4. HUB
Ethernet hub, active hub, network hub, repeater hub, multiport repeater or hub is a device
for connecting multiple Ethernet devices together and making them act as a single network
segment. It has multipleinput/output (I/O) ports, in which a signal introduced at the input of
any port appears at the output of every port except the original incoming. A hub works at
the physical layer (layer 1) of the OSI model. Repeater hubs also participate in collision
detection, forwarding a jam signal to all ports if it detects a collision.
Some hubs may also come with a BNC and/or Attachment Unit Interface (AUI) connector to
allow connection to legacy 10BASE2 or 10BASE5 network segments. The availability of low-
priced network switches has largely rendered hubs obsolete but they are still seen in 20th
century installations and more specialized applications.
6. A modem (modulator-demodulator) is a device that modulates an analog carrier
signal to encode digital information anddemodulates the signal to decode the
transmitted information. The goal is to produce a signal that can be transmitted
easily and decoded to reproduce the original digital data. Modems can be used with
any means of transmitting analog signals, from light emitting diodes to radio. A
common type of modem is one that turns the digital data of a computer into
modulated electrical signal for transmission over telephone lines and demodulated
by another modem at the receiver side to recover the digital data.
Modem
7. เราเตอร์
เราเตอร์ (อังกฤษ: router) เป็นอุปกรณ์คอมพิวเตอร์ที่ทา
หน้าที่หาเส้นทางและส่ง(forward)แพ็กเกตข้อมูลระหว่าง
เครือข่ายคอมพิวเตอร์ไปยังเครือข่ายปลายทางที่ต้องการ เรา
เตอร์ทางานบนเลเยอร์ที่ 3 ตามมาตรฐานของ OSI Model
8. A router is a device that forwards data packets between computer networks. This
creates an overlay internetwork, as a router is connected to two or more data lines
from different networks. When a data packet comes in one of the lines, the router
reads the address information in the packet to determine its ultimate destination.
Then, using information in its routing table or routing policy, it directs the packet
to the next network on its journey. Routers perform the "traffic directing" functions
on the Internet. A data packet is typically forwarded from one router to another
through the networks that constitute the internetwork until it reaches its
destination node.
router
