Networking TIC

Appendix D - Glossary of Terms

10BaseT

IEEE standard for base band Ethernet.

Node

Location on a network.

AppleTalk

Telecommunications protocol commonly used for interfacing between Macs.

Node number

Final part of address, relating to the specific node.

Bandwidth

A range of frequencies between two defined limits expressed in cycles per second or Hertz (Hz). Also (here), the information carrying capacity of a circuit.

NT1

See Network Termination 1.

Bit error rate (BER)

The ratio of received bits that are in error, usually expressed as a number referenced to a power of 10 (1 error in 10 5 or a BER of 10-5).

PBX

Private Branch Exchange. A private telecommunications exchange that usually includes access to the public switched network.

Bridge

A bridge is a device that moves some kind of network traffic between two or more segments. It does this by looking at a physical destination address (layer two address) in the traffic off of the first segment, and copying the traffic to whichever segment gets the traffic closer to the segment that the address in the traffic indicates is the destination. Bridges are supposed to comply with IEEE 802.1d (the IEEE standard that defined how bridges should work).

PCM

Pulse Code Modulation. A procedure for adapting an analog signal (i.e. voice) into a digital stream for transmission.

Cable range

Each AppleTalk Subnetwork cable is defined by a range start and end. The cable range is defined by network numbers.

RJ-45

Registered Jack type. This is the jack that is commonly used to connect Twisted Pair LANs and for ISDN line connections among other uses.

Ethernet

A popular local area network design (trademarked by Xerox), characterized by 10 Mbps baseband and employing CSMA/CD as the access control mechanism (standardized by IEEE as 802.3).

ROM

Read-only memory.

IP

Internet Protocol. Internet Protocol. Network layer protocol in the TCP/IP stack offering a connectionless internetwork service. IP provides features for addressing, type-of-service specification, fragmentation and reassembly, and security.

Router

A Router is a device that moves some kind of network traffic between two or more Sub Networks. It does this by looking at a destination address in some protocol such as AppleTalk or IP (a layer three address) in the traffic off of the first network, and copying the traffic to whichever network gets the traffic closer to the network that the address in the traffic indicates is the destination. Depending on the type of Router, the address could be one of many different protocols, such as AppleTalk, IP, or DECnet.

ISDN

ISDN stands for Integrated Services Digital Network. This is a digital dial-up telecommunications network that allows data and voice transfer at high speed with high reliability.

Seed Router

A seed router does not automatically learn addresses from the network. In an AppleTalk network there must be at least one seed router which must be turned on first so that other routers in the network can learn addresses from it.

LAN

Local Area Net. A user owned and user operated high-volume data transmission facility connecting a number of communication devices (computers, terminals, printers, etc.) within a single room, building or campus.

Socket

A socket is a logical entity in a node connected to an AppleTalk network. A socket is owned by software that can send and receive data through the socket. There can be 254 different sockets on a node, and various sockets are reserved for different things.

MB

Megabyte = 1,048,576 bytes.

Switch

A switch can be considered as being a high speed multi-port bridge. Some switches fully comply to the 802,1d standard, others implement a proprietary mechanism in order to improve performance. (The LP2500, LS2200 and LP6000 in there default configuration are in compliance with the 802.1d standard - When a Switch is being use in SciNet environment it should in compliance with the 802.1d standard otherwise it can cause "no communication" problems).

Network

A series of points connected by communications channels.

TCP

Transmission Control Protocol normally associated with IP/ Internet Protocol, an internetworking software set originate on the DOD’s Arpanet network; IP equates to OSI Layer 3, TCP to OSI Layer 4 and 5..

Network Numbers

Each AppleTalk sub-network requires a unique cable range or Network Number. The Network Number ensures that traffic from one sub-network can be distinguished from traffic on another sub-network when the two are connected via a Router. In particular, if a network wishes to be on a campus-wide AppleTalk, the numbers must be unique across the campus.

A sub-network can theoretically support up to 255 multiple zones. Two examples of extended networks, and how their numbering works are:

LocalTalk
LocalTalk sub-networks have a single network number, which can theoretically support up to 254 nodes. In reality, 254 is way too many nodes for a LocalTalk network.

EtherTalk Phase 2
Phase 2 uses a range of network numbers, each of which can support up to 253 nodes. EtherTalk Phase 2 is commonly just called EtherTalk.

UniverCD

Interactive, on-line library of product information from Cisco systems available as CD ROM.

Network Termination 1

In ISDN, a network termination functional entity which may include Layer 1 functions such as line termination, maintenance and performance monitoring, timing, powering, and Layer 1 multiplexing.

WAN

Wide Area Network. Data communications network that serves users across a broad geographic area and often uses transmission devices provided by common carriers. Frame Relay, SMDS, and X.25 are examples of WANs. Compare with LAN (local area network) and MAN (Metropolitan Area Network).

Node (AppleTalk)

A number between 1 and 253. The node for each device on a physical network is unique. This number is determined by the device at its boot time, and it keeps that number (at least) until it is powered off or restarted. Node numbers 1-127 are "client" numbers (i.e.: regular Macintoshes), and numbers 128 - 253 are "server" numbers (i.e.: printers and AppleShare file servers).

Zone (AppleTalk)

A zone is basically a text name that represents some or all parts of a network. Zones make it easy to find groups of devices in the Chooser. A zone can consist of only one Sub Network, or it can group together several network numbers into a single "logical" network. This allows devices on EtherTalk and LocalTalk Sub Networks to be seen together in the Chooser under one zone name. Thus allowing all departmental servers and printers to be found in one place, even if they have more than one Sub Network. It is also possible to have a list of zone names that are all used by a single extended network. Any zones in that list could also be used on other Sub Networks. Here are some examples of the use of zone names on networks:

Any machine on the Sub Network 4608-4608 could choose between zones Ripro1 and SCITEX, while a machine on 4611 would have to be in SCITEX. A machine on 8448-8449 or 8450 would have to be in Ripro1, while a machine on 51456-51456 could choose from Ripro1 or OutPut. Any machine on 51458 would have to be in OutPut. So while only three zones would show up in the chooser, there would actually be 6 networks that were connected and accessible.