Straight-through vs crossover cables

Straight-through vs crossover cables 

(wire 1<-> wire 3, wire 2<-> wire 6):

Considering the devices grouped in two categories: 1-switches / hubs / bridges, 2-workstations / servers / routers

If changing category, use a straight through cable, else use a crossover cable. (or use straight-through when one of the port is marked with an X)

Ethernet Auto-Negotiation:

Ethernet Frames:

Determines the link speed and duplex status.

Ethernet II – uses a two-byte type field instead of the length.

802.3 – cannot identify the upper-layer protocol

802.2 (802.3 with LLC information in the data field of the header) – able to identify the upper layer protocol

SNAP – Subnetwork Access Protocol – used in AppleTalk and Cisco Discovery Protocol)

Half-Duplex:

Contention net using CSMA/CD (Carrier Sense Multiple Access/Collision Detection) and a backoff algorithm when collision occur.

Full-Duplex:

Two communication paths are required and compatible full-duplex NICs. Loopback and collision detection must be disabled. Sets up a point-to-point connection with the remote device. There are no collisions on a Full-Duplex link.

Ring LAN:

                              

Token Ring: standard created by IBM and reflected in IEEE 802.5 with speeds of 4 or 16 Mbps. Stations cannot transmits until they have the token, which they can reserve using the Reservation Bits.

FDDI (Fiber Distributed Data Interface):

                    

Token-passing ANSI standard providing LAN speed of up to 200 Mbps if dual rings are active. Only LAN topology that is both physical and logical ring.

MSAU:

MultiStation Access Unit, the controller of the token ring LAN, for up to 8 stations.

NAUN:

Nearsest Active Upstream Neighbour

Active Monitor:

One station on the ring always ensures there is only ever one token on the ring.

Beaconing:

Process by which a station attempts to determine a network failure.