A MAC address is 48 bits long and is represented as a
hexadecimal number. Represented in hex, it is 12 characters in length, where
each character is 4 bits. To make it easier to read, the MAC address is
represented in a dotted hexadecimal format, like this: FFFF.
FFFF.FFFF.
Some formats use a colon (:) instead; and in Some cases, the
colon separator is spaced after every two hexadecimal digits, like this:FF:FF:FF:FF:FF:FF. the first six digits of a MAC address are
associated with the vendor, or maker, of the NIC.
Each vendor has one or more unique sets of six digits. These
first six digits are commonly called the organizationally unique identifier
(OUI). The last six digits
are used to represent the NIC uniquely within the OUI value. In theory, each
NIC has a unique MAC address. In reality however, this is probably not true.
What is important for your purposes is that each of your NICs has a unique MAC
address within the same physical or logical segment.
A logical segment is a virtual LAN (VLAN) and is referred to as
a broadcast domain .
Some devices, such as Cisco routers, might allow you to change
the MAC address for a NIC, while others won't.
Every data link layer frame has two MAC addresses: a source MAC
address of the host creating
the frame and a destination MAC addressfor the device (or devices, in the cast of a
broadcast or multicast) intended to receive the frame.
If only one device is to receive the frame, a unicast
destination MAC address is used. If all devices need to receive the frame, a
destination broadcast address is used.
When all the binary bits are enabled for a MAC address, this is
referred to as a local broadcast address: FFFF.FFFF.FFFF.
OSI (Open Systems
Interconnect) layers and network components operate:
Hubs Switches, Bridges, Routers, NICs (Network Interface Card),
WAPs (Wireless Access Point)
Seven layers of the
OSI (Open Systems Interconnect) model and their functions.
Network protocols in
terms of routing, addressing schemes, interoperability and naming conventions:
TCP/IP
Transmission Control Protocol, A connection based Internet protocol
responsible for breaking data into packets, which the IP protocol sends over
the network. IP is located at the TCP/IP Internet layer which corresponds to
the network layer of the OSI Model. IP is responsible for routing packets by
their IP address.
IP is a connectionless protocol. which means, IP does not establish
a connection between source and destination before transmitting data, thus
packet delivery is not guaranteed by IP. Instead, this must be provided by TCP.
TCP is a connection based protocol and, is designed to guarantee delivery by
monitoring the connection between source and destination before data is transmitted.
TCP places packets in sequential order and requires acknowledgment from the
receiving node that they arrived properly before any new data is sent.
TCP/IP model
|
Application layer
|
|
DHCP - DNS - FTP -
HTTP - IMAP4 - IRC - NNTP - XMPP - MIME - POP3 - SIP - SMTP - SNMP - SSH -
TELNET - BGP - RPC - RTP - RTCP - TLS/SSL - SDP - SOAP - L2TP - PPTP
|
|
Transport layer
|
|
This layer deals
with opening and maintaining connections, ensuring that packets are in fact
received. This is where flow-control and connection protocols exist, such as:
TCP - UDP - DCCP - SCTP - GTP
|
|
Network layer
|
|
IP (IPv4 - IPv6) -
ARP - RARP - ICMP - IGMP - RSVP - IPSec - IPX/SPX
|
|
Data link layer
|
|
ATM - DTM - Ethernet
- FDDI - Frame Relay - GPRS - PPP
|
|
Physical layer
|
|
Ethernet physical
layer - ISDN - Modems - PLC - RS232 - SONET/SDH - G.709 - Wi-Fi
|
IPX/SPX
IPX/SPX is the primary protocol of Novell NetWare (in
particular, versions 4.0 and earlier, though it can be used on all versions).
Internetwork Packet Exchange/Sequenced Packet Exchange developed by Novell and
is used primarily on networks that use the Novell NetWare network operating
system. The IPX and SPX protocols provide services similar to those offered by
IP and TCP. Like IP, IPX is a connectionless network layer protocol. SPX runs on
top of IPX at the transport layer and, like TCP, provides connection oriented,
guaranteed delivery. IPX/SPX provides many of the same features as TCP/IP, and
is a routable transport protocol that allows networks to be segmented. However,
network segmentation with IPX/SPX is done with network numbers and not with
subnet masks. IPX/SPX is also similar to TCP/IP because IPX/SPX relies on
internal protocols for network communication.
IPX
IPX is similar to the operation of UDP of TCP/IP. IPX is a
connectionless datagram transfer service. Because it is connectionless, like
UDP, it does not require any preliminary connection setup to transmit the data
packets. A disadvantage to connectionless communication is that flow control
and error correction are not provided during network communication. In
addition, packet delivery is not guaranteed. IPX also provides addressing and
routing of packets within and between network segments.
SPX
SPX is similar to the operation of TCP of TCP/IP. SPX is
connection-oriented data transfer over IPX. Because SPX is connection oriented,
flow control and error correction are provided along with packet delivery
acknowledgments. SPX allows a single packet to remain unacknowledged at one
time. If a packet is unacknowledged, the packet is retransmitted a total of 8
times. If there’s no acknowledgment, SPX considers the connection failed.
SPXII
SPXII is an enhancement to SPX. SPXII has several improvements
over SPX. SPXII allows more than one packet to remain unacknowledged. SPXII
also allows for a larger packet size, which improves network performance by
reducing the number of acknowledgment packets placed on the network.
NetBEUI
NetBIOS Enhanced User Interface was designed as a small,
efficient protocol for use in department-sized LANs of 20-200 computers that do
not need to be routed to other subnets. NetBEUI is used almost exclusively on
small, non-routed networks. A LAN-only (non-routable) protocol used in early
Windows networks based on the NetBIOS API, NetBEUI is a Windows protocol that
even Microsoft doesn't recommend for any but the most isolated networks.
NetBEUI isn't required for NetBIOS functionality. As an extension of NetBIOS,
NetBEUI is not routable, therefore networks supporting NetBEUI must be
connected with bridges, rather than routers, like NetBIOS, the NetBEUI
interface must be adapted to routable protocols like TCP/IP for communication
over WANs.
AppleTalk
The AppleTalk routing protocol is, amazing as it may sound, used
by Macintosh networks. There are two important factors to understand about the
AppleTalk protocol: zones and network numbers. AppleTalk network numbers assign
AppleTalk networks unique numerical values that identify them as segments.
Clients and servers can be part of only one network number. Because AppleTalk
is routable, clients can access servers from any network number. AppleTalk also
uses zones to aid clients in browsing an AppleTalk network. Zones allow
servers, printers, and clients to be grouped logically for the purpose of
resource access. Unlike network numbers, servers, printers, and clients can be
part of more than one zone. Having membership in more than one zone allows
clients easier access to network resources. Clients need not use the Chooser to
view the resources of multiple zones.
Comments
Post a Comment