Data link layer

From Computing and Software Wiki

---

Revision as of 01:12, 23 March 2008

Data link layer

description: The link layer, which is the method used to move packets from the network layer on two different hosts, is not really part of the Internet protocol suite, because IP can run over a variety of different link layers. The processes of transmitting packets on a given link layer and receiving packets from a given link layer can be controlled both in the software device driver for the network card, as well as on firmware or specialist chipsets. These will perform data link functions such as adding a packet header to prepare it for transmission, then actually transmit the frame over a physical medium.

For Internet access over a dial-up modem, IP packets are usually transmitted using PPP. For broadband Internet access such as ADSL or cable modems, PPPoE is often used. On a local wired network, Ethernet is usually used, and on local wireless networks, IEEE 802.11 is usually used. For wide-area networks, either PPP over T-carrier or E-carrier lines, Frame relay, ATM, or packet over SONET/SDH (POS) are often used.

attack: it is the easiest, & can only be done on local network

1. APR poisoning

2.Switch's routing table looks like this:

      mcaddress              ip
   ..blah...blah..        ..192.168....
   ....blah blah..        ....192.168.1..
  

the pirate will fill the routing table with mc IDs saying you are all of them. (is is called spoofing)

defense:

1. read only routing table: preferred method

2.