Introduction
24
Spectrum24 AP-4111 DS Access Point Product Reference Guide
A TIM is a compressed virtual bitmap identifying the AP associated MUs in
PSP mode that have buffered directed messages. MUs issue a poll request
when APs issue a TIM. A beacon with the broadcast-indicator bit set causes
the MU to note
DTIM Count
field value. The value informs the MU of the
beacons remaining before next DTIM. This ensures the MU turns on the
receiver for the DTIM and the following
BC/MC packet transmissions
.
1.3.9 Data
Encryption
Spectrum24 devices operating on a wired or wireless network face possible
information theft. This occurs when an unauthorized user eavesdrops on
someone else to obtain information illegally. The absence of a physical
connection makes wireless links particularly vulnerable to this form of theft.
Encryption
becomes the most efficient method in preventing information theft
and improving data security. Encryption entails scrambling and coding
information, typically with mathematical formulas called
algorithms
, before
the information is transmitted over a network. An algorithm is a set of
instructions or formula for scrambling the data. A
key
is the specific code
used by the algorithm to encrypt or decrypt the data.
Decryption
is the
decoding and unscrambling of received encrypted data. The same device,
host computer or front-end processor, usually performs both encryption and
decryption. The data transmit or receive direction determines whether the
encryption or decryption function is performed. This device takes the plain
text and scrambles or encrypts it and transmitting the data over the network,
typically by mathematically combining the key with the plain text as
prescribed by the algorithm. At the receiving end another device takes the
encrypted text and decrypts, unscrambles, the text resulting in the original
plain text. An authorized user can know the algorithm, but cannot interpret
the encrypted data without the appropriate key. Only the sender and receiver
of the transmitted data know the key.
Symbol uses the
Wired Equivalent Privacy (WEP)
algorithm, specified in IEEE
802.11 section 8, for encryption and decryption. WEP uses the same key
for both encrypting and decrypting plain text. Typically an external key
management service distributes the key. Users should change the key often
for added security. IEEE 802.11 defines two types of
authentication
,
Open
System
and
Shared Key. Open system authentication
is a null authentication
Summary of Contents for AP-4111 DS
Page 112: ...Monitoring Statistics 104 Spectrum24 AP 4111 DS Access Point Product Reference Guide ...
Page 120: ...Hardware Installation 112 Spectrum24 AP 4111 DS Access Point Product Reference Guide ...
Page 124: ...A 4 Spectrum24 Access Point AP 3020 Product Reference Guide ...
Page 126: ...B 2 Spectrum24 Access Point AP 3020 Product Reference Guide ...