Drops, Hubs, Switches, and
Router
Drops
 A drop is a way of connecting a computer to
an Ethernet.
 A drop is a splice into an Ethernet cable.
 A computer on a drop can “see” all traffic
coming across the Ethernet cable.
Drop
Drops
 Security concerns with drops:

The computer on the drop can monitor all
traffic on the main line.
Hubs
 When a hub receives a packet of data at one of
its ports from a PC on the network, it transmits
(repeats) the packet to all of its ports and, thus,
to all of the other PCs on the network.
Each computer on a hub can “see” the other computers data.
Hubs
 If two or more PCs on the network try to send
packets at the same time a collision is said to
occur.
 When that happens all of the PCs have to go
though a routine to resolve the conflict.
 The process is prescribed in the Ethernet
Carrier Sense Multiple Access with Collision
Detection (CSMA/CD) protocol.
Hubs
 Each Ethernet Adapter card on a computer
has both a receiver and a transmitter.
 Non point to point connections have to
operate at half duplex.
 The adapters must listen with their receivers
for collisions and cannot receive data at the
same time they are sending it.
 Full duplex Ethernet can be implemented on
point to point connections.
Hubs
 Security concerns with hubs:

A computer on a hub can see all Ethernet
traffic that goes to any computer on that hub.
Switches
 An Ethernet switch:
 Automatically divides the network into multiple
segments,
 Acts as a high-speed, selective bridge
between the segments, and
 Supports simultaneous connections of multiple
pairs of computers which don't compete with
other pairs of computers for network
bandwidth.
Switches
Connections can
“change”
Switches
Switches
 Security concerns with switches:


A computer on a switch can only see the data
that has been addressed to that computer.
This makes switches more secure than hubs
or drops.
Routers
 A router is a more sophisticated network device
than either a switch or a hub.
 Traditional routers are designed to join multiple
area networks.
 Routers can move packets based on IP
addresses and can be used outside of a subnet.
 Hubs and switches move packets based on
MAC addresses and can only be used within a
subnet.
Routers
 On the Internet or on a large corporate network,
for example, routers serve as intermediate
destinations for network traffic.
 These routers receive TCP/IP packets, look
inside each packet to identify the source and
target IP addresses, then forward these packets
as needed to ensure the data reaches its final
destination.
Routers
 Routers for home networks (often called
broadband routers) also can join multiple
networks.
 These routers are designed specifically to join
the home (LAN) to the Internet (WAN) for the
purpose of Internet connection sharing.
Routers
 In contrast, neither hubs nor switches are
capable of joining multiple networks or
sharing an Internet connection.
Routers
 A home network with only hubs and switches
must designate one computer as the gateway
to the Internet, and that device must possess
two network adapters for sharing, one for the
home LAN and one for the Internet WAN.
 This “gateway” computer takes care of
routing information.
 With a router, all home computers connect to
the router equally, and it performs the
equivalent gateway functions.
Routers
 Additionally, broadband routers contain
several features beyond those of traditional
routers.
 Broadband routers provide DHCP server and
proxy support.
 Most of these routers also offer integrated
firewalls.
Routers
 Security with routers:



Most DHCP routers can perform Network
Address translation (NAT).
NAT allows one internet address to be
translated into multiple Internet addresses.
This allows the router to “hide” the actual IP
address of a machine in the Intranet from
outside attacks.
Packet for IP:
141.165.208.049
Port 12121
IP and port are translated to a MAC
address
Internet
IP: 141.165.208.049
Packet is forwarded to the
correct computer on the subnet
WIFI Routers
 In home networking, hubs and switches
technically exist only for wired networks.
 Wi-Fi wireless routers incorporate a built-in
access point that is roughly equivalent to a
wired switch.
Router
Adapter