link layer Flashcards
(22 cards)
has responsibility of
transferring datagram from one node
to physically adjacent node over a link
data-link layer
addresses used in frame headers to identify
source, destination
MAC
Where is the link layer implemented?
in each and every host
link layer implemented in
“adaptor” (aka network interface
card NIC) or on a chip
Types of errors
1-Single-bit error: only 1 bit in the data unit has changed.
2-Burst error: 2 or more bits in the data unit have changed.
Detection
methods
-Parity check
-Checksum
-Cyclic redundancy
check (CRC)
Uses Module-2 Binary division
Cyclic redundancy check
more powerful error-detection coding
Cyclic redundancy check
Dedicated link between two devices.
point-to-point
More than two
devices share a single link.
broadcast (shared wire or medium)
examples of random access MAC protocols:
slotted ALOHA
ALOHA
CSMA, CSMA/CD
first widely used LAN technology
ethernet
used to synchronize receiver, sender clock rates
preamble
carries frames between VLANS defined over
multiple physical switches
trunk port:
network-layer
devices
routers
link-layer devices
switches
routers: compute tables using
routing algorithms, IP
addresses
switches: compute tables using
learn forwarding
table using flooding, learning,
MAC addresses
frame destination, A’,
location unknown:
flood
destination A location
known:
A’ 4 60
selectively send
on just one link
MAC address allocation administered by
IEEE
used ‘locally” to get frame from one interface to
another physically-connected interface
MAC (or LAN or physical or Ethernet) address:
