Networking 5-7

Ethernet uses a contention-based ______________________ defined by the IEEE 802.3 standards called Carrier Sense, Multiple Access/Collision Detection (CSMA/CD). Devices use the following process to send data:

Media Access Method

Transmission Media: Ethernet supports the following cable types: • Fiber optic cables, most commonly used in _____________________________, such as servers or streaming media.

high-speed applications

3. The sending ________________ the frame.

host transmits

2. The ________________ the frame and sends it to every host connected to the hub.

hub duplicates

9. The ______________________________ the frame and checks the destination IP address contained in the packet.

last router in the path receives

• While most bridges can process only a single frame at a time, switches can process ________________ simultaneously. • Switches offer guaranteed bandwidth to each switch port.

multiple frames

A switch is a ________________ that performs filtering based on MAC addresses, in addition to providing additional features not found in a bridge.

multiport bridge

4. The _______________ reads the destination MAC address in the frame. Because the frame is addressed to that router, it processes the frame.

next hop router

8. The _________________________________ as necessary, until the frame arrives at the last router in the path.

next hop router repeats steps 4 through 7

5. The router strips off the frame header and examines the ____________________________. It uses the routing table to identify the next hop router in the path.

packet destination address

• Unmanaged switches are autonomous in their function, requiring no port management or configuration. Managed switches allow administrators to change the ______________________, including the following: o Port speed o Duplexing o Filters based on network adapter MAC addresses o VLAN assignment

port configurations

7. The ______________ transmits the frame.

router

6. The ________________ the packet into a new frame. It uses its own MAC address as the source Physical layer address and the MAC address of the next hop router as the destination Physical layer address.

router repackages

Note the following: • A ___________________________________ specified at the Network layer to forward messages to the appropriate network segment.

router uses the logical network address

o If the destination address is in the database, the frame is forwarded to the appropriate segment if the _______________________________ on which it was received.

segment is different from the one

• All _______________________________ are on the same subnet and share a common subnet address.

segments connected to a bridge

• Bridges can connect two segments that use different types of network architecture. For example, a bridge can connect a segment using Ethernet to a segment using __________________.

802.11 wireless

Wireless Access Point (AP): • An _________________; it can read the Data Link layer address in a frame.

AP is a Layer 2 device

Full-duplex • Collision detection is turned off. • The device can send and receive at the same time. • Requires full-duplex capable NICs. • Requires switches with dedicated switch ports (a single device per port).

Bandwidth: Double the rated bandwidth (20 Mbps for 10BaseT, 200 Mbps for 100BaseT, etc.)

Half-duplex • Collision detection is turned on. • The device can send or receive in only one direction at a time. • Devices connected to a hub must use half-duplex communication.

Bandwidth: Up to the rated bandwidth (10 Mbps for 10BaseT, 100 Mbps for 100BaseT, etc.)

• _________________________; they read the MAC address contained in a frame to make forwarding decisions.

Bridges are Layer 2 devices

• _____________________________; they read the MAC address contained in a frame to make forwarding decisions.

Bridges are Layer 2 devices

o _______________ are forwarded to all segments except the one on which they were received. You should be aware of the following regarding bridges:

Broadcast frames

These frames include a ____________________, which is used to detect frames that have been corrupted during transmission. Hosts use the Reverse Address Resolution Protocol (RARP) to find the IP address of a host with a known MAC address.

Cyclic Redundancy Check (CRC)

Note the following: • ______________ addresses in the frame change as the frame is delivered from hop to hop. At any point in the process, the ________________ destination address indicates the physical address of the next hop on the route. The _____ source address is the physical address of the device sending the frame.

Data Link

Note the following: • Both _____________________________ and Network layer logical addresses are used to send packets between hosts on different subnets.

Data Link layer physical addresses

Physical Addresses

Ethernet devices are identified by using the MAC address, which is burned into the network interface card.

• _____________________ the type of traffic allowed into a network and the type of traffic allowed out of a network.

Firewall rules control

If the MAC address isn't known, ARP does the following to find it: 1. The sending device sends out a broadcast frame. o The destination MAC address is all________________. o The sending MAC address is its own MAC address. o The destination IP address is the known IP address of the destination host. o The sending IP address is its own IP address.

Fs (FFFF:FFFF:FFFF)

• Collision detection is turned off.

Full-duplex

• Requires full-duplex capable NICs.

Full-duplex

• Requires switches with dedicated switch ports (a single device per port).

Full-duplex

• The device can send and receive at the same time.

Full-duplex

• Devices connected to a hub must use half-duplex communication.

Half-duplex

3. The host to which the frame is addressed accepts the frame. Every other host ignores the frame. _____________________; they simply repeat incoming frames without examining the MAC address in the frame.

Hubs are Layer 1 devices

Note the following: • _____________________ are contained in the IP header; MAC (Data Link layer) addresses are contained in the Ethernet frame header.

IP (Network layer) addresses

3. If the destination_____________ its own address, the host responds with a frame that includes its own MAC address as the sending MAC address.

IP address matches

To send a message from one host to another on a different network, the following process is used: 1. The sending host prepares a packet to be sent. It uses its own IP address as the source Network layer address and the __________________________ device as the destination Network layer address.

IP address of the final receiving

Devices like hubs, switches, and bridges connect multiple devices to the same network segment. _______________________ devices connect multiple networks or subnets together and enable communication between hosts on different types of networks. The following table lists several common ___________ devices:

Internetwork

A ______________ is capable of reading Layer 3 (network) addresses and routing packets between subnets.

Layer 3 switch

A bridge builds a database based on MAC addresses to make forwarding decisions: • The process begins by examining the source_________________of an incoming frame. If the source address is not in the forwarding database, an entry for the address is made in the database, associating the MAC address with the media segment.

MAC address

To send a message from one host to another on a different network, the following process is used: 2. The sending host creates a frame by adding its own __________________________________________. For the destination Physical layer address, it uses the MAC address of the default gateway router.

MAC address as the source Physical layer address

4. The original sender reads the MAC address from the frame and associates the IP address with the MAC address, saving it in its cache. Once the sender knows the _________________________, it sends data in frames addressed to the destination device.

MAC address of the receiver

The ________________ indicate the logical address of the original sending device and the address of the final destination device.

Network addresses

Each of the devices listed in this table operates at the _________________________________ of the OSI model. Some firewalls are also capable of operating at higher layers and make filtering decisions based upon information found in the upper OSI model layers.

Network layer (Layer 3)

Devices used on Ethernet networks include: • NICs • Hubs (obsolete) • Switches • Routers

Networking Devices

______________________ about other networks in a database called a routing table. The routing table typically contains the address of all known networks and the next router in the path used to reach the destination network. It is used in the process of forwarding packets.

Routers maintain information

_______________, read their headers to find addressing information, and send them on to their correct destination on the network or Internet.

Routers receive packets

Ethernet uses the following networking topologies, depending upon the specification being implemented: Physical & Logical

Topology:

star

Topology: • Physical _____, logical _____

logical

Topology: • Physical star, __________ bus

Physical

Topology: • ___________ bus, logical bus

Ethernet supports the following cable types: • Unshielded twisted pair (UTP) cables with RJ45 connectors. This is the most common _______________________ used for Ethernet. • Fiber optic cables, most commonly used in high-speed applications, such as servers or streaming media. • Coaxial cables for older Ethernet implementations (often called thinnet or thicknet networks).

Transmission Media

A Layer 3 switch often provides better performance than ________, but it does not support as many features as a router.

a router

• The ______ is often written as 00-B0-D0-06-BC-AC or 00B0.D006.BCAC (dashes, periods, and colons can be used to divide the MAC address parts).

address

• The destination address is then examined: o If the destination ______________________, the frame is sent out on all segments except for the one on which it was received.

address is not in the database

• The destination _________________________: o If the destination address is not in the database, the frame is sent out on all segments except for the one on which it was received.

address is then examined

Media Access Method: • Because _____________________________ (multiple access) to the transmission media, a device listens to the transmission medium to determine if it is free before sending data (carrier sense).

all devices have equal access

o If the destination address is in the database, the frame is forwarded to the _______________ if the segment is different from the one on which it was received.

appropriate segment

Ethernet is the most popular networking _______________________________. It offers high performance at a low cost and is easy to install and manage. The following table describes various details about Ethernet:

architecture for LANs

Media Access Method: • Both devices wait a random length of time before ____________________ message (backoff).

attempting to resend the original

2. All hosts on the subnet process the _______________, looking at the destination IP address.

broadcast frame

A hub is the ____________________________, logical bus topology. Hubs manage communication among hosts using the following method: 1. A host sends a frame to another host through the hub. 2. The hub duplicates the frame and sends it to every host connected to the hub. 3. The host to which the frame is addressed accepts the frame. Every other host ignores the frame. Hubs are Layer 1 devices; they simply repeat incoming frames without examining the MAC address in the frame.

central connecting point of a physical star

• All segments connected to a bridge are on the same subnet and share a ______________________.

common subnet address

Wireless Access Point (AP): • An AP is often __________________, connecting a wireless segment to a wired segment. Both wireless and wired hosts are on the same subnet.

configured as a bridge

• Routers can be used to __________________________ (e.g., connecting an Ethernet network to a Token Ring network).

connect networks with different architectures

• Routers can be used to _______________________, or they can be used as gateways to connect multiple LANs together.

connect subnets within a single LAN

• The process begins by examining the source MAC address of an incoming frame. If the source address is not in the forwarding database, an entry for the address is made in the ___________________ with the media segment. • The destination address is then examined:

database, associating the MAC address

• Network addresses remain constant as the packet is ____________________.

delivered from hop to hop

Media Access Method: • If two devices transmit at the same time, a collision occurs. The sending devices ____________________________ and send a jam signal to notify all other hosts that a collision has occurred.

detect the collision (collision detection)

12. The destination ______________________. Inside the packet it finds that the destination Network layer address matches its own IP address, and the source IP address is that of the original sending device.

device receives the frame

10. Because the destination device is on a ___________________________, the router creates a frame using its own MAC address as the source Physical layer address, and the MAC address of the destination device as the destination Physical layer address.

directly connected network

• The MAC address is a 12-digit (48-bit) hexadecimal number (__________________________________).

each number ranges from 0-9 or A-F

• Bridges are used to separate one part of a subnet from another. This _________________________ between segments and keeps the network from wasting bandwidth.

eliminates unnecessary traffic

A bridge is a device that connects two (or more) media segments on the same subnet, and it _______________ between both segments based on the MAC address in the frame.

filters traffic

A bridge is a device that connects two (or more) media segments on the same subnet, and it ___________________________________ based on the MAC address in the frame. A bridge builds a database based on MAC addresses to make forwarding decisions:

filters traffic between both segments

• The MAC address is globally unique by design. The _______________ of the MAC address is assigned to each manufacturer. The manufacturer determines the rest of the address, assigning a unique value that identifies the host address. A manufacturer that uses all the addresses in the original assignment can apply for a new MAC address assignment.

first half (first 6 digits)

A firewall is a router with additional security features. Firewalls can be programmed with security rules to restrict the _________________________.

flow of traffic between networks

o Broadcast frames are ________________________ except the one on which they were received. You should be aware of the following regarding bridges:

forwarded to all segments

A _______ is a unit of data that is ready to be sent on the network medium. Ethernet frames contain the following components:

frame

Devices with collision detection turned on operate in ________________________; devices with collision detection turned off operate in full-duplex mode.

half-duplex mode

• A firewall can be either _______________________ installed onto operating systems.

hardware devices or software

• Devices use the MAC address to send frames to other devices on the same _____________. Some network cards allow you to change the MAC address through jumpers, switches, or software. However, there are few legitimate reasons for doing so.

subnet

A router is a device that connects two or more network segments or ___________. • Each ____________ has a unique, logical network address.

subnets

• Switches can make additional forwarding decisions based on the MAC address. For example, a ___________________________frames from specific MAC addresses. • Like bridges, switches operate at Layer 2.

switch can be configured to accept

Transmission Media: Ethernet supports the following cable types: • Coaxial cables for older Ethernet implementations (often called ___________________).

thinnet or thicknet networks

Media Access Method: • If it is not free, the device waits a random amount of time and listens again to the ________________________. If it is free, the device transmits its message.

transmission medium

11. The router_________________.

transmits the frame

Transmission Media: Ethernet supports the following cable types: • Unshielded __________________ with RJ45 connectors. This is the most common transmission medium used for Ethernet.

twisted pair (UTP) cables

Address Resolution Protocol (ARP) ARP is used by hosts to discover the MAC address of a device from its IP address. Before _________________, they must know the MAC address of the receiving device.

two devices can communicate

• Bridges can connect two segments that use different _______________________. For example, a bridge can connect a segment using Ethernet to a segment using 802.11 wireless.

types of network architecture

MAC Address: A MAC address is a ___________________________ into the ROM of every Ethernet NIC.

unique identifier burned

• Bridges are used to separate one part of a subnet from another. This eliminates _______________________ and keeps the network from wasting bandwidth.

unnecessary traffic between segments

• Frame forwarding happens independently of the ___________________________.

upper-layer protocols (such as TCP/IP)

• Frame forwarding happens independently of the ________________________________.

upper-layer protocols (such as TCP/IP)

Wireless Access Point (AP): • Some APs are combination devices that include a _____________ and even a router.

wired switch

A ________________________ is a hub for a wireless network. • Like with a hub, any message sent to any wireless host connected to the AP can be received by all other wireless hosts.

wireless access point (AP)

Half-duplex

• Collision detection is turned on.

Half-duplex

• The device can send or receive in only one direction at a time.