
Switching HUB
Data to B
Data to B
Data to B
Data to B
A
B
C
D
Switching hubs forward each packet only to the
required port referring to MAC address in the
received data. Possible to communicate between
two or more terminals simultaneously.
33
Fast Ethernet
Optic-fiber Cable
HUB
HUB
100 BASE-FX
Port for 100BASE-TX
100 BASE-TX
100 BASE-TX
UTP (Cat.5), STP
100 BASE-TX
NIC for 100BASE-TX
34

• Many types of switches exist, each supporting
  different speeds and LAN types such as Ethernet,
  Token Ring, Fiber Distributed Data Interface
  (FDDI), and Asynchronous Transfer Mode (ATM). A
  switch dedicates the entire LAN media bandwidth
  (such as 10-Mbps Ethernet) to each port-to-port
  frame transmission. In this way, a switch
  multiplies the amount of effective network
  bandwidth.
• When a frame sent by Node A destined for Node E,
  the switch routes the frame between Port 1 and
  Port 3. In this case, Port 3 and Port 4 will
  still be free to send frames at a full 10 Mbps
  rate. If Node A sends a frame to Node B, the
  switch restricts the frame to the individual
  segment that contains both Node A and Node B.
  Switches therefore maximize overall network
  bandwidth by creating virtual circuits on a per
  frame basis.

35
(No Transcript)
36

• Switches offer several advantages
• Switches segment a network into smaller collision
  domains, providing a larger share of the
  available bandwidth to each end station. Their
  protocol transparency allows them to be installed
  in networks running multiple protocols with
  little or no software configuration.
• Switches are totally transparent to end stations.
  They use existing cabling, repeaters/hubs, and
  end station adapters without expensive hardware
  upgrades.

37

• Disadvantages of Switches
• Network segments attached to a switch belong to
  different collision domains however, they all
  belong to the same broadcast domain because
  switches allow broadcast frames to flood the
  network.
• Switches also create broadcast traffic that
  congests the network, as they attempt to resolve
  unknown destination NIC addresses.

38
When to Use Switches

• A switch is a special-purpose device specifically
  designed to address LAN performance problems
  resulting from bandwidth shortages and network
  bottlenecks. A switch economically segments a
  network into smaller collision domains (in the
  case of Ethernet), providing a higher percentage
  of bandwidth to each end station.
• Switches are not designed with the principal goal
  of providing control over a network. Switches
  should be viewed as bandwidth providers, not as
  sources of security, redundancy, control, or
  network management.

39
Thats all folks