Layer 2 - Data Link Layer - Transmission Technologies
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19 terms
Terms | Definitions |
|---|---|
 Main task of the data link layer | transform raw transmission facility into a line that appears free of undetected errors to the network layer. Accomplishes this by having the sender break up the input into frames, and transmit them sequentially. If the service is reliable, the receiver confirms the correct receipt of each frame. |
| Unicast | - associated with point-to-point networks. - point to point transmission with one sender and one receiver. |
| Multicast | transmission of frames to a subset of the machines on the broadcast network. |
| Broadcast | transmission of frames to all machines on the broadcast network. |
| Circuit switching | - needs to establish an end to end path before transmission. - analogue networks. - ISDN - PPP |
| Packet-switching | - chatty. - no dedicated path required. |
| switches | - Similar to bridge in that it routes frames. - most commonly used to connect individual computers. |
| bridges | connects two or more LANs. When a frame arrives, software in the bridge extracts the frame header and looks it up in a table to see where to send the frame. - different line cards for different technologies, Ethernet, FDDI etc. - each line has its own collision domain. |
| WEP | data link layer protocol described by the 802.11 standard. - uses RC4 often reuses IV. - many installations use the same shared key for all users, so each user can read each others traffic. - vulnerable to a number of known attacks. |
| WPA2 | - based on EAP framework; negotiate authentication method at startup. - 802.1X standard. - uses AES |
| SSID | - straight out of the box, no security configured at all. - WAPs are usually configured to broadcast their presence. - each wireless network node and access point needs the same SSID. - could choose not to broadcast SSID. - Also could implement MAC filtering. |
| 802.11b | - developed before 802.11a. - data throughput of up to 11Mbps. - most widely used standard; as a result the frequency is crowded; might run into interference from other wireless devices. - networks secured through use of WPA and WEP. - 2.4 ghz |
| 802.11a | - operates in different frequency range - 5 GHZ. - less prone to interference. - greater speeds. - not as widely used. |
| 802.11g | - backwards compatible with 802.11b so same WAP can service 802.11g and 802.11b. |
| Blue tooth | - available in a range of mobile devices. - operates in both ad-hoc mode and infrastructure mode. - by default security is disabled but does have three security modes, ranging from full data encryption to integrity control. - only authenticates devices, not users. - vulnerable to buffer over flow. |
| Blue jacking (bluetooth) | allows an anonymous message to be displayed on victims device. |
| Blue bug attack (bluetooth) | Attacker can use AT commands on victims cell to initiate calls, send messages etc. |
| ARP | data link layer does not understand IP addresses. ARP sends out request, who owns IP address? this is used to build table of MAC 48 bit addresses to IP addresses. - defined in RFC 826. - vulnerable to ARP poisening ( adding bogus entries to ARP cache). |
| Point to point protocol (PPP) | - used for router-to-router traffic, and home user to ISP traffic. - handle error detection. - allows IP addresses to be negotiated. - so used in dial up it will set-up the connection with ISP and negotiate an IP address. - replaced SLIP in many uses. |
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