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Prepare for an eye-opener when you realize how much a typical app relies on all of these (and many more) working flawlessly... and how you can prepare your app for failure in the chain.
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Note that some slides are borrowed.
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The evolution and principles of networking;
The basic notions used in this domain;
Types of equipment;
Description and general information of basic networking protocols.
The practical examples provide configuration commands, packet captures and a real feel of how to build a simple network
The course attendees will be encouraged to show their understanding by answering questions and debating the issues and solutions that they might have encountered when working with networks.
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Our job might be to build web applications, but we can't build apps that rely on networking if we don't know how these networks and the big network that connects them all (this thing called the Internet) actually work.
I'll walk through the basics of networking, then dive a lot deeper (from TCP/UDP to IPv4/6, source/destination ports, sockets, DNS and even BGP).
Prepare for an eye-opener when you realize how much a typical app relies on all of these (and many more) working flawlessly... and how you can prepare your app for failure in the chain.
WSN protocol 802.15.4 together with cc2420 seminars Salah Amean
WSN protocol 802.15.4 together with cc2420 seminars . It is based on the standand of ieee802.15.4 and data sheet of the radio transceiver cc2420.
Note that some slides are borrowed.
This course describes the basic networking elements and how they are used in practice. The course covers:
The evolution and principles of networking;
The basic notions used in this domain;
Types of equipment;
Description and general information of basic networking protocols.
The practical examples provide configuration commands, packet captures and a real feel of how to build a simple network
The course attendees will be encouraged to show their understanding by answering questions and debating the issues and solutions that they might have encountered when working with networks.
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The alleged breach affected Europol agencies CCSE, EC3, Europol Platform for Experts, Law Enforcement Forum, and SIRIUS. Infiltration of these entities can disrupt ongoing investigations and compromise sensitive intelligence shared among international law enforcement agencies.
However, this is neither the first nor the last activity of IntekBroker. We have compiled for you what happened in the last few days. To track such hacker activities on dark web sources like hacker forums, private Telegram channels, and other hidden platforms where cyber threats often originate, you can check SOCRadar’s Dark Web News.
Stay Informed on Threat Actors’ Activity on the Dark Web with SOCRadar!
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2. MAC addresses
Link Layer: 6-2
32-bit IP address:
• network-layer address for interface
• used for layer 3 (network layer) forwarding
• e.g.: 128.119.40.136
MAC (or LAN or physical or Ethernet) address:
• function: used “locally” to get frame from one interface to another
physically-connected interface (same subnet, in IP-addressing sense)
• 48-bit MAC address (for most LANs) burned in NIC ROM, also
sometimes software settable
hexadecimal (base 16) notation
(each “numeral” represents 4 bits)
• e.g.: 1A-2F-BB-76-09-AD
3. MAC addresses
Link Layer: 6-3
each interface on LAN
has unique 48-bit MAC address
has a locally unique 32-bit IP address (as we’ve seen)
1A-2F-BB-76-09-AD
58-23-D7-FA-20-B0
0C-C4-11-6F-E3-98
71-65-F7-2B-08-53
LAN
(wired or wireless)
137.196.7/24
137.196.7.78
137.196.7.14
137.196.7.88
137.196.7.23
4. MAC addresses
Link Layer: 6-4
MAC address allocation administered by IEEE
manufacturer buys portion of MAC address space (to
assure uniqueness)
analogy:
• MAC address: like Social Security Number
• IP address: like postal address
MAC flat address: portability
• can move interface from one LAN to another
• recall IP address not portable: depends on IP subnet to which
node is attached
5. ARP: address resolution protocol
Link Layer: 6-5
ARP table: each IP node (host,
router) on LAN has table
Question: how to determine interface’s MAC address, knowing its IP
address?
1A-2F-BB-76-09-AD
58-23-D7-FA-20-B0
0C-C4-11-6F-E3-98
71-65-F7-2B-08-53
LAN
137.196.7.78
137.196.7.14
137.196.7.88
137.196.7.23
ARP
ARP
ARP
ARP
• IP/MAC address mappings for
some LAN nodes:
< IP address; MAC address; TTL>
• TTL (Time To Live): time after
which address mapping will be
forgotten (typically 20 min)
6. ARP protocol in action
Link Layer: 6-6
58-23-D7-FA-20-B0
137.196.7.14
B
C
D
TTL
71-65-F7-2B-08-53
137.196.7.23
A
ARP table in A
IP addr MAC addr TTL
example: A wants to send datagram to B
• B’s MAC address not in A’s ARP table, so A uses ARP to find B’s MAC address
A broadcasts ARP query, containing B's IP addr
• destination MAC address = FF-FF-FF-FF-FF-FF
• all nodes on LAN receive ARP query
1
Source MAC: 71-65-F7-2B-08-53
Source IP: 137.196.7.23
Target IP address: 137.196.7.14
…
1
Ethernet frame (sent to FF-FF-FF-FF-FF-FF)
7. ARP protocol in action
Link Layer: 6-7
58-23-D7-FA-20-B0
137.196.7.14
B
C
D
TTL
71-65-F7-2B-08-53
137.196.7.23
A
ARP table in A
IP addr MAC addr TTL
example: A wants to send datagram to B
• B’s MAC address not in A’s ARP table, so A uses ARP to find B’s MAC address
B replies to A with ARP response,
giving its MAC address
2
Target IP address: 137.196.7.14
Target MAC address:
58-23-D7-FA-20-B0
…
2
ARP message into Ethernet frame
(sent to 71-65-F7-2B-08-53)
8. ARP protocol in action
Link Layer: 6-8
58-23-D7-FA-20-B0
137.196.7.14
B
C
D
TTL
71-65-F7-2B-08-53
137.196.7.23
A
ARP table in A
IP addr MAC addr TTL
example: A wants to send datagram to B
• B’s MAC address not in A’s ARP table, so A uses ARP to find B’s MAC address
A receives B’s reply, adds B entry
into its local ARP table
3
137.196.
7.14
58-23-D7-FA-20-B0 500
9. Routing to another subnet: addressing
Link Layer: 6-9
walkthrough: sending a datagram from A to B via R
focus on addressing – at IP (datagram) and MAC layer (frame) levels
R
A B
1A-23-F9-CD-06-9B
222.222.222.220
111.111.111.110
E6-E9-00-17-BB-4B
CC-49-DE-D0-AB-7D
111.111.111.112
111.111.111.111
74-29-9C-E8-FF-55 222.222.222.222
49-BD-D2-C7-56-2A
222.222.222.221
88-B2-2F-54-1A-0F
assume that:
• A knows B’s IP address
• A knows IP address of first hop router, R (how?)
• A knows R’s MAC address (how?)
10. Routing to another subnet: addressing
Link Layer: 6-10
R
1A-23-F9-CD-06-9B
222.222.222.220
111.111.111.110
E6-E9-00-17-BB-4B
CC-49-DE-D0-AB-7D
111.111.111.112
111.111.111.111
74-29-9C-E8-FF-55
A
222.222.222.222
49-BD-D2-C7-56-2A
222.222.222.221
88-B2-2F-54-1A-0F
B
IP
Eth
Phy
IP src: 111.111.111.111
IP dest: 222.222.222.222
A creates IP datagram with IP source A, destination B
A creates link-layer frame containing A-to-B IP datagram
• R's MAC address is frame’s destination
MAC src: 74-29-9C-E8-FF-55
MAC dest: E6-E9-00-17-BB-4B
11. Routing to another subnet: addressing
Link Layer: 6-11
R
1A-23-F9-CD-06-9B
222.222.222.220
111.111.111.110
E6-E9-00-17-BB-4B
CC-49-DE-D0-AB-7D
111.111.111.112
111.111.111.111
74-29-9C-E8-FF-55
A
222.222.222.222
49-BD-D2-C7-56-2A
222.222.222.221
88-B2-2F-54-1A-0F
B
IP
Eth
Phy
frame sent from A to R
IP
Eth
Phy
frame received at R, datagram removed, passed up to IP
MAC src: 74-29-9C-E8-FF-55
MAC dest: E6-E9-00-17-BB-4B
IP src: 111.111.111.111
IP dest: 222.222.222.222
IP src: 111.111.111.111
IP dest: 222.222.222.222
12. Routing to another subnet: addressing
Link Layer: 6-12
R
1A-23-F9-CD-06-9B
222.222.222.220
111.111.111.110
E6-E9-00-17-BB-4B
CC-49-DE-D0-AB-7D
111.111.111.112
111.111.111.111
74-29-9C-E8-FF-55
A
222.222.222.222
49-BD-D2-C7-56-2A
222.222.222.221
88-B2-2F-54-1A-0F
B
IP src: 111.111.111.111
IP dest: 222.222.222.222
MAC src: 1A-23-F9-CD-06-9B
MAC dest: 49-BD-D2-C7-56-2A
R determines outgoing interface, passes datagram with IP source A, destination B
to link layer
R creates link-layer frame containing A-to-B IP datagram. Frame destination
address: B's MAC address
IP
Eth
Phy
13. Routing to another subnet: addressing
Link Layer: 6-13
R
1A-23-F9-CD-06-9B
222.222.222.220
111.111.111.110
E6-E9-00-17-BB-4B
CC-49-DE-D0-AB-7D
111.111.111.112
111.111.111.111
74-29-9C-E8-FF-55
A
222.222.222.222
49-BD-D2-C7-56-2A
222.222.222.221
88-B2-2F-54-1A-0F
B
IP
Eth
Phy
IP
Eth
Phy
IP src: 111.111.111.111
IP dest: 222.222.222.222
MAC src: 1A-23-F9-CD-06-9B
MAC dest: 49-BD-D2-C7-56-2A
transmits link-layer frame
R determines outgoing interface, passes datagram with IP source A, destination B
to link layer
R creates link-layer frame containing A-to-B IP datagram. Frame destination
address: B's MAC address
14. Routing to another subnet: addressing
Link Layer: 6-14
R
1A-23-F9-CD-06-9B
222.222.222.220
111.111.111.110
E6-E9-00-17-BB-4B
CC-49-DE-D0-AB-7D
111.111.111.112
111.111.111.111
74-29-9C-E8-FF-55
A
222.222.222.222
49-BD-D2-C7-56-2A
222.222.222.221
88-B2-2F-54-1A-0F
B
IP
Eth
Phy
IP
Eth
Phy
B receives frame, extracts IP datagram destination B
B passes datagram up protocol stack to IP
IP src: 111.111.111.111
IP dest: 222.222.222.222
16. Ethernet
Link Layer: 6-16
“dominant” wired LAN technology:
first widely used LAN technology
simpler, cheap
kept up with speed race: 10 Mbps – 400 Gbps
single chip, multiple speeds (e.g., Broadcom BCM5761)
Metcalfe’s Ethernet
sketch
https://www.uspto.gov/learning-and-resources/journeys-innovation/audio-stories/defying-doubters
17. Ethernet: physical topology
Link Layer: 6-17
bus: popular through mid 90s
• all nodes in same collision domain (can collide with each other)
bus: coaxial cable switched
switched: prevails today
• active link-layer 2 switch in center
• each “spoke” runs a (separate) Ethernet protocol (nodes do not collide with
each other)
18. Ethernet frame structure
Link Layer: 6-18
sending interface encapsulates IP datagram (or other network layer
protocol packet) in Ethernet frame
dest.
address
source
address data (payload) CRC
preamble
type
preamble:
used to synchronize receiver, sender clock rates
7 bytes of 10101010 followed by one byte of 10101011
19. Ethernet frame structure (more)
Link Layer: 6-19
dest.
address
source
address data (payload) CRC
preamble
type
addresses: 6 byte source, destination MAC addresses
• if adapter receives frame with matching destination address, or with broadcast
address (e.g., ARP packet), it passes data in frame to network layer protocol
• otherwise, adapter discards frame
type: indicates higher layer protocol
• mostly IP but others possible, e.g., Novell IPX, AppleTalk
• used to demultiplex up at receiver
CRC: cyclic redundancy check at receiver
• error detected: frame is dropped
20. Ethernet: unreliable, connectionless
Link Layer: 6-20
connectionless: no handshaking between sending and
receiving NICs
unreliable: receiving NIC doesn’t send ACKs or NAKs to
sending NIC
• data in dropped frames recovered only if initial sender uses
higher layer rdt (e.g., TCP), otherwise dropped data lost
Ethernet’s MAC protocol: unslotted CSMA/CD with binary
backoff
21. 802.3 Ethernet standards: link & physical layers
Link Layer: 6-21
• different physical layer media: fiber, cable
application
transport
network
link
physical
MAC protocol
and frame format
100BASE-TX
100BASE-T4
100BASE-FX
100BASE-T2
100BASE-SX 100BASE-BX
fiber physical layer
copper (twister pair) physical layer
many different Ethernet standards
• common MAC protocol and frame format
• different speeds: 2 Mbps, 10 Mbps, 100 Mbps, 1Gbps, 10 Gbps, 40 Gbps
23. Ethernet switch
Link Layer: 6-23
Switch is a link-layer device: takes an active role
• store, forward Ethernet frames
• examine incoming frame’s MAC address, selectively forward frame
to one-or-more outgoing links when frame is to be forwarded on
segment, uses CSMA/CD to access segment
transparent: hosts unaware of presence of switches
plug-and-play, self-learning
• switches do not need to be configured
24. Switch: multiple simultaneous transmissions
Link Layer: 6-24
switch with six
interfaces (1,2,3,4,5,6)
A
A’
B
B’ C
C’
1 2
3
4
5
6
hosts have dedicated, direct
connection to switch
switches buffer packets
Ethernet protocol used on each
incoming link, so:
• no collisions; full duplex
• each link is its own collision
domain
switching: A-to-A’ and B-to-B’ can transmit
simultaneously, without collisions
25. Switch: multiple simultaneous transmissions
Link Layer: 6-25
switch with six
interfaces (1,2,3,4,5,6)
A
A’
B
B’ C
C’
1 2
3
4
5
6
hosts have dedicated, direct
connection to switch
switches buffer packets
Ethernet protocol used on each
incoming link, so:
• no collisions; full duplex
• each link is its own collision
domain
switching: A-to-A’ and B-to-B’ can transmit
simultaneously, without collisions
• but A-to-A’ and C to A’ can not happen
simultaneously
26. Switch forwarding table
Link Layer: 6-26
A
A’
B
B’ C
C’
1 2
3
4
5
6
Q: how does switch know A’ reachable via
interface 4, B’ reachable via interface 5?
A: each switch has a switch table, each
entry:
(MAC address of host, interface to reach
host, time stamp)
looks like a routing table!
Q: how are entries created, maintained
in switch table?
something like a routing protocol?
27. Switch: self-learning
Link Layer: 6-27
A
A’
B
B’ C
C’
1 2
3
4
5
6
switch learns which hosts
can be reached through
which interfaces
A A’
Source: A
Dest: A’
MAC addr interface TTL
Switch table
(initially empty)
A 1 60
• when frame received, switch
“learns” location of sender:
incoming LAN segment
• records sender/location pair
in switch table
28. Switch: frame filtering/forwarding
Link Layer: 6-28
when frame received at switch:
1. record incoming link, MAC address of sending host
2. index switch table using MAC destination address
3. if entry found for destination
then {
if destination on segment from which frame arrived
then drop frame
else forward frame on interface indicated by entry
}
else flood /* forward on all interfaces except arriving interface */
29. A
A’
B
B’ C
C’
1 2
3
4
5
6
Self-learning, forwarding: example
Link Layer: 6-29
A A’
Source: A
Dest: A’
MAC addr interface TTL
switch table
(initially empty)
A 1 60
A A’
A A’
A A’
A A’
A A’
A’ A
A’ 4 60
frame destination, A’,
location unknown: flood
destination A location
known: selectively send
on just one link
30. Interconnecting switches
Link Layer: 6-30
self-learning switches can be connected together:
Q: sending from A to G - how does S1 know to forward frame destined to
G via S4 and S3?
A: self learning! (works exactly the same as in single-switch case!)
A
B
S1
C D
E
F
S2
S4
S3
H
I
G
31. Self-learning multi-switch example
Link Layer: 6-31
Suppose C sends frame to I, I responds to C
Q: show switch tables and packet forwarding in S1, S2, S3, S4
A
B
S1
C D
E
F
S2
S4
S3
H
I
G
33. Switches vs. routers
Link Layer: 6-33
application
transport
network
link
physical
network
link
physical
link
physical
switch
datagram
application
transport
network
link
physical
frame
frame
frame
datagram
6-33
both are store-and-forward:
routers: network-layer devices (examine
network-layer headers)
switches: link-layer devices (examine
link-layer headers)
both have forwarding tables:
routers: compute tables using routing
algorithms, IP addresses
switches: learn forwarding table using
flooding, learning, MAC addresses