Alcatel-Lucent OXE Voice over IP.pdf

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Alcatel-Lucent OmniPCX EnterpriseCommunication Server

Voice over IP



Legal notice:

Alcatel, Lucent, Alcatel-Lucent and the Alcatel-Lucent logo are trademarks ofAlcatel-Lucent. All other trademarks are the property of their respectiveowners.

The information presented is subject to change without notice.

Alcatel-Lucent assumes no responsibility for inaccuracies contained herein.

Copyright © 2007 Alcatel-Lucent. All rights reserved.

The CE mark indicates that this product conforms to the following CouncilDirectives:- 89/336/CEE (concerning electro-magnetic compatibility)- 73/23/CEE (concerning electrical safety)- 1999/5/CE (R&TTE)



Chapter 1Overview

Overview .................................................................................................... 1.1

Chapter 2Detailed description

VoIP Overview ......................................................................................... 2.1

IP Network and the Alcatel-Lucent OmniPCX Enterprise CS . 2.1

Voice Processing on IP ........................................................................ 2.2

Coding with/without Compression. ........................................................... 2.3

Coding with/without Silence Suppression ................................................ 2.3

Framing (Packet Assembly) ....................................................................... 2.3

Echo Cancellation ....................................................................................... 2.4

Transfer of Voice Flows .............................................................................. 2.5

Modem/Fax/Data Calls .......................................................................... 2.6

Quality of Service ................................................................................... 2.6

Connection of the Com Server with the Media Gateways ....... 2.6

The H.323 Gateway Function of the Alcatel-Lucent OmniPCXEnterprise CS ........................................................................................... 2.7

Alcatel-Lucent IP-Phones .................................................................... 2.8

Configuring IP Devices ........................................................................ 2.9

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Summary Table ......................................................................................2.10

Chapter 3Call restriction configuration

Document Purpose ................................................................................ 3.1

Call Admission Control on the Same Node. ................................. 3.1

Restriction by Configuring IP Boards ............................................. 3.1

Restricting Calls by VPN Overflow .................................................. 3.2

Chapter 4Glossary

A ................................................................................................................... 4.1

B ................................................................................................................... 4.2

C ................................................................................................................... 4.3

D ................................................................................................................... 4.4

E .................................................................................................................... 4.5

F .................................................................................................................... 4.6

G ................................................................................................................... 4.6

H ................................................................................................................... 4.7

I ..................................................................................................................... 4.8

J ...................................................................................................................4.10

K ..................................................................................................................4.10

L ...................................................................................................................4.10

M ..................................................................................................................4.11

N ..................................................................................................................4.12

O ..................................................................................................................4.12

P ...................................................................................................................4.12

Q ..................................................................................................................4.14

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R ..................................................................................................................4.14

S ...................................................................................................................4.15

T ...................................................................................................................4.16 U ..................................................................................................................4.17

V ...................................................................................................................4.17

W .................................................................................................................4.18

X ...................................................................................................................4.18

Y ...................................................................................................................4.18

Z ...................................................................................................................4.18

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1.1 Overview

The architecture of the Alcatel-Lucent OmniPCX Enterprise Communication Server has beendesigned to use the IP network to support voice and signaling.

The advantages of using the IP network are:

- The same support can be used for both the computer and telephone networks, thusproviding reduced costs and a simplified installation process.

- A standard protocol is used, thus allowing standard terminals to be connected (notably,H323 and SIP terminals).

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Chapter 1

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2.1 VoIP Overview

On an ISDN network, voice is digitized and transported on a channel (or Time Slot) in the formof a continuous flow of bits. The channel is reserved when the call is set up. Transfer rate isguaranteed.

On an IP network, voice is digitized and possibly compressed, and then transformed intodatagrams by the encoder/decoder. These datagrams are then transmitted over the IPnetwork. At reception, voice is extracted from the messages and the digital flow reconstitutedbefore being sent to the recipient.

Figure 2.1: Transmission over ISDN and IP Networks

The part of an IP network that is "inside" a company is often supported by an Ethernetnetwork. Ethernet is a competitive type network and voice frames compete with the frames ofother applications (file transfer, etc.).

The Ethernet network guarantees neither data transfer time (delay) nor data integrity. This isalso the case for the entire IP network, where losses and delay depend on saturation and thecommunication supports used.

Ethernet network throughput (rate) may vary (10 Mb/s, 100 Mb/s, 1 Gb/s).

2.2 IP Network and the Alcatel-Lucent OmniPCX Enterprise CSWith the Alcatel-Lucent OmniPCX Enterprise CS, the IP network is used:

- To connect the Com Server to the Media Gateways.

- To interconnect the Media Gateways.

- To establish a link with VoIP devices: Alcatel-Lucent IP-Phones, Alcatel PCMM, H.323terminals and gateways, SIP terminals.

- Set up an ABC link over IP between two Alcatel-Lucent OmniPCX Enterprise CSs.

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Figure 2.2: Example of IP Network Use

There are two main standards used to manage VoIP calls, both are supported by theAlcatel-Lucent OmniPCX Enterprise CS:

- H.323: used for ABC links over IP and for calls with H.323 terminals and gateways.

- SIP (Session Initiation Protocol): used for calls with SIP phones or gateways.

The H.323 and SIP standards differ with respect to signaling exchanges. For voice transport,both use RTP (Real Time Protocol) and voice is coded using the G711, G723.1 or G729algorithms (see below).

2.3 Voice Processing on IP

Several processing operations are performed on voice calls:

- Coding:

• With or without compression.

• With or without silence suppression.

- Packet assembly.

- Echo cancellation.

The manner in which these processing operations are performed may affect:

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- The bandwidth used by a call.

- Voice quality.

Various configuration operations must be performed to achieve the desired compromise: seethe module Direct RTP in network - Coding configuration.

2.3.1 Coding with/without Compression.

Coding is ensured by "Codecs", also referred to as "Audio codecs", supported by GD, GA andINT-IP boards and by IP-Phones and PCMM equipment. These circuits are programmable.The administrator configures the processing standard to be applied. Standards availableinclude:

- G711, no compression, call rate is then 56 or 64 kbit/s, according to the case. They accept

the "A" or "µ" law. G711 is recommended when there is no bandwidth problem, on a LANfor example.

- G723.1 and G723.1 Appendix A (with silence suppression), call rate is then 6.3 kbit/s.Audio quality is slightly lower than that of the public phone network.

- G729 Annex A and G729 Annex A & Annex B (with silence suppression), call rate is then 8kbit/s. Audio quality is similar to that of the phone network.

A default type of compression (G723.1 or G729A) is managed by the PCX. If the defaultcompressor is not appropriate for a specific access or set, G711 type processing (withoutcompression) may be locally imposed for this access.

2.3.2 Coding with/without Silence Suppression

To reduce voice rate (also referred to as "bandwidth") yet further, the Codecs have a voiceactivity detector that allows no data to be transmitted during pauses (silences) in aconversation. This process would result in total silence at the receiving end. This would beunpleasant for the listener. To avoid this problem, they incorporate a "background noisegenerator" that gives the user the impression that he is using a standard phone line. This"noise" is also referred to as "comfort noise".

On average, silence suppression enables a coefficient of 2 to be gained in transmitted bit rate.

2.3.3 Framing (Packet Assembly)

Before being sent over the IP network, multimedia (voice) data is assembled in packets.Framing is the packet assembly frequency interval. For example, a framing value of 30 msmeans that a voice packet is sent every 30 ms.

2.3.3.1 Framing and Bandwidth

The bandwidth used depends on packet transmission frequency. The relative "weight" ofprotocol (IP/UDP/RTP) headers increases as framing interval decreases: for an example, seetable: Example for G729 .

table 2.1: Example for G729

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Framing (ms) Voice data

(bytes)

IP/UDP/RTP

header(bytes)

IP datagram

(bytes)

Relative

headerweight (%)

Rate (kb/s)

20 20 40 60 66 24

40 40 40 80 50 16

One solution for reducing the bandwidth required for VoIP is to reduce packet transmissionfrequency, i.e. increase the framing interval.

The Alcatel-Lucent OmniPCX Enterprise CS allows IP board (INT-IP, GD, GA board) framinginterval to be configured. Possible values are given in table: Framing Configuration .

table 2.2: Framing Configuration

Algorithm Voice rate (kb/s) Framing (ms) Voice data (bytes) IP rate (kb/s)

G711 64 20 160 80

30 240 75

G729 8 20 20 24

30 30 19

40 (from R6.0) 40 16

G723.1 6.3 30 24 17

2.3.3.2 Impact on Voice Quality

Increasing IP transmission framing interval has two consequences:

- End-to-end transit time is increased.- Voice quality drops off more quickly if a packet is lost: packet loss results in a larger

quantity of data being lost.

These two effects are felt more sharply the more framing interval is increased. The maximumacceptable value is determined by making objective and subjective measurements of voicequality.

2.3.3.3 Negotiation Mechanism

For a call between an IP board and an H.323 device, framing value is negotiated. Each devicecommunicates its framing value. For the IP board, this value is configured in Alcatel-LucentOmniPCX Enterprise CS system options (see the module Direct RTP in network - Codingconfiguration § VoIP Framing). The lowest of the two values is used.

This mechanism may result in a lower framing transmission value being used than thatconfigured on the Alcatel-Lucent OmniPCX Enterprise CS.

For a call between an IP board and an IP-Phone, the framing value configured in systemoptions is used.

2.3.4 Echo Cancellation

For VoIP calls, the various voice processing operations (compression/decompression, packetassembly) and network transit time result in a delay that may cause a troublesome echo.

Compression boards and IP-Phones have their own specific echo cancellation feature.

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For GIP6, GIP6A, MCV8, and MCV24 boards, the maximum echo cancellation value is 32ms.

For GIP4-4, GIP4-1, MADA1, and MADA3 boards, maximum echo cancellation value is128 ms as of R7.0 (64 ms in R6.2 and lower).

2.3.5 Transfer of Voice Flows

Voice flows are transferred on the IP network, except when devices are connected to the sameMedia Gateway.

On Common hardware, the interface with the IP network is ensured by the GA or GD boards.

On Crystal hardware, the interface with the IP network is ensured by the INT-IP A or INT-IP Bboards.

The compressors are provided by daughterboards installed on these boards, as shown in

table: Compressors on IP boards .table 2.3: Compressors on IP boards

Hardware IP boards Daughterboards

Common hardware GD

GA

- MADA1 (from R6.0): 8 comp. max.- MADA3 (from R6.0): 24 comp. max.- MCV24: 21 compressors max.- MCV8: 7 compressors max.

Crystal hardware INT-IP A

INT-IP B

- 1 GIP6 board: 28 comp. max.- 2 GIP6 boards: 56 comp. max.- 1 GIP6A board: 7 comp. max.- 2 GIP6A boards: 14 comp. max.- 1 GIP4-4 board (from R6.0): 30 comp.

max.- 2 GIP4-4 boards (from R6.0): 60 comp.

max.- 1 GIP4-1 board (from R6.0): 8 comp. max.- 2 GIP4-1 boards (from R6.0): 16 comp.

max.

In some cases, depending on the devices communicating, voice (RTP flow) does not transitvia the Media Gateways. When two devices use the same compression algorithm, RTP flowmay be direct. Only the signaling is processed by the PCXs (see module Direct RTP innetwork - Detailed description).

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In the above figure, the voice flow between the two IP-Phones does not transit via the MediaGateways, but is directly routed between the terminals.

In the same way, as of R7.0, the voice flow between an Alcatel VoIP device and an H.323terminal or between two H.323 terminals can also be set up in direct mode.

2.4 Modem/Fax/Data Calls

As well as voice calls, the following types of call are possible:

- Group 3 fax calls using Fax Relay over IP.Two protocols are used:

• Proprietary T.38 protocol for calls between OmniPCX 4400 or Alcatel-Lucent OmniPCXEnterprise CS nodes

• Standard T.38 protocol for fax over IP calls with non-Alcatel-Lucent OmniPCXEnterprise CS H.323 gateways, such as the OmniPCX Office, and H.323 and SIPterminals from other manufacturers

Maximum speed for fax relay over IP calls is 9600 bits/s. For more information, see:module Fax over IP - Overview.

- From R5.1.2, transparent modem/fax/data calls between INT-IP/GA/GD boards (see themodule Modem, fax and data transparency over IP - Overview):

• Within the same node (or the same domain) for transparent modem/fax calls.

• Over an entire ABC network for transparent data calls.

Note:

If transparent modem/data calls are enabled (configuration option), fax relay calls between INT-IP/GA/GD

boards cannot be made. However, calls with H.323 devices are still made in fax relay mode.

2.5 Quality of Service

As the IP network supports both voice and data devices, mechanisms have been developed togive precedence to voice frame transfer (voice frames must be transferred in real time) overdata frame transfer and to separate voice and data flows.

Such mechanisms are defined by the following standards:

- 802.1p: Specifies the marking of level 2 frames of the ISO model to enable IP devices toprocess them according to the desired priority. High priority frames (voice) are processedby level 2 devices before low level frames (data).

- 802.1Q: Allows a VLAN (Virtual LAN) number to be configured to separate voice flowsfrom data flows. The principle used is to configure two separate VLANs, one containingVoIP devices and the other data devices. Each VLAN domain represents a broadcastdomain. For example, a broadcast message transmitted by an IP-Phone is only broadcastwithin the IP-Phone's VLAN and will not be received by data devices (PCs) as thesebelong to a different VLAN.

- Diffserv: Allows a priority level to be assigned to level 3 frames of the ISO model.

For more information on configuring Quality of Service, see the module 802.1p/Q and VLAN -Overview.

2.6 Connection of the Com Server with the Media Gateways

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In the case of a Com Server on a CS board or Appliance Server, the link with the Media

Gateways is over IP. From the Com Server side, there is an inter-shelf link over IP, the ComServer being the main shelf (shelf 0) and the Media Gateway being the peripheral shelf.

On a Common Hardware IP Media Gateway, the link is established on the GD board (rackcontroller board).

On a Crystal IP Media Gateway, the link is established on an INT-IP B or IOIP board. Theremay be one or two INT-IP B boards: one in the main (active) position and the other in thebackup position.

A Com Server hosted on a CPU5, CPU6, or CPU7 (from R6.0) board is linked with the boardsof the main ACT via C1 link, and a group of shelves may be connected via a wired link (RT2,INTOF). There may also be remote Crystal or Common Hardware IP Media Gateways over IP(see module Topology - Overview).

2.7 The H.323 Gateway Function of the Alcatel-Lucent OmniPCXEnterprise CS

A gateway is used to interconnect two networks using different protocols, e.g. an IP networkand a telephone network behind the PCX.

The H.323 gateway function of the Alcatel-Lucent OmniPCX Enterprise CS allows:

- An IP link to be set up between two PCXs on the same ABC network.

- Another H.323 gateway to be reached (for example: the IP board of an OmniPCX Office orthe H.323 gateway of another manufacturer).

- An H.323 terminal to be reached.

Important:

- In releases R5.1.1 and lower, the H.323 gateway function only supports voice and fax calls

(proprietary fax and T38 fax). Data calls (modem, TA and minitel) are not supported.

- From R5.1.2, ABC links over IP support transparent data calls.

The H.323 gateway function is ensured by GA, GD, and INT-IP A boards. Exchanges areperformed in compliance with the H.323v2 standard.

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H.323 calls are made using the E164 numbering scheme (standard dialing). E164 numbersare translated into IP addresses, either:

- Internally on the PCX, via speed dialing numbers.

- Or, by using a gatekeeper, that may be external or internal to the PCX.

For more information about:

- How to configure a link over IP, see the module ABC link through IP - Overview.

- How to declare an H.323 terminal and a gatekeeper, see the module H323 : terminals,gateway, gatekeeper - Detailed description.

2.8 Alcatel-Lucent IP-PhonesThere are several families of Alcatel-Lucent IP-Phones:

- IPTouch sets:

• Alcatel-Lucent IP Touch 4008 Phone (from R7.1): see module IP Touch 4008/4018Phone - Hardware description

• Alcatel-Lucent IP Touch 4018 Phone (from R6.1): see module IP Touch 4008/4018Phone - Hardware description

• Alcatel-Lucent IP Touch 4028 Phone (from R6.1): see module IP Touch4028/4038/4068 Phone - Hardware description

• IP Touch 4038 (from R6.0): see the module IP Touch 4028/4038/4068 Phone -Hardware description.

• IP Touch 4068 (from R6.0): see the module IP Touch 4028/4038/4068 Phone -Hardware description.

- Mobile IP Touch (MIPT) sets:

• Alcatel-Lucent Mobile IP Touch 300: see module Wireless LAN - Mobile IP Touch(MIPT) Sets

• Alcatel-Lucent Mobile IP Touch 600: see module Wireless LAN - Mobile IP Touch(MIPT) Sets

- IP-Phones V2 (e-Reflexe sets):

• A4010-IP: see the module 4010 IP set - Hardware description.


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- IP-Phones V1 and V1S: an UA3G (4020 or 4035) set combined with a TSC-IP V1 orTSC-IP V1S adapter (see the module TSC-IP V1 (4098RE) - Hardware description and themodule TSC-IP V1S (4098FRE) - Hardware description).

table 2.4: Alcatel-Lucent IP-Phones

Type of IP-Phone Set name

IP Touch

Alcatel-Lucent IP Touch 4008 Phone





Mobile IP Touch (MIPT)Alcatel-Lucent Mobile IP Touch 300

Alcatel-Lucent Mobile IP Touch 600

IP-Phones V2 (e-Reflexe)

A4010-IP

A4020-IP

A4035-IP

IP-Phones V1SA4022F (A4020+TSC-IP V1S)

A4037F (A4035+TSC-IP V1S)

IP-Phones V1A4022 (A4020+TSC-IP V1)

A4037 (A4035+TSC-IP V1)

For more information on using Alcatel-Lucent IP-Phones, see the module IP-Phones -Overview.

2.9 Configuring IP Devices

All IP devices have IP settings: IP address, subnetwork address, router address.

These settings can be configured:

- Dynamically: the settings are automatically assigned by a DHCP server: used forIP-Phones, for example.

- Statically: the settings are entered manually: used (for example) for a GD board, alwaysused for a GA board (the settings are assigned by configuring the board on the PCX).

The DHCP server is a device on which are configured the IP address ranges available todevices requesting them and other information (e.g. TFTP server address) used to initializedevices.

The DHCP server may be:

- External: for example, a DHCP server on a Windows PC (NT4 or 2000).

- Internal: the Com Server has its own DHCP server, that may be enabled or disabled (seethe module DHCP server - Detailed description).

table 2.5: Alcatel IP Equipment Configuration (Dynamic/Static)

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1In back up mode only

Dynamic configuration Static configuration

GD board Yes Yes (by V24, UA set or telnet)

GA board No Yes (by configuring board Ethernetsettings)

INT-IP B Yes Yes (by V24)

INT-IP A No Yes (by configuring board Ethernetsettings)

IP-Phones Yes Yes (via the set supervisor menu atinitialization)

2.10 Summary Table

table 2.6: Implementation of the Different Functions by PCX Components

ComServer

OmniPCX MediaGateway

ACT Media Gateway

GA GD INT-IP A INT-IP B

H.323 Gateway (internode linkand link to H.323 equipment)

x x x

SIP Gateway x

Signaling transfer for IP-Phones x x1

IP compression for H.323, SIP,and IP-Phones

x x x x

Remote IP link x x x x

Transparent modem/data (fromR5.1.2)

x x x x

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3.1 Document Purpose

This document describes the different parameters used to restrict VoIP calls to match networkbandwidth.

3.2 Call Admission Control on the Same Node.

Object name: IP Domain, attribute: Domain Max Voice Connection

This parameter is used to restrict the number of calls between devices on the same node.

Communications taken into account by Call Admission Control are:

- Communications between legacy sets (i.e. IP phones and/or compressors on IP boards)

- As of R6.1, communications between a legacy set and a SIP set

- As of R7.1, if the option is enabled, communications between two SIP sets: see moduleSIP - Call Admission Control (CAC)

Note:

Up to R7.0, all communications between a legacy set and an H.323 or SIP set are considered as extra-

domain call. As of R7.1, the IP domain of H.323 and SIP sets is taken into account.

Example: a remote Media Gateway is accessible via a 128 kbit/s leased link. In order tomaintain acceptable call quality, we want to restrict the number of calls to two on the link. To

do this:- In domain 1 parameters, extra-domain calls are restricted to 2.

- In domain 0 parameters, the parameter is left at -1 (no control)

Figure 3.1: Restricting the number of extra-domain calls

3.3 Restriction by Configuring IP Boards

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Object name: Shelf > Board, attributes: No. of Compressors for Gateway and No. of

Compressors for IP Devices

These two parameters are used to assign certain board compressors to the Gateway H.323function and others to calls to IP-Phones and Media Gateways.

Example: to take into account the bandwidth of the link between nodes 1 and 2, the number ofcalls is restricted to 5. On the boards which support the logical link, the maximum number ofcompressors for the gateway function is configured at 5.

Figure 3.2: Assigning compressors on IP boards

Restrictions:- If "direct RTP in network" is enabled, compressor allocation is dynamic and call restriction

on the logical link cannot be performed using these two parameters. In this case, the sumof the two parameters defines the total number of compressors that can be simultaneouslyused on the board.

- If the same board supports links to several nodes, the restriction can only be appliedglobally to outgoing calls from a node and not according to direction.

Caution:

The time slots of the IP trunk group T0/T1/T2 access must never be modified.

3.4 Restricting Calls by VPN Overflow

Object name: Inter-Node Links > VPN Overflow, attribute: Maximum number of IP calls

See also the module VPN overflow - Detailed description § Limiting VPN calls.

The maximum number of IP calls on a VPN hop may be configured to restrict the number ofcalls between two given nodes as inter-node calls are performed by VPN overflow.

Example: with 3 nodes interconnected by ABC links on IP.

Between the node 1 network and the node 2 network, the IP link is restricted to 5 calls.

Between the node 1 network and the node 3 network, the IP link is restricted to 10 calls.

There is no direct IP link between the IP networks of nodes 2 and 3.

To take into account these constraints, the number of calls on the logical links is restricted by

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configuring the maximum number of calls by VPN hop, as shown in the figure below.

Figure 3.3: Restricting calls by VPN overflow

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4.1 A

10Base T A variant of Ethernet, connecting stations via twisted pair cabling (shielded or unshielded) wiring at10Mbps.

10Base F A variant of Ethernet which runs on optical Fiber (mono-mode or umti-mode) at 10 Mbps.

100Base TX A variant of Ethernet which runs on Category 5 unshielded twisted pair wiring at 100Mbps. This is one ver-sion of Fast Ethernet.

100Base FX A variant of Ethernet which runs on optical Fiber (mono-mode or multi-mode) at 100 Mbps.1000Base T A variant of Ethernet, connecting stations via twisted pair cabling at 1 Gigabit.

1000Base LX A variant of Ethernet, connecting stations via Long-wawe optical fiber at 1 Gigabit

1000Base SX A variant of Ethernet, connecting stations via Short-wawe optical fiber at 1 Gigabit

802.x The set of IEEE standards defining LAN protocols

AALATM Adaptation Layer Corresponds to a service-dependant sublayer of the dala-link layer. The AAL ac-cepts data from different applications and provides it to the ATM layer in 48 bytes payload segments. AALsdiffers depending on the service required : e.g Constant Bit Rate or Variable Bit Rate. The ITU recom-mends four types of AALs : AAL1, AAL2, AAL3/4, AAL5.

AAL1ATM adaptation layer 1 used for connection oriented, delay-sensitive service requiring constant bit rate likevoice.

ACELP Algebraic-Code-Excited Liner Pediction Analog to digital coding providing good voice quality at only 8 kb/s.Has been standardized by the ITU in G729 as CS-ACELP.

Access Control Method This is the main distinguishing feature between different LAN technologies. It regulates each workstation'sphysical access to the cable (transmission medium), and determines the order in which nodes gain accessso that each user gets efficient service. Access methods include token passing, which is used in token ringand FDDI, and Carrier Sense Multiple Access with Collision Detection (CSMA/CD), which is employed by

Ethernet and Fast Ethernet.ACLAccess Control Lists Rules for packet filters (typically routers) that define which packets to pass and whichto block.

Access Router A router that connects your network to the external Internet. Typically, this is your first line of defenseagainst attackers from the outside Internet. By enabling access control lists to this router, you'll be able toprovide a level of protection for all of the hosts « behind » that router, effectively making that network aDMZ instead of an unprotected external LAN.

ADPCM Adaptative Differential Pulse Code Modulation Analog to digital coding providing high-quality digital signalsat 32 kb/s or 16 kb/s.

ADSL

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Asymmetric Digital Subscriber Line By using the latest technology in DSP, bitrates of over 8 Mb/s

(downstream) and 800 Kb/s (upstream) are possible over the existing telephone network. The telephonetraffic and the Internet traffic are separated by a filter allowing simultaneous use of the telephone and theInternet service.

AH Authentication Header Part of the IPSec protocol suite. It is the header used in IPSec-compliant IP packetsto carry authentication data permitting verification of the sending party.

ANT ADSL Network Termination (ADSL Modem)

Application-Level Firewall A firewall system in which service is provided by processes that maintain complete TCP connection stateand sequencing. Application level firewalls often re-address traffic so that outgoing traffic appears to haveoriginated from the firewall, rather than the internal host.

ARP

Address Resolution Protocol Used to translate an IP address to an ethernet physical address.ARPA : Advanced Research Project Agency

ASP Application Service Provider

ATM Asynchronous Transfer Mode A high speed, connection-oriented switching and multiplexing technology fortransmitting information across a WAN or a LAN. ATM divides information into fixed-length cells of 53 bytescapable of transmitting different types of traffic simultaneously, including voice, video, and data. Fixed-length cells allows cell processing to be done by the hardware, thereby reducing transit delays.

4.2 B

Backbone LAN or WAN connectivity between subnets across a high-speed network. Fiber optic cable is often used.

BACP Bandwith Allocation Control Protocol Is the associated control protocol for BAP.

Bandwith reservation Process of assigning or allocating bandwith to users or applications in a network based on priority in orderto make the best use of available bandwith.

BAP Bandwith Allocation Protocol Can be used to manage the number of links in a multi-link bundle. BAPdefines datagrams to coordinate adding and removing individual links in a multi-link bundle, as well as spe-cifying which peer is responsible for various decisions regarding managing bandwith during a multi-link con-nection.

BAS Broadband Access ServerBastion Host A system that has been hardened to resist attack, and which is installed on a network in such a way that itis expected to potentially come under attack. Bastion hosts are often components of firewalls, or may be «outside » web servers or public access systems.

BGP Border Gateway Protocol BGP4 is a replacement for older EGP Based on RFC 1771

BOD Bandwith on Demand

BOOTP Like DHCP, BOOTP provides an IP address to a client and also a file name in order to boot with TFTP.

BRAS

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Broadband RAS (idem as BAS)

BRI Basic Rate Interface ISDN interface composed of two B channels and one D channel. A throughput of up to128Kb/s is possible.

Broadcast A service in which information is sent from a central source to multiple destinations.

4.3 C

Cable modem Via the cable network, bitrates up to 10Mb/s (downstream) and 28..768 Kb/s (upstream) are possible.

CAR Commited Access Rate CAR, a function of CISCO « switch routers », allows static banwith management bylimiting the amount of bandwith consumed on a link by any given application . Provides a minimum or a

maximum bandwith for a specific type of traffic flow.CAS Channel Associated Signaling A type of in-band trunk signaling.

CBQ Class-Based Queuing Is a public-domain scheme which divides all user traffic into categories and assignsbandwith to each class. The classes themselves can be established by configuring CBQ by combinations ofIP address, protocols such as TCP or UDP and ports that represent the applications such as file transfer,Web access and so on.

CCP Compression Control Protocol

CCS Common Channel Signaling A type of out-of-band trunk signaling (for example, using Primary Rate Inter-face) in which a control channel carries signaling for separate voice and data channels. In CCS signaling is

passed in messages.CDDI Copper Distributed Data Interface

CELP Code –Excited Linear Prediction An analog to digital voice coding and compression scheme used in trans-mission of voice over data networks.

CGI Common Gateway Interface

CHAP Challenge-Handshake Authentication Protocol Is a more secure procedure for connecting to a system thanthe PAP. It avoids the password to be sent over the link as in PAP.

CIDR Classless Inter-Domain Routing Based on RFC 1519

CIR Commited Information Rate Average rate of information transfer a subscriber (for example the network ad-ministrator) has stipulated for a Frame Relay PVC.

Circuit Switching A method of communication whereby a circuit is held open and maintained only while the sender and recipi-ent are communicating. This is different from a dedicated circuit which is held open regardless of wetherdata is being sent or not, and different from a datagram / connectionless network, in which data flowswithout establishing a connection.

CLNS Connection Less Network Services This type of service allows information to be transferred over a networkwithout having to set up and end-to-end connection before information is sent.

CODEC

4-3



Coder-decoder Technique of transforming analog voice into a digital bitstream and vice versa; also used to

indicate the compression type (for example, G.729 CODEC).CONS Connection Oriented Network Services A connection-oriented service in a network is one in which a con-nection has to be set up between the source and destination before the communication can proceed.COPS Common Open Policy Services Being standardized by the IETF, aims to manage multiple network equip-ments from a central policy server.

CoS Class of Service In the 802.1p specification, COS uses 3 bits in the LAN frame header to assign seven pri-ority levels to LAN frames. Cos levels can be mapped to IP type of service (ToS) levels or supported inrouters with a number of other mechanisms.

CPE Customer Premises Equipment Is the end-user's home equipment. It can concern residential users or cor-

porate users.CSMA/CD Carrier Sense Multiple Access with Collision Detection A contention-based network access method in whichany computer may attempt to communicate at any time. Since there is no centralized force controlling themedium, a device must first sense wether or not the medium is in use. If the medium is unused, the devicethen transmits. If two computers sense that a channel is open and transmit at the same time, the result is acollision, after which there is a random pause determined individually by each transmitting machine. Eachmachine then senses the line again and, if it is available, retransmits.

CRC Cyclic Redundancy Check Error checking technique

CRM Customer Relationship Management

CRTP

Compression for RTPheader CRTP is a hop by hop compression similar to TCP header compression.CRTP reduces the IP/UDP/RTP header to 2-4 bytes.

4.4 D

Datagram A form of packet switching in which the packets that make up a conversation do not all take the same paththrough the network, thus improving the robustness and security of the network.

DES: Data Encryption Standard A symetric encryption algorithm. DES uses a 56-bit key. DES has the advantage that is is easily implemen-ted in hardware but its keyspace may not be large enough for continued use.

DHCP Dynamic Host Configuration Protocol DHCP offers dynamic configuration of IP address and related inform-

ation (subnet mask, default router,…). It is an extension of Bootp. DHCP provides safe, reliable, and simpleTCP/IP network configuration, prevents address conflicts, and help conserve the use of IP addressesthrough centralized management of address.

Diffserv Differentiated Services Basically, the idea is to assign different priorities to different flows based on theirQuality of Service needs. To achieve this, the differentiated service approach employs a small, well-definedset of building blocks from which a variety of services may be built. In particular, a small bit-pattern in eachIP packet, in the Ipv4 TOS (the Type Of Service byte has been redefined as the DS byte) byte is used tomark a packet to receive a particular forwarding treatment, or per-hop behaviour, at each network node.

DLC Data Link Control

DMZ

Chapter 4

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Demilitarized Zone A demilitarized zone is a computer host or small network inserted as a neutral zone

between a company's private network and the outside public network. It prevents outside users from gettingdirect access to a server that has company datas. Typically, a DMZ is an IP network segment that containsresources available to Internet users such as Web servers and FTP servers.

DNS Domain Name Service Domain Name System Is the way that Internet Domain names are located andtranslated into IP addresses. A domain name is a meaningful and easy-to –remember « handle » for an In-ternet address. The Internet user's PC contacts the DNS server which is located at the ISP premises.

DSLDigital Subscriber Line A protocol that can carry digital signals at a higher rate across twisted-pair cabling.

DSLAM DSL Access Multiplexer

DTE Data Terminal Equipment

DTMF Dual-Tone Multifrequency

Dual Homed Gateway A dual homed gateway is a system that has two or more network interfaces, each of which is connected toa different network. In firewall configurations, a dual home gateway usually acts to block or filter some or allof the traffic trying to pass between the networks.

DWDM Dense Wawelength Division Multiplexinhg

4.5 E

E1Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 2.048

Mbps using 30 64-Kbps digital channels for voice or data, plus a 64-Kbps channel for signaling and a64-Kbps channel for framing. E1 lines can be leased for private use from common carriers.

E.164 The ITU-T recommendation for assignment of international telecommunication numbering, which is an evol-ution of traditional telephone numbers.

EGP Exterior Gateway Protocol

EIR Excess Information Rate

Encapsulation The technique used by layered protocols in which a layer adds header information to the protocol data unit(PDU) from the layer above.

Encryption The process of converting information from an easily understandable format (plain text) into apparent ran-dom gibberish (ciphertext) by the use of well-defined rules and calculations known as algorithms or cipherto ensure the privacy and confidentiality of information. The reverse process is decryption.

Ethernet The most common layer-two protocol used in LAN's. Ethernet is a 10Mbps CSMA/CD standard originallydevelopped by Xerox to run on thick coaxial cabling. It has evolved and now runs primarily on twisted paircabling.

ESP Encapsulating Security Payload Payload format used in IPSec compliant IP packets to carry encrypted and/ or authenticated data, thereby preventing sniffing on the network between communicating nodes.

ETSI European TelecommunicationS Standard Institute

4-5



Extranet

An Extranet is an intranet which has been extended to include a company's suppliers, partners and custom-ers. They will lay the foundations for a major expansion of electronic commerce.

4.6 F

FAQ Frequently Asked Questions

FDDI Fiber Distributed Data Interface

FEC Forward Error Correction

Firewall A firewall is a set of related programs, located between the intranet and the Internet, that protects the re-

sources of a private network from users and/or from other networks. This firewall grants people from thecompany access to the Internet, but prevents that people from the Internet get access to the companies re-sources. In particular, a H323 firewall is very complex, because it allows H323 connections to be made(signaling and RTP/RTCP connections) between a component located on the private network and anotherone connected to the Internet or other network, in order to provide for example VoIP public connection.

FoIP Fax over IP is a service enabling standard G3 fax machines to communicate over the IP packet network in-stead of the PSTN.

FR Frame Relay An ITU standard for the interface to a public frame-switching network designed to providehigh-speed frame transmission with minimum delay across the wide area. It operates at data-link layer leveland handles multiple virtual circuits using HDLC encapsulation between connected devices. Is used in pub-lic and private networks, gradually replacing X25 and leased-line networks.

FRAD Frame Relay Access Device

Frame A variable-length layer-two protocol entity containing address and other control information, plus data.

FTP File Transfer Protocol Is a standard protocol within the TCP/IP protocol suite, which is the simplest way toexchange files between computers.

4.7 G

Gatekeeper The gatekeeper is an optional element. However, if a gatekeeper is present, it is mandatory that H323 end-points (terminals, gateways, MCU) make use of the services offered by gatekeepers. Basically, the gate-keeper is a kind of andpoint manager. The gatekeeper services basically include address translation, ad-mission control, bandwith control and zone management. It can be also in charge of theH323 call signalingacting as a call signaling « proxy » for the terminals.

Gateway In an internetworking context, the gateway can provide many services, including translation between signal-ing procedures or between codecs ; in such a case, it will perform call set-up/release and call control onboth the IP side and the other.

G.711The recommendation G.711 from the ITU is based on PCM technique at a sampling rate of 8kHz. The fre-quency bandwith that is used is 300Hz- 3.4 kHz. This is generally used in speech coding to restrict cap-tured bandwith to a factor where voice signals are mainly present. Each sample is coded with 8 bits(inEurope) or with 7 bits(in the US), which produces respectively a 64kbps or 56kbps bit stream.

Chapter 4

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G.723.1

The G723.1 recommendation targets very low bit rates. G723.1 is a dual rate coder (5.3kbps or 6.4kbps)based on ACELP for the low-rate coder and based on MP-MLQ for the high rate coder. The bandwith is3.1kHz in both cases. The lower bit rates has smaller quality than the higher one but provides systems de-signers with additional flexibility.G729a The G729a recommendation targets very low bit rate. This is one of the most recent and promising codecsstandardized by the ITU. This belongs to the G729 family. As such, this is a competitor to G723.1. This isbased on CS-ACELP and produces a 8 kbps bit stream from a 3.1 kHz bandwith. The bit rate is slightlyhigher than G723.1, but the delay is significantly lower.

GIF Graphics Interchange Format

GRE Generic Routing Encapsulation

GSM Global System for Mobile

4.8 H

H225 Performs the signalling for call control. Defines a much larger set of capabilities than those used in systemsconcerned only with voice traffic. H225 itself uses messages defined in H245 to establish and terminate in-dividual logical channels for audio. H225.0 corresponds to the RAS signaling function (see H323 RAS).

H235 Securisation and authentication of recording sequences for H323 Gatekeeper.

H323 An ITU standard for multimedia communication (voice, video and data) over connectionless networks that

do not provide a guaranteed quality of service such as IP based network. It addresses call control, mediamanagement, and bandwith management for point-to-point and multipoint conferences. It refers to a set ofother standards (H.245, H.225.0, and Q.931) to describe its actual protocol.

H323 RAS Registration, admission, and status. The RAS signaling function performs registration, admissions, band-width changes, status, and disengage procedures between the VoIP gateway and the gatekeeper.

H450 This corresponds to the supplementary services associated to H323 version 2 (similar to QSIG).

HDLC High-Level Data Link Control A bit-oriented synchronous data-link layer protocol developed by ISO. HDLCspecifies a data encapsulation method on synchronous serial links using frame characters and checksums.

HTMLHypertext Markup Language. A form of page description language used in the World Wide Web.

HTTP Hypertext Transfer Protocol Is the set of rules for exchanging files (text, graphic images, sound video, andother multimedia files) on the Web. Relative to the TCP/IP suite of protocols, HTTP is an application pro-tocol.

HTTPS Is a Web protocol developped by Netscape and built into many browsers that encrypts and decrypts userpage requests as well as the pages that are returned by the Web server. HTTPS is really just the use of theSecure Socket Layer as a sublayer under the regular HTTP application layer.

Hub The center of a star topology network or cabling system. Typically used in older Ethernet and token ringnetworks. A device connected to a hub receives all the transmissions of all other devices connected to thathub. Hubs are now being replaced in many cases by LAN switches.

4-7



4.9 IIAD Integrated Access device

IAP Internet Access Provider The IAP is responsible for the access between the user and the ISP. Towards theuser, the IAP can use for example the PSTN or ADSL. Towards the ISP, the typical network can be thePSTN or Frame Relay. When a user connects to an IAP, it is up to the IAP to find out to which ISP the userbelongs.

ICMP Internet Control Message Protocol Is the error and control message protocol used by the Internet protocolfamily. In particular, ICMP manages the ECHO/REPLY message (ping).

IDRP

Interdomain Routing ProtocolIEEE Institute of Electrical and Electronics Engineers

IEEE 802.1p An IEEE standard for prioritizing time-critical flows and filtering multicast traffic to contain traffic in layer-twonetworks. The 802.1p header includes three bits for prioritization, allowing for eight priorities to be estab-lished.

IEEE 802.1Q An IEEE standard for providing a virtual LAN capability within a campus network, used in conjunction withIEEE LAN protocols such as Ethernet and token ring.

IEEE 802.2 A data link standard outlining how basic data connectivity over cable should be set up. Used with the IEEE802.3, 802.4 and 802.5 standards.

IEEE 802.3 The IEEE's specification for Ethernet, including both physical cabling and layer-two protocol.

IEEE 802.3ad Specifies link aggregationIEEE 802.4 Specifies the Tken Bus protocol

IEEE 802.5 Specifies the Token Ring protocol

IEEE 802.11b Direct sequence standard for WLAN in the 2,4 GHz frequency range. Maximum throughput is 11Mbit/s

IETF Internet Engineering Task Force Task force consisting of over 80 working groups responsible for develop-

ing Internet standards.IGMP Internet Group Management Protocol Is used in case of multicast streams

IGP Internal Gateway Protocol

IGRP Interior Gateway Routing Protocol

IIS Internet Information Server

IKE Internet Key Exchange Part of the IPSec protocol suite. IKE is the current IPSec standard for SA rules ne-gotiation, key management and key exchange.

IMAP4

Chapter 4

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Internet Message Access Protocol 4 With IMAP, you view your e-mail at the server as though it was on

your client computer. An e-mail message deleted locally is still on the server. E-mail can be kept on andsearched at the server. Nethertheless, applications using IMAP sometimes include a synchronize functionto download new mails onto a PC and to upload new mails towards a mail-server.

Internet The Internet is a global information system constructed by interconnecting thousands of networks which arelogically linked by a global system of unique addresses based on the Internet protocol (IP). It supports com-munications using the TCP/IP suite in order to provide public or private high level services.

Intranet The term intranet refers typically to a corporate network which uses the same technology that is behind theInternet. Intranets can run over private WAN networks or public networks such as the Internet.

IP Internet Protocol The layer-three protocol used in TCP/IP set of protocols which support the Internet andmany private networks. IP provides a connectionless datagram delivery service for transport-layer protocols

such as TCP and UDP. IP provides also features for addressing, type-of-service specification, fragmenta-tion and reassembly, and security. IP is defined in RFC 791.

IPv4 Currently used IP version.

IP v6 the proposed next generation standard for IP addresses, incorporating IPSec security features and otheradditions. Ipv6 addresses are 128 bits wide.

IP addressing Each computer (known as a host) has at least one address that uniquely identifies it from all other com-puters on the Internet.IPv4 addresses are coded on 4 bytes.IP v4 addressing supports fives different network classes : - Class A : range 0.0.0.0 to 127.255.255.255 :for large networks - Class B :range 128.0.0.0 to 191.255.255.255 : for intermediate size networks - Class C

: range 192.0.0.0 to 223.255.255.255 : for small networks - Class D : range 224.0.0.0 to 239.255.255.255 :reserved for multicast groups - Class E : range 240.0.0.0 to 247.255.255.255 : reserved for future usePrivate adresses which are not routed by the Internet : - range 10. 0.0.0 to 10.255.255.254 - range172.16.0.0 to 172.31.255.254 - range 192.168.0.0 to 192.168.255.254

Unicast address the packet is addressed to only one host

Multicast address special type of address (hostid of all 1's). In this case all hosts connected to the network will accept thepacket.

IP Precedence IP Precedence allows three of the ToS bits in the IP header to be set with the values 0 through 7. This rank-ing determines the priority of the packet flow as it leaves one network for another, with 7 being the highestpriority.

IPCP IP Control Protocol Used within PPP, to negotiate for IP, the IP compression, IP address, etc …

IPSec Internet Protocol Security A set of extensions to IP adding security services. The suite consists of protocolsfor an authentication header (AH), encapsulating security payload (ESP) and a key management and ex-change protocol (IKE)

IP Spoofing An attack whereby a system attempts to illicitly impersonate another system by using its IP network ad-dress.

IPX Internetwork Packet Exchange NetWare network layer (Layer 3) protocol used for transferring data fromservers to workstations. IPX is similar to IP.

4-9



IS

Information SystemsISDN Integrated Services Digital Network A communication protocol offered by telephone companies that permitstelephone networks to carry data, voice, and other traffic.

ISAKMP Internet Security Association and Key Management Protocol A framework negotiation protocol on top ofwhich IKE is designed.

ISO International Standards Organization

ISP Internet Service Provider An ISP is a company which provides connectivity to the Internet and network ser-vices, most commonly for users who are accessing the Internet via the telephone network. Typical servicesare : access to the Web, e-mail, webspace for homepages, newsgroups

IT Information Technology

ITSP Internet Telephony Service Provider

ITU International Telecommunication Union An international body of member countries whose task is to definerecommendations and standards relating to the international telecommunications industry. The fundamentalstandards for ATM have been defined and published by the ITU (previously CCITT).

4.10 J

Jitter A short term timing deviation It'is one of the three major concerns when carrying Voice over IP. It corres-

ponds to the variation in the delay between packets.

4.11 K

4.12 L

L2F Layer 2 Forwarding Is a protocol that allows corporations to extend their own corporate network throughprivate « tunnels » over the public Internet. L2F is a proposed standard sponsored by CISCO systems.

L2TP Layer Two Tunneling Protocol Is a standard that combines the best features of two existing tunneling proto-

cols : CISCO's L2F and PPTP.LAC L2TP Access Concentrator

LAN Local Area Network A group of computers and other devices dispersed over a relatively limited area andconnected by a communication link that enables any device to interact with any other on the network. TheLAN corresponds to the network inside the enterprise.LANE LAN Emulation

LAP Link Access Protocol

LAP-B Link Access Procedure Balanced

Chapter 4

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LCP

Link Control Protocol Used by PPP for the negociation of the communication parameters : authenticationmethod, maximum receive unit,…

LDAP Lightweight Directory Access Protocol Protocol for access to directory services managed by a directoryserver. Informations about hosts, users (e.g. authentication, access information), traffic handling policy(QoS) can be managed by a directory server.

LLLeased Line

LLC Logical Link Control

LLC/SNAP : Logical Link Control / Sub-Network Access Protocol

LNS

L2TP Network Server

4.13 M

MAC Medium Access Control

MAC address The layer-two address of a LAN device

MAN Metropolitan Area Network

MAPI Messaging Application Programming Interface

MC Multipoint controller

MCU Multipoint Control Unit This aims at supporting conferences between three or more H323 endpoints. It mayhandle the media streams between end-points in a multi-cast approach.

MGCP Media Gateway Control Protocol

MIB Management Information Base

MLPPP Multi Link Point to Point Protocol Allows to use multiple independent channels (links) to create a virtualsingle bundle. Based on RFC 1990.

MIME

Multipurpose Internet Mail ExtensionsMOS Mean Opinion Score

MP-MLQ MultiPulse-Maximum Likelihood Quantization

MPLS Multi Protocol Label Switching Protocol being defined by the IETF to allow IP packets to be switched in anefficient manner using different types of link layer protocols (e.g. ATM). It is an optimization of the classicalIP routing. MPLS attaches « labels » to IP packets which enables routers and switches to forward trafficbased on information in the labels, rather than inspecting the different fields deep within each and everypacket.

MPOA

4-11



Multi Protocol Over ATM

MPPP Multi-link PPP It provides bandwith aggregation from multiple links, including analog and ISDN, to get ahigher communication throughput.

MTU Maximum Transfer Unit The maximum packet size, in bytes, that a particular interface can transmit. Ex-ample 1.5Kbytes bytes on Ethernet, 4 Kbytes on FDDI.

4.14 N

NAS Network Access Server NAS are devices composing a POP. They can be connected to different kind ofnetworks and interfaces such as PRI, BRI, ATM, Ethernet … A point-to-point connection is establishedbetween the Internet user and the NAS which will route the packets to the correct interface.

NAT Network Address Translation Is the translation of an IP address used within one network to a different IPaddress known within another network. Typically, a company maps its local inside network addresses toone or more global outside IP addresses and unmaps the global IP addresses on incoming packets backinto local IP addresses. It allows to share a single address between multiple equipments, and to connectthem all to the Internet at the same time.

NCP Network Control Protocol Used within PPP to negotiate the network protocol options.

NetBEUI Network Bios Extended User Interface In charge of transport functions (level 4 ofOSI model). Used in par-ticular in case of IBM PC networks.

NetBIOS Network Basic Input/Output System

NFS Network File System

NMC Network Management Centre

NNTP Network News Transfer Protocol Is the predominant protocol used by computers (servers and clients) formanaging the notes posted on Usenet newsgroups.

NTP Network Time Protocol NTP is a UDP-based protocol used for synchronizing a set of network clocks usinga set of distributed clients and servers. Implementation is based on RFC 1305. Simple NTP is documentedin RFC 2030.

4.15 OOSI Open Systems Interconnection

OSPF Open Shortest Path First Routing protocol based upon the Link State Algorithm Each router actively test thestatus of its link to each of its neighbors, send this information to its neighbors , which then propagate it.

4.16 P

Packet A packet is the basic unit of transmission under IP. Data streams are broken into packets by the transmit-ting machine, passed through the network and then reassembled at the receiving end.

Chapter 4

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Packet filtering

The ability of a bridge, router or gateway to limit propagation of packets between two or more interconnec-ted networks.

Packet switching A communications method in which variable-length packets are individually routed between hosts.

PAP Password Authentication Protocol Is a procedure used by PPP servers to validate a connection request.Passwords are sent in clear text without security and the originator can make repeated attempts to gain ac-cess. For these reasons a server that supports CHAP will offer to use that protocol before using PAP.

PAT Port Address Translation

Payload Refers to the portion of a packet following the header.

PCM

Pulse Code ModulationPDU Protocol Data Unit

PLC Packet Loss Compensation

PoP Point of Presence The node at which an ISP connects a subscriber to the Internet. To give individual ac-cess at the lowest rate possible, dial-in facilities (a POP) are installed by the Internet Service Provider (ISP)in every telephone area. A POP consists of one or more NAS.

POP3 Post Office Protocol version 3 Is the most recent version of a standard protocol for receiving e-mail. POP3is a client-server protocol in which e-mail is received and held for you by your Internet server. This protocolincludes commands to login, logout, fetch messages and deletes messages. The point of the POP is to

transmit the E-mails from the E-mail server towards the user s PC to be read later.Port Number Fields of the TCP and UDP header which identifies the source and destination application program . Iscoded on 2 bytes.

POTS Plain Old Telephone Set (System) The basic telephone service supplying standard single-line telephones,telephone lines, and access to the public switched telephone network.

PPP Point to Point Protocol An Internet protocol which is used to connect serial terminal devices, usually overdial-up lines. PPP (Point-to-Point Protocol) is a protocol for communication between two computers using aserial interface. PPP is a full-duplex datalink protocol that can be used on various physical media, includingtwisted pair or fiber optic lines or satellite transmission. It uses a variation of High Speed Data Link Control(HDLC) for packet encapsulation. The PPP protocol handles : error detection, support of multiple protocols

(IP, IPX, …), dynamic IP address, authentication of the user.PPPoAPPP over ATM

PPPoE PPP over Ethernet Primarily deployed in DSL environments. Allows authentication, control of the connec-tion in case of a connection to an ISP through Ethernet. PPPoE leverages existing Ethernet infrastructuresto allow users to initiate multiple PPP sessions within the same LAN.

PPTP Point to Point Tunneling Protocol Is a layer 2 tunneling protocol based on PPP that allows corporations toextend their own corporate network through private « tunnels » over the public Internet. PPTP is a pro-posed standard sponsored by Microsoft and other companies.

PQ

4-13



Priority Queuing

PRI Primary Rate Interface ISDN interface composed of 30 B channels and one D channel. A throughput of upto 2Mb/s is possible.

Proxy A software agent that acts on behalf of a user. Typical proxies accept a connection from a user, make a de-cision as to whether or not the user or client IP address is permitted to use the proxy, perhaps does addi-tional authentication, and then completes a connection on behalf of the user to a remote destination.

PSQM Perceptual Speech Quality Measurement

PSTN Public Switched Telephone Network

PVC Permanent Virtual Circuit

4.17 Q

QoS Quality of Service Quality of service means the ability of networks to guarantee and maintain certain per-formance levels for each application, according to the specified needs of each user. It will consist in a spe-cial type of treatment applied to a flow of traffic or for a certain user e.g. Regarding VoIP, Quality of servicewill help to reduce transit delay, jitter and ensure bandwith needs.

4.18 R

RADIUS Remote Authentication Dial-in User Service Is a client/server protocol based on UDP and software that en-

ables remote access servers to communicate with a central server to authenticate dial-in users and author-ize their access to the requested system or service. RADIUS provides a central location for storing informa-tions like : authentication attributes, configuration data for establishing a WAN connection for an incomingcall, dialout information, static routes and filters, accounting information, security information. Developpedto better manage large serial line and modem pools. The client/server model supports security via PAP,CHAP, UNIX login, and other authentication schemes, such as challenge/response systems.

RARP Reverse Address Resolution Protocol Used to translate an ethernet physical address into an IP address.

RAS Registration Admission and Status This is defined in H225.0. It performs registration, admission, bandwithchanges, status and disengage procedures between H323 endpoints of a zone and the gatekeeper re-sponsible for that zone.

RAS Remote Access Service/ServerRED Random Early Discard Method which relies on rules based on probability to instruct a router to begin drop-ping packets when established queuing thresholds are crossed.

RFC Request For Comment

RIB Routing Information Base

RIP Routing Information Protocol Based upon the Distance Vector protocol. Each router sends all or some por-tion of its routing table but only to its neighbors. Each router updates its routing table based on the vector ofthese distances (hop counts) that it receives from its neighbors.

Chapter 4

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Router

A layer-three device responsible for making decisions regarding which of several paths network traffic willfollow. To do this, it uses a routing protocol to gain information about the network, and algorithms to choosethe best route based on several criteria (known as routing metrics). Routers interconnect subnets.

RSAThe original and best-known asymmetric encryption scheme where one key (the public key) and one al-gorithm is used to encrypt data and another key (the private key) and another algorithm are used for de-cryption.

RSVP Resource reservation Protocol RSVP is a QoS signalling protocol for the Internet. It reserves a portion ofthe output link in each router along the path of a flow for a particular application. It delivers QoS requests toall nodes along the path (s) of the flows and establish /maintain state of the requested service. RSVP alsoincludes provisions for constraining packet delay and guaranteeing bandwith availability , but on a managedcorporate IP network, only the prioritization feature needs to be used. RFCs : 2210, 2209, 2208, 2207,

2206, 2205RTP/RTCP Real-time Transport Protocol / Real-time Transport Control Protocol This provides the media stream pack-etization and synchronization for all data networks.

4.19 S

SASecurity Association In the IPSec protocol suite, a dedicated secure virtual connection between two nodes.

SDH Synchronous Digital Hierarchy

Serial delay Serial delay results when a delay sensitive packet (voice in our case) is stuck in a buffer behind a packet

that has already begun to be sent. All links in a WAN operate in a serial manner.Thus the delay sensitive traffic must wait until the packet has passed. The delay variation introduced by thisserial delay depends on the maximum length of the packet (long packets results in less link overhead butmaximizes serial delay)Thus the delay sensitive traffic must wait until the packet has passed. The delay variation introduced by thisserial delay depends on the maximum length of the packet (long packets results in less link overhead butmaximizes serial delay)There are 2 ways to deal with serial delay : –the data size can be limited (Maximum Transmission Unit size)

– the speed of the link can be raised

SIP Session Initiation Protocol IETF standard for VoIP systems.

SLAService Level Agreement

SMTP SimpleMail Transfer Protocol SMTP is used by an E-mail server to transmit an E-mail to the destination E-mail server. In most cases, the user will use a PC to retrieve his/her mail from the server using usuallyPOP3 or IMAP.

SNASystems Network Architecture

SNMP Simple Network Management Protocol Is a protocol used for network management. The Network Manage-ment Center contains an SNMP-manager. The objects to be managed contain an SNMP-agent and a Man-agement Information Base (MIB). The manager can read from and write into this database. The agent canalso send 'traps' towards the manager to report alarms. Summarized, this protocol can be used to handleFault, Performance, Security and Configuration Management.

4-15



SSL

Secure Socket Layer Is a program layer created by Netscape for managing the security of message trans-missions in a network. It is used by secure protocols such as HTTPS.

STASpanning Tree Algorithm It's task is to construct a non-looping topology by deciding not to use certain of thelinks in the network.

Subnet A portion of a network in which all stations share a common subnet address.

Subnet Mask Used to subdivide a network into subnets. Defines the number of bits borrowed for the subnet address. Themask is 32 bits long. Example : 255.255.255.0Internet routers use only the network id of the destination address to route traffic to a subnetted environ-ment. Routers within the subnetted environment use the extended-network-id (network id + subnet id) toroute traffic between the individual subnets.

SVC Switched Virtual Circuit

4.20 T

T120 Data conference protocol

T30 Procedures for document facsimile transmission in the general switched telephone network

T37 Procedures for batch or Store and Forward Group 3 facsimile communication over IP networks. Built onTCP and SMTP.

T38 Procedures for real-time Group 3 facsimile communication over IP networks. Built on UDP in Fax relaymode.

TCP Transmission Control Protocol This is a reliable connection oriented protocol that allows the error free deliv-ery of a byte stream. Large packets are segmented into smaller ones and are resequenced at the final des-tination if necessary. Flow control makes sure that the receiving side is not overloaded.

TCP /IP The various protocols which support the Internet and many private networks.

Telnet Is the way you can access someone else's computer, assuming they have given you permission. With tel-net, you log on as a regular user with whatever privileges you may have been granted to the specific applic-ations and data on that computer.

TFTP Trivial File Transfer Protocol Is a protocol used to transfer files and has been implemented on top of UDP.In general, it is used to download binary and data files.

ToS Type of Service An 8-bit field within the IP header which can be used by the device originating the packet,or by an intermediate networking device, to signal a request for a specific QoS level. The ToS field is re-defined in DiffServ.

TTLTime To Live. The TTL indicates the maximum amount of time a diagram is allowed to remain in the net-work (usually, the maximum number of hops through routers).

Tunneling Tunneling is a technique whereby information is encapsulated in a protocol that allows the information topass through a larger stream of information without fear of interference. Effectively, « tunneling » creates a

Chapter 4

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secure means to transport information among other information. It is becoming a popular method of creat-

ing virtual private network interconnection over common media such as the Internet.Trafic shaping This applies at access devices to prevent a huge burst of traffic from congesting the backbone network.Shaping involves accepting a burst from an input device, buffering the traffic and then « smoothing » outthe flow so that the burst is distributed over a long period of time, a time period based on configurationparameters.

4.21 U

UDP User Datagram Protocol The UDP protocol is an unreliable connectionless protocol which is widely used forclient/server request/reply applications where the prompt delivery is more important than the accurate deliv-ery.

URLUniversal Resource Locator To retrieve an HTML page from a remote host, a user will enter a link in hisbrowser. This link is called a URL.

4.22 V

V.34/V.34bis V.34 is a standard, approved by the ITU, for transmitting data to modems. V.34bis provides up to 33.6kbpsof fallback to 31.2 kbps or V.34 transfer rates (28.8Kbps or fallback to 24 Kbps and 19.2 Kbps and back-wards compatibility with V.32 and V.32bis).

V.90 Is a standard approved by the ITU for transmitting data downstream to modems at 56Kbps. 56Kbps trans-mission technologies exploit the fact that most telephone company offices are interconnected with digital

lines.VAD Voice Activity Detection In Voice over IP (VOiP), voice activation detection (VAD)is a software applicationthat allows a data network carrying voice traffic over the Internet to detect the absence of audio and con-serve bandwidth by preventing the transmission of "silent packets" over the network.

VLAN Virtual Lan In a VLAN, individual devices are assigned membership in a group that has connectivity only toeach other and whose traffic does not mix with other traffic as it crosses backbone networks, distantswitches and shared hubs. Many of these groups or VLAN's may coexist on the same network infrastruc-ture. VLAN also allows to reduce the broadcast domain to the ports belonging to the VLAN. 802.1Qprovides virtual LAN capability whereas 802.1p provides prioritizing time-critical flows. The 802.1p headerincludes three bits for prioritization, allowing eight priorities to be established.

VoIP

Voice over IP Is the voice carrying on IP networkVPIM Voice Protocol over Internet Messaging

VPN Virtual Private Network A Virtual Private Network enables to send data between two hosts across a sharedor public internetwork (ex the Internet) in the same way as in case of a point-to-point private link. It corres-ponds to extend an Intranet (Home/remote workers or LAN-to-LAN connection)It gives the appearance and benefits of a private network, including continuous availability and reliability.VPN offers the following properties : –1encapsulation of the private data – authentication of the VPN con-nection to be established – data encryption to ensure the confidentiality of the data over non-secure net-worksA VPN uses a protocol like PPTP, L2TPor IPSec.

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VRPP

Virtual Router Redundancy Protocol

4.23 W

WAIS Wide Area Information System Is an application layer protocol which can be used to look for information ina large number of documents.

WAN Wide Area Network This corresponds to a network outside the business, and one that is accessible (suchas the Internet, and an Intranet Extension)

WFQ Weighted Fair Queuing WFQ applies to the bandwith an application receives on an output link :

– Traffic is assigned a priority – Priority influences which traffic is transmitted first on a congested pipe

It has no impact on a non-congested pipe.WINS Windows Internet Naming Service

WLAN Wireless LAN

WRED Weighted Random Early Discard Is a variation of RED. A pure RED router just randomly selects packets todrop when some buffer threshold is reached independently from the priority of the packet. WRED tries toidentify the low-priority traffic and randomly discard those packets when congestion occurs.

WWW World Wide Web A worldwide network of interconnected computer servers which allow users to access in-formation rapidly and easily via the Internet.

4.24 X

X25 ITU standard which was the first international standard for packet switching. Covers only the bottom threelayers of the OSI Model.

XMLeXtensible Markup Language

4.25 Y

4.26 Z

Zone A collection of H323 terminals, Gateways and MCUs managed by a single Gatekeeper.

Chapter 4

Documents

Alcatel-Lucent OXE Voice over IP.pdf