Term
What does CSMA/CD stand for
and where does it apply? |
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Definition
Carrier Sense Multiple Access / (with) Collision Detection
Applicable on half duplex ports |
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Term
| What happens when a collision occurs over Ethernet (collision domain)? |
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Definition
1. Jam signal sent by hosts involved in collision
2. All hosts involved briefly stop transmitting
3. Hosts each run a backoff algorithm (waits a random time before retransmission) |
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Term
What can break up a collision domain?
What can break up a broadcast domain? |
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Definition
collision domain: switches, bridges, full duplex host connections
broadcast domain: routers, vlan
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Term
Identify the common name, speed and IEEE spec of of the following: 10-BASE 5 10-BASE T 100-BASE T 100-BASE FX 1000-BASE T 1000-BASE SX |
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Definition
10-BASE 5/T : Ethernet, 10Mbs, 802.3 100-BASE T/FX : FastEthernet, 100Mbs, 802.3u 1000-BASE T : GigabitEthernet, 1000Mbs, 802.3ab 1000-BASE SX : GigabitEthernet, 1000 Mbs, 802.3z |
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Term
Identify the duplex, media, and length of the following
10-BASE 5
10-BASE 2
10/100/1000-BASE T
100-BASE FX
1000-BASE ZX |
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Definition
10-BASE 5 : Half, Thicknet, 500 m
10-BASE 2 : Half, Thinnet, 185 m
10-BASE T : Half, UTP, 100 m
100-BASE T : Half/Full, UTP, 100 m
1000-BASE T : Full, UTP, 100 m
100-BASE FX : Full, Multi-mode Optic, 400 m
1000-BASE ZX : Full, Single-mode Optic, 100 km |
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Term
Name the acronym and order the layers of the
OSI Model
Name the type of PDUs used at each layer. |
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Definition
Open Systems Interconnection Model:
7. Application (Data)
6. Presentation (Data)
5. Session (Data)
4. Transport (Segment)
3. Network (Packet)
2. Datalink (Frame)
1. Physical (Bits) |
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Term
Name and order the layers of the TCP/IP Model
(and list the corresponding OSI layers) |
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Definition
4. Application = Application, Presentation, Session
3. Transport = Transport
2. Internet = Network
1. Network Interface = Data Link, Physical |
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Term
Identify the protocol
(full name, OSI layer, port, transport type)
FTP |
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Definition
File Transfer Protocol
Application Layer
TCP port 20, 21 |
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Term
Identify the protocol
(full name, OSI layer, port, transport type)
SMTP |
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Definition
Simple Mail Transfer Protocol
Application Layer
TCP port 25 |
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Term
Identify the protocol
(full name, OSI layer, port, transport type)
POP3 |
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Definition
Post Office Protocol v.3
Application layer
TCP port 110 |
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Term
Identify the protocol
(full name, OSI layer, port, transport type)
NTP |
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Definition
Network Time Protocol
Application layer
UDP port 123 |
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Term
Identify the protocol
(full name, OSI layer, port, transport type)
TFTP |
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Definition
Trivial File Transfer Protocol
Application layer
UDP port 69 |
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Term
Identify the protocol
(full name, OSI layer, port, transport type)
DNS |
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Definition
Domain Naming System
Application layer
By default uses UDP port 53
Fall back to TCP port 53 |
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Term
Identify the protocol
(full name, OSI layer, port, transport type)
DHCP |
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Definition
Dynamic Host Configuration Protocol
Application layer
UDP port 67, 68 |
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Term
| What happens when establishing a TCP connection? |
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Definition
Three-way handshake:
1. A --> B : SYN with seq(A)
2. A <-- B : SYN with seq(B), ACK with seq(A+1)
3. A --> B : ACK with seq(B+1) |
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Term
| What are the 3 main elements of Positive Acknowledgement and Retransmission (PAR) |
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Definition
1. Sender will re-transmit a segment if the timer expires before an ACK
2. Sender has record of all segments waiting ACK
3. Receiver ACKs a segment with the next sequence number expected |
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Term
What is the TCP sliding window? |
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Definition
TCP sliding window is a method for the receiver to negotiate the transmission rate of the sender. Large window = large number of segments sent before ACK'ed. S --> R : X number packets, window size = X S <-- R : ACK of Yth packet, window size = Y S --> R : Y number packets, window size = X |
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Term
| Describe the rough layout of the TCP header |
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Definition
__________________________ [ Source port | Dest. port ] [ Sequence number ] [ Ack number ] [ misc. | win size ] [ checksum | urgent ] [ options ] |
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Term
| Describe the rough layout of the UDP header |
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Definition
_______________________ [ source port | length ] [ dest. port | checksum ] |
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Term
Identify the protocol
(full name, OSI layer, port, transport type)
CDP |
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Definition
Cisco Discovery Protocol
Data Link layer
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Term
Identify the protocol
(full name, OSI layer, port, transport type)
ICMP |
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Definition
Internet Connection Management Protocol
Network layer
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Term
Identify the protocol
(full name, OSI layer, port, transport type)
ARP / RARP |
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Definition
(Reverse) Address Resolution Protocol
Network layer
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Term
What layer (and duplex) do the following device types operate on:
Hubs
Repeaters
Switches
Bridges
Routers |
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Definition
Hubs / Repeaters : L1, half-duplex
Bridges: L2, usually half-duplex
Switches: L2, usually full-duplex
Routers : L3, na (full) |
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Term
| What are three main forms of flow control at layer 4? |
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Definition
congestion avoidance window size buffering |
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Term
| What does collision detection require for half-duplex links? |
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Definition
| A loopback circuit for collision detection. |
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Term
| What does the MTU stand for and what does it determine? |
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Definition
Maximum Transmission Unit Detemines the max size of the packet that can be sent from the specified interface. |
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Term
| What kind of interfaces do/do not show up in the ARP table for a router? |
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Definition
Ethernet interfaces do show up.
Serial interfaces do not show up. |
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Term
| What are the characteristics of a DHCP Discover message? |
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Definition
Sent from client to server
Broadcast on L2 network over UDP port 67 |
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Term
| What are the characteristics of a DHCP Offer message? |
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Definition
Sent from DHCP server to client
Unicast on L2 network over UDP port 68 |
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Term
| How does DHCP check for address conflicts during IP address assignment? |
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Definition
During address assignment, DHCP checks for conflicts using ping and gratuitous ARP.
If a conflict is detected, the address is removed from the pool. The address will not be assigned until the administrator resolves the conflict. |
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Term
| What are the 7 common values that define an IP flow for Netflow? |
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Definition
Unidirectional sequence of packets common values:
- Source IP address
- Destination IP address
- Source port number
- Destination port number
- Layer 3 protocol type
- ToS
- Input logical interface
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Term
| What is a gratuitous ARP and what is it for? |
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Definition
ARP Response that was not prompted by an ARP Request.
It is way for a node to broadcast/update its IP to MAC mapping to the entire network. |
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Term
| What are the characteristics of a half duplex, and full duplex connection. |
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Definition
half duplex: Only one device can use the wire at a time. Connections are considered multipoint.
full duplex: Devices can send and receive at the same time. Connections are considered point-to-point. |
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Term
| What happens to collision detection on a switch port when a device is connected to it at full duplex? |
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Definition
| The collision detection circuit is disabled. |
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Term
What kind of cable connects:
WAN connection from router to router
LAN connect between routers
from host NIC to router
from host NIC to switch
from router to switch
switch to another switch
switch to hub
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Definition
router to router over WAN - serial
NIC/router to router - crossover
NIC/router to switch - straight-through
switch to switch/hub - crossover |
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Term
Describe the pinouts of the following cables:
rollover
straight through
crossover |
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Definition
rollover: pins 1-8 connected to 8-1 respectively
straight through: pins 1-8 connected to 1-8
crossover: pins 1-3 & 2-6 are connected, the rest connected straight through |
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Term
| What situations should Fiber cables be used over UTP? |
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Definition
Longer distances or higher bandwidth than UTP:
- Separate buildings in same campus.
- Switch to switch connections in a building (via transceivers)
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