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IEEE 802 standards
802.1
Internetworking
802.2.
Logical Link Control (LLC)
802.3
Carrier Sense Multiple Access with Collision Detection (CSMA/ CD) LANs
(Ethernet)
802.4
Token Bus LAN
802.5
Token Ring LAN
802.6
Metropolitan Area Network (MAN)
802.7
Broadband Technical Advisory Group
802.8
Fiber Optic Advisory Group
802.9
Integrates Voice and Data Networks
802.10
Network Security
802.11
Wireless Networks
802.12
Demand Priority Access LAN, 100VG-AnyLAN
ISO - International Organization for
Standardization ("isos" - greek word = equal or standard)
P
[dB] = 10 log(P); base = 10;
U[dB]
= 20 log(P); base = 10;
NDIS = Network Driver Interface Specification
A
Windows device driver interface that enables a single network interface card
(NIC) to support multiple network protocols. For example, with NDIS a single
NIC can support both TCP/IP and IPX connections. NDIS can also be used by some
ISDN adapters.
NDIS
includes a protocol manager that accepts requests from the network driver (at
the transport layer) and passes these requests to the NIC (at the data link
layer). So multiple NDIS-conforming network drivers can co-exist. Also, if a
computer contains multiple NICs because it is connected to more than one
network, NDIS can route traffic to the correct card.
NDIS
was developed by Microsoft and 3COM. Novell offers a similar device driver for
NetWare called Open Data-Link Interface (ODI).
ODI = Open Data-link Interface
An
application programming interface (API) developed by Novell for writing network
drivers. ODI separates the physical network layer (the Data-Link Layer in the
OSI model) from the network protocol layer (the Transport Layer). As a result,
the same network interface card (NIC) can be used to carry data for different
protocols. For example, ODI allows a computer with just one NIC to be
simultaneously connected to both an IPX/SPX network and a TCP/IP
An AppleTalk address consists of a network number and a node number expressed
in decimal in
the format network . node.
The following is an example of an AppleTalk
network address: 3.69. In this example, the network
number is 3 and the node number is 69.
The network
number identifies a network, or cable segment. A network is a single
logical cable. Although the logical cable is frequently a single physical
cable, bridges and routers can interconnect several physical cables.
The network number is a 16-bit (or less) decimal
number that must be unique throughout the entire AppleTalk internetwork.
In AppleTalk Phase 1, networks are identified by a
single network number that corresponds to a physical network. In AppleTalk
Phase 1, the network number 0 is reserved.
In AppleTalk Phase 2, networks are identified by a
cable range that corresponds to one or more logical networks. In Phase 2, a
single cable can have multiple network numbers.
A cable range is either one network number or a contiguous sequence of
several network numbers in the format start-end. For example, the
cable range 4096-4096 identifies a logical network that has a single network
number, and the cable range 10-12 identifies a logical network that spans three
network numbers.
In AppleTalk Phase 2, the network number 0 is
reserved.
The node
number identifies the node, which is any
device connected to the AppleTalk network. The node number is an 8-bit decimal number that
must be unique on that network.
In AppleTalk Phase 1, node numbers 1 through 127
are for user nodes, node numbers 128 through 254 are for servers, and node
numbers 0 and 255 are reserved.
In AppleTalk Phase 2, you can use node numbers 1
through 253 for any nodes attached to the network. Node numbers 0, 254, and 255
are reserved.
A zone is a logical group of networks. The networks in a zone can
be contiguous or noncontiguous. A zone is identified by a zone name, which can
be up to 32 characters long. The zone name can include standard characters and
AppleTalk special characters. To include a special character, type a colon
followed by two hexadecimal characters that represent the special character in
the Macintosh character set.
An AppleTalk Phase 1 network can have only one
zone.
In AppleTalk Phase 2, an extended network can have
up to 255 zones; a nonextended network can have only 1 zone.
AppleTalk Phase 1 and AppleTalk Phase 2 networks
are incompatible and cannot run simultaneously on the same internetwork. As a
result, all routers in an internetwork must support AppleTalk Phase 2
before the network can use Phase 2 routing.
If your internetwork has a combination of
AppleTalk Phase 1 and Phase 2 routers, you must observe the following
configuration guidelines. If you do not follow these guidelines, unpredictable
behavior might result. Note, however, that you do not need to upgrade all end
nodes to use the features provided by our AppleTalk enhancements.
·
The cable range must be one
(for example, 23-23).
The Netware
Internetwork Packet Exchange (IPX) Protocol is an implementations of Xerox's
Internetwork Packet Protocol. The purpose of IPX is to allow applications
running on a Netware workstation to take advantage of the Netware network
drives to communicate with other workstations, servers, or devices on the
internetwork.
IPX Internetwork Packets
The packet structure of IPX packets is precisely the structure of Xerox's XNS
packets. The packet structure will be briefly outlined below.
General Structure of IPX Packets
An IPX packet consists of 30 bytes of header followed by 0 to 546 bytes of
data. Thus, the minimum packet length is 30 bytes, and the maximum length is
576 bytes.
Structure of IPX Packet Headers
The IPX header (first 30
bytes of all packets) must conform to the following format:
Offset Field Size Data Type---------------------------------------------------------------- 0 Checksum 2 bytes 1's compl. integer 2 Length 2 bytes high-low unsigned integer 4 Transport Control 1 byte unsigned integer 5 Packet Type 1 byte unsigned integer 6 Destination Network 4 bytes high-low unsigned integer10 Destination Node 6 bytes high-low unsigned integer16 Destination Socket 2 bytes high-low unsigned integer 18 Source Network 4 bytes high-low unsigned integer22 Source Node 6 bytes high-low unsigned integer28 Source Socket 2 bytes high-low unsigned integer----------------------------------------------------------------
Note that
numeric fields composed of more than 1 byte can be in two opposite formats:
high-low(h-l) and low-high. High-low numbers contain the most significant byte
in the first byte of the field, the next-most significant byte in the second
byte, and so on, with the least significant byte appearing last. Low-high
numbers are stored in exactly the opposite order.
Description of Header
Contents
Checksum
This field is a one's complement add and left cycle checksum of the 16-bit
words in the packed header. This field will contain a -zero (FFFFh) if no
checksum is desired. If a calculated checksum comes to -zero then it should be
reset to +zero (0000h).
Note that field is a
checksum of the 30-byte header only. If applications wish to checksum their own
data then they should provide their own checksum in some agreed-upon portion of
data area.
A given NetWare hell
implementation may not verify this checksum when receiving a packed. If header
checksum verification is required, then it should be performed by the
application to whom the packed is delivered.
Length
This field contain the length of the complete network packed, which is the
length of the header plus the length of the data section. Therefore, the
minimum length of a packed is 30-bytes, and the maximum length of a packet is
576 bytes.
Transport Control
This field is used by Netware Internetwork bridges and is always set to zero
before a packed is sent.
Packet Type
This field indicates the "type" of service offered or required by the
packet; Xerox has defined the following values:
0 Unknown packed type1 Routing Information Packet2 Echo packet3 Error packet4 Packet Exchange Packet5 Sequenced Packet Protocol Packet16-31 Experimental Protocol
Users are
strongly encouraged to use either packet type 0 or packet type 4 in all their
packets.
Destination Network
This field contain a network number of the destination network where the node
can be found to whom the packet is addressed.
Under Advanced NetWare,
networks connected on an internetwork are assigned 4-byte networks number by a
network administrator. Each network on a connected internetwork is required to
have a unique number.
If this field is set to 0,
the destination node is assumed to reside on the same physical network to which
the source node is connected; the packet will be sent without involving an
Advanced NetWare Internetwork Bridge.
Destination Node
This field contain a 6-byte number which identifies the physical address (on
the destination network) of the node to which the packet is destined.
Note that not all physical
LAN topologies use same size address fields. A node on an EtherNet network
would require all 6 bytes to specify its address, while a node on an OmniNet
network would require only 1 byte.
If a physical network needs
less than 6 bytes to specify node addresses, then the portion of the address
needed should occupy the least significant (last) portion of this field and the
first bytes of the field should be set to zeroes.
Setting all six bytes to
FFh indicates that the packet should be broadcast to all nodes on the specified
network. Broadcast to all nodes on a network may or may not be supported,
depending on the physical characteristics (i.e. broadcast support) of the
underlying physical network to which the packet is destined.
Destination Socket
This fields contains the socket address of the software routine to which the
packet is destined.
Socket numbers are used to
route packets to different software routines within a given node. Xerox has
reserved certain sockets for special use. Pre-defined sockets are as follows:
1 Routing Information packet2 Echo protocol packet3 Error handler packet32-63 Experimental
Sockets
with numbers below 3.000 (decimal) are considered "well-known"
sockets with statically assigned meanings, while sockets with numbers above
3.000 are dynamically assignable sockets.
Applications developers
that wish to produce a unique well-known socket may request that Xerox assign
them one. A small fee and some amount of processing time may be required by
Xerox. Novell has obtained from Xerox a set of sockets for various uses in the
Advanced NetWare environment. For example, NetWare File Servers accept requests
addressed to socket 0451h.
Because it is unlikely that
NetWare systems will frequently find themselves co-existing with bona fide
Xerox networking software, Novell has decided to offer an alternative scheme
for addressing socket numbers. Novell will administrate a list of sockets that
will be well-known in all NetWare environments. Software developers writing
value-added packages for NetWare should find it simpler to obtain socket assignments
from Novell. Numbers assigned by Novell begin at 8000h (32.768 decimal).
Dynamic socket numbers begin at 4000h.
Source Network
This field contains the network number of the LAN to which the node that
originated the packet is connected. this field may contain a value of zero,
indicating an "unknown" number for the network to which the source
node is physically connected.
Incidentally, all packets
with a zero in this field which pass through an Advanced NetWare Internetwork
Bridge will have this field set with the real source network number. Thus, when
a packet is received from a node on a different network, the Source Network
field will always be set properly; packets originated by a node on the same
network as the receiving node are the only packets which may still contain a
value of zero in this field.
Source Node
This field contain the physical address of the node from which the packet
originated.
How many bytes of this
address are actually used to address the given node is a function of the physical
network to which the node is connected. See the related discussion in the
preceding definition of the Destination Node field.
Source socket
This field contain the socket address being used by the software routine that
originated the packet.
Although it is not required
by the IPX protocol, it is usual for all stations communicating about a
particular task in a peer-to-peer fashion to send and receive using the same
socket number. In a client/server situation, the node which is acting as a server
(perhaps a communicating gateway) would likely be listening on a specific
socket for request to service. In such cases, the source socket is not
necessary the same or even significant; all that matters is that the server
reply to the given source socket.
For example, all Advanced
NetWare file servers have the same socket address, but request to them may be
originated by clients using any socket number.
If
software developers wish to have a uniquely assigned static socket to
communicate on then they should contact Xerox or Novell to have a socket number
assigned to him.