imaginar 7. p_protocolos_sobre ip

7/29/2019 Imaginar 7. P_protocolos_sobre IP

1/82

1

Protocolos sobre IP

Fausto Vasco


2/82

2

Objetivos

Queremos hacer una descripcin rpida de los protocolosde comunicaciones que ms influencian el mercadoactual: Frame Relay

X.25

MPLS

SIP

H323 NGN


3/82

3


4/82

4

X.25

X.25 is an ITU-T standard data link layer protocol for packetswitched WAN communication.

An X.25 WAN consists of packet-switching exchange (PSE) nodes asthe networking hardware, and leased lines, POTS connections orISDN connections as physical links.

X.25 is part of the OSI protocol suite, a family of protocols that wasused especially during the 1980s.

X.25 is today to a large extent replaced by less complex protocols


5/82

5

Addressing and virtual circuits

X.25 supports two types ofvirtual circuits: Switched Virtual Circuits (SVC) which are established as and when required

through a call establishment and clearing procedure

Permanent Virtual Circuits (PVC) which are preconfigured into the network.

VC may be established using X.121 addresses. The X.121 address consists of:

three-digit Data Country Code (DCC) plus a network digit, together forming thefour-digit Data Network Identification Code (DNIC),

followed by the National Terminal Number(NTN) of at most ten digits.

Note the use of a single network digit, seemingly allowing for only10 network carriers per country, but some countries are assignedmore than one DCC to avoid this limitation.

One DTE-DCE interface to an X.25 network has a maximum of4095 logical channels on which it is allowed to establish virtualcalls and permanent virtual circuits.


6/82

6

Architecture

The general concept of X.25 was to create a universal andglobal packet-switched network.

Much of the X.25 system is a description of the rigorous error

correction needed to achieve this, as well as more efficientsharing of capital-intensive physical resources.

The X.25 specification defines only the interface between asubscriber (DTE) and an X.25 network (DCE).

Replaced by Frame Relay is now considered an obsoleteprotocol.

X.25 was the base to new protocols like Frame Relay and

ATM which use extensively the Virtual Circuits.


7/82

7


8/82

8

An Efficient and Flexible WAN Technology

Frame Relay has become the most widely used WAN technology. primarily because of its price and flexibility.

Frame Relay reduces network costs by using less equipment, lesscomplexity, and an easier implementation.

With increasing globalization and the growth of one-to-manybranch office topologies, Frame Relay offers simpler networkarchitecture and lower cost of ownership.


9/82

9

The Frame Relay WAN

Frame Relay has lower overhead than X.25 because it hasfewer capabilities. Frame Relay does not provide error correction.

This is left to higher layers.

The Frame Relay node simply drops packets without notification whenit detects errors.


10/82

10

The Frame Relay WAN

Frame Relay handles volume and speed efficiently bycombining the necessary functions of the L2 and L3 into onesimple protocol.

As a data link protocol, Frame Relay provides: Access to a network, Delimits and delivers frames in proper order, and

Recognizes transmission errors through a standard CRC.

As a network protocol, Frame Relay provides: Multiple logical connections over a single physical circuit and

Allows the network to route data over those connections.

Frame Relay operates between an end-user device, such asa LAN bridge or router, and a network. Some networks use Frame Relay itself, but others use digital circuit

switching or ATM cell relay systems.


11/82

11

Virtual Circuits

The connection through a Frame Relay network between twoDTEs is called a virtual circuit (VC). There is no direct electrical connection from end to end.

The connection is logical.

With VCs, Frame Relay shares the bandwidth among multiple usersand any single site can communicate with any other single sitewithout using multiple dedicated physical lines.

There are two ways to establish VCs: SVC PVC


12/82

12

Local Significance

VCs provide a bidirectional communication path from onedevice to another.

VCs are identified by DLCIs.

Typically are assigned by the service provider. Local significance, which means that the values themselves are not

unique in the Frame Relay WAN.

Two devices connected by a VC may use a different DLCI value to

refer to the same connection.


13/82

13

Local Significance


14/82

14

Multiple VCs

Frame Relay is statistically multiplexed, meaning that ittransmits only one frame at a time, but that many logicalconnections can co-exist on a single physical line.

The router connected to the Frame Relay network may havemultiple VCs connecting it to various endpoints. Multiple VCs on a single physical line are distinguished because each

VC has its own DLCI.

Very cost-effective Each endpoint needs only a single access line and interface.

Average bandwidth requirement of the VCs, rather than on themaximum bandwidth requirement.


15/82

15

The Frame Relay Encapsulation Process

Frame Relay is a Layer 2 protocol. Frame Relay accepts a packet from a network layer protocol such as

IP.

It then wraps it with an address field that contains the DLCI and a

checksum.


16/82

16

Frame Relay Topologies

When more than two sites are to be connected, you mustconsider the topology of the connections between them.

Every network or network segment can be viewed as being one

ofthree topology types: Star (hub and spoke) full mesh, or

partial mesh.


17/82

17

Frame Relay Address Mapping

Before a router is able to transmit data over Frame Relay, itneeds to know which local DLCI maps to the Layer 3address of the remote destination.

This address-to-DLCI mapping can be accomplished eitherby: static mapping

By entering a static map

dynamic mapping. Inverse ARP.-The Frame Relay router sends out Inverse ARP requests on

its PVC to discover the L3 address of the remote device.


18/82

18

Local Management Interface (LMI)

The Frame Relay original design provides packet-switched datatransfer with minimum end-to-end delays.

The original design omits anything that might contribute to delay.

When vendors implemented Frame Relay as a separatetechnology rather than as one component of ISDN, they decided thatthere was a need for DTEs to dynamically acquire informationabout the status of the network. The original design did not include this feature.

A consortium of Cisco, DEC, Northern Telecom, and StrataComextended theFrame Relay protocol to provide additional capabilities for complexinternetworking environments.

These extensions are referred to collectively as the LMI.

Basically, the LMI is a keepalive mechanism that provides statusinformation about Frame Relay connections between the router(DTE) and the Frame Relay switch (DCE).


19/82

19

Local Management Interface (LMI)


20/82

20

LMI Extensions

LMI extensions are extremely useful in an internetworking environment.VC status messages

Informs PVC integrity by communicating and synchronizing betweendevices, periodically reporting new PVCs and the deletion of PVCs.

Prevent data from being sent into black holes (VCs that no longer exist).Multicasting

Multicasting supports the efficient delivery of routing protocol messagesand address resolution procedures that are typically sent to many

destinations simultaneously.Global addressing

Gives connection identifiers global rather than local significance

This makes the Frame Relay network resemble a LAN in terms of

addressing, and ARPs perform exactly as they do over a LAN.Simple flow control

Provides for an XON/XOFF flow control mechanism that applies to theentire Frame Relay interface.


21/82

21

LMI

The three possible PVC states are as follows: Active state Indicates that the connection is active and that routers

can exchange data.

Inactive state Indicates that the local connection to the Frame Relayswitch is working, but the remote router connection to the Frame Relayswitch is not working.

Deleted state Indicates thatno LMI is being received from the FrameRelay switch, or that there is no service between the CPE router and

Frame Relay switch.


22/82

22

Frame Relay Key Terminology

There are some key terms and concepts to learn:Access rate or port speed

The speed of the line is the access speed or port speed.

Access rate is the rate at which your access circuitsjoin theFrame Relay network. Port speeds are clocked on the Frame Relay switch.

It is not possible to send data at higher than port speed.

Committed Information Rate (CIR)

Customers negotiate CIRs with service providers for eachPVC.

The service provider guarantees that the customer can senddata at the CIR.

All frames received at or below the CIR are accepted.


23/82

23

Frame Relay Key Terminology

A greatadvantage of Frame Relay is that any network capacity that isbeing unused is made available or shared with all customers, usually atno extra charge.

This allows customers to "burst" over their CIR as a bonus.

Oversubscription

Service providers sell more capacity than they have on the assumptionthatnot everyone will demand their entitled capacity all of the time.

Because ofoversubscription, there will be instances when the sum of CIRs

frommultiple PVCs to a given location is higher than the port or accesschannel rate.

This can cause traffic issues, such as congestion and dropped traffic.


24/82

24

Paying for Frame Relay: Bursting

Frame Relay can allow customers to dynamically access this extrabandwidth and "burst" over their CIR for free.

Various terms are used to describe burst rates including the CommittedBurst Information Rate (CBIR) and Excess Burst Size (BE).

CBIR Is a negotiated rate above the CIR which the customer can use to transmit

for short burst. It allows traffic to burst to higher speeds, as availablenetwork bandwidth permits.

However, itcannot exceed the port speed of the link. The duration of a burst transmission is the Committed Time.

Frames submitted at this level are marked as Discard Eligible (DE).

BE

The BE is the term used to describe the bandwidth available above theCBIR up to the access rate of the link. BE, is not negotiated.

Frames may be transmitted at this level butwill most likely be dropped.


25/82

25

Paying for Frame Relay: Bursting


26/82

26

Frame Relay Flow Control

Frame Relay reduces network overhead by implementingsimplecongestion-notification mechanisms. Forward Explicit Congestion Notification (FECN)

Backward Explicit Congestion Notification (BECN).

Discard Eligibility (DE) bit, which identifies less important traffic thatcan be dropped during congestion periods.


27/82

27


28/82

28

Objectives

Describe Multiprotocol Label Switching (MPLS) features andoperation.

Identify the fields and format of an MPLS label.

Describe the purpose of the control and data planes in theMPLS architecture.

Describe the function and architecture of Label SwitchRouters (LSRs) and Edge LSRs.


29/82

29

WAN Topologies

With MPLS, a site requires only one connection to theMPLS SP. High-performance method for forwarding packets through a network.

Enables routers at the edge of a network to apply simple labels in the

form of numbers to these packets. Routers can then switch packets according to labels, incurring minimal

overhead for routing lookup.


30/82

30

Basic Mult iprotocol Label Switching (MPLS) Features

MPLS reduces routing lookups. MPLS forwards packets based on labels.

Labels usually correspond to IP destination networks (equal

to traditional IP forwarding). Labels can also correspond to other parameters:

Layer 3 VPN destination

Layer 2 circuit

Outgoing interface on the egress router

QoS

Source address

MPLS supports forwarding ofall Layer 3 protocols, not justIP.


31/82

31

MPLS Operation

Only edge routers must perform a routing lookup. Core routers switch packets based on simple label lookups

and swap labels.


32/82

32

Cisco IOS Platform Switching Mechanisms

Process switching, or routing table-driven switching: Full lookup is performed at every packet

Fast switching, or cache-driven switching: Most recent destinations are entered in the cache

First packet is always process-switched

Topology-driven switching: CEF (prebuilt FIB table)

incorporates the best of theprevious switching mechanisms.

CEFCEF

CEFCEF

Cisco Express Forwarding

Forwarding Information Base (FIB)


33/82

33

Standard IP Switching Overview

.

.

.


34/82

34

CEF Switching Overview

.

.

.


35/82

35

MPLS Switching Overview

Edge LSR

MPLSIP

R1

Edge LSR

R3 LSRR2 LSR

R6

Edge LSR

Station A Station B

IP Domain

L

LabelInstructions

Internal Table

LSR

MPLSMPLS

R4 LSR R5 LSR


36/82

36

MPLS Characteristics

MPLS technology is intended to be used anywhere, regardless of Layer 1 media and Layer 2 protocol.

MPLS uses a 32-bit label field that is inserted between Layer 2and Layer 3 headers (frame mode MPLS).

MPLS over ATM uses the ATM header as the label (cell modeMPLS).


37/82

37

Label Format

Field Description

20-bit label The actual label. Values 0 to 15 are reserved.

3-bit experimental (EXP)field

Undefined in the RFC. Used by Cisco to define a class ofservice (CoS) (IP precedence).

1-bit bottom-of-stack

indicator

MPLS allows multiple labels to be inserted. The bottom-

of-stack bit determines if this label is the last label in thepacket. If this bit is set (1), the setting indicates that thislabel is the last label.

8-bit Time to Live (TTL)

field

Has the same purpose as the TTL field in the IP header.

Label Stack


38/82

38

Label Stack

PID in a Layer 2 header specifies that the payload starts with alabel (or labels) and is followed by an IP header.

The bottom-of-stack bit indicates whether the next header is

another label or a Layer 3 header. Receiving router uses the top label only.


39/82

39

Frame Mode MPLS Operation

Note:The type or protocol ID field indicates as MPLS enabled layer-3 protocol.


40/82

40

Major Components of MPLS Architecture

Control plane: Exchanges routing information and labels

Contains complex mechanisms, such as OSPF, EIGRP, IS-IS, and BGP,to exchange routing information

Exchanges labels, such as LDP, BGP, and RSVP

Data plane: Forwards packets based on labels

Has a simple forwarding engine

Control Plane Components Example


41/82

41

Control Plane Components Example

Information from control plane is sent to the data plane.

Label Switch Routers (LSRs)


42/82

42

Label Switch Routers (LSRs)

LSR primarily forwards labeled packets (swap label).

Edge LSR:

Labels IP packets (impose label) and forwards them into the MPLS domain. Removes labels (pop label) and forwards IP packets out of the MPLS domain.

Functions of LSRs


43/82

43

Functions of LSRs

Component Function

Control plane Exchanges routing information

Exchanges labels

Data plane Forwards packets (LSRs and Edge LSRs)

Component Architecture of LSR


44/82

44

Component Architecture of LSR

This graphic shows the component architecture of an LSR. The primary function of an LSR is to forward labeled packets.

To accomplish this, every LSR needs a Layer 3 routing protocol and aprotocol to exchange labels.

LDP populates the LFIB table in the data plane that is used toforward labeled packets.


45/82

45

SIP Overview


46/82

46

SIP Overview

New generation of IP based services is now being quenchedby SIP the Session Initiation Protocol (RFP 3261)

SIP-based services: local and long distance telephony,

presence & Instant Messaging,

IP Centrex/Hosted PBX,

voice messaging,

push-to-talk, rich media conferencing, and more.

SIP utilizes its own unique user agents and servers, but it doesnot operate in a vacuum.

Comparable to the converging of the multimedia services itsupports, SIP works with a myriad of preexisting protocolsgoverning authentication, location, voice quality, etc.

A New Generation of Services


47/82

47


Flexible, extensible and open, SIP is galvanizing the power ofthe Internet and fixed and mobile IP networks to create a newgeneration of services.

Able to complete networked messages from multiple PCs andphones, SIP establishes sessions much like the Internet fromwhich it was modeled.

SIP operates independent of the underlying network transport

protocol and is indifferent to media. Defines how one or more participants end devices can create,

modify and terminate a connection whether the content is

voice, video, data orWeb-based.

SIP is analogous to HTTP in the way it constructs messages. Developers can more easily and quickly create applications using popular

programming languages such as J ava.



48/82

48


While some pundits predict that SIP will be to IP what SMTPand HTTP are to the Internet, others say it could signal the endof the AIN.

To date, the 3G Community has selected SIP as the sessioncontrol mechanism for the next generation cellular network.

Microsoft has chosen SIP for its real-time communicationsstrategy and has deployed it in Microsoft XP, Pocket PC and

MSN Messenger. MCI is using SIP to deploy advanced telephony services to its

IP communications customers. Presence will also enable users to instantly set up chat sessions and

audioconferences.

The SIP Advantage: Open, Extensible Web-Like


49/82

49

Communications

Like the Internet, SIP is easy to understand, extend and implement.

SIP extends the open-standards spirit of the Internet to messaging, enablingdisparate computers, phones, TVs and software to communicate.

SIP message is very similar to HTTP. Much of the syntax in message headers and many HTTP codes are

re-used.

For example, the error code for an address not found, 404,is identical to the Webs.

A SIP address, such as sip:[email protected], has the exact structure as an email

address. Using SIP, service providers can freely choose among standards-based

components and quickly harness new technologies.

Users can locate and contact one another regardless of media content and

numbers of participants. SIP negotiates sessions so that all participants can agree on and modify

session features.

It can even add, drop or transfer users.

SIP is not a cure-all


50/82

50

SIP is not a cure all

It is neither a session description protocol, nor does it provideconference control.

To describe the payload of message content andcharacteristics, SIP uses the Internets Session Description

Protocol (SDP) to describe the characteristics of the enddevices.

SIP also does not itself provide Quality of Service (QoS) and

interoperates with the Resource Reservation Setup Protocol(RSVP) for voice quality.

It also works with a number of other protocols, Lightweight Directory Access Protocol (LDAP) for location,

Remote Authentication Dial-In User Service (RADIUS) for authentication

RTP for real-time transmissions,

among many others.

SIP: basic requirements in communications


51/82

51

1. User location services2. Session establishment

3. Session participant management

4. Limited feature establishment An important feature of SIP is that it does not define the type

of session that is being established, only how it should bemanaged.

This flexibility means that SIP can be used for an enormousnumber of applications and services, including: interactive gaming,

music and video on demand voice, video and Web conferencing.

SIP features


52/82

52

SIP features

Below is are some of other SIP features that distinguish i t among newsignaling protocols

Messages are text based and hence are easy to read and debug. Programming new services is easier and more intuitive for designers.

Re-uses MIME type description in the same way that email clients do, soapplications associated with sessions can be launched automatically.

Re-uses several existing and mature internet services and protocols such asDNS, RTP, RSVP etc.

No new services have to be introduced to support the SIP infrastructure.Extensions are easily defined, enabling service providers to add them for newapplications without damaging their networks.

Older SIP-based equipment in the network will not impede newer SIP-based

services. For example, an older SIP implementation that does not support

method/ header utilized by a newer SIP application would simply ignore it.

SIP features


53/82

53

SIP features

Below is are some of other SIP features that dist inguish it

among new signaling protocols

Is transport layer independent. Therefore:

The underlying transport could be IP over ATM. SIP uses UDP as well as TCP protocol, flexiblyconnecting users

independent of the underlying infrastructure.

Supports multi-device feature levelling and negotiation. If a service or session initiates video and voice, voice can still be

transmitted to non-video enabled devices, or other device features can beused such as one way video streaming.

The Anatomy of a SIP Session


54/82

54


SIP sessions utilize up to four major components: SIP User Agents

SIP Registrar Servers

SIP Proxy Servers

SIP Redirect Servers.

Together, these systems deliver messages embedded with the SDP protocoldefining their content and characteristics to complete a SIP session.

SIP User Agents (UAs)

Are the end-user devices, such as cell phones, multimedia handsets, PCs,PDAs, etc. used to create and manage a SIP session.

The UA Client initiates the message. The UA Server responds to it.

SIP Registrar Servers

Are databases that contain the location of all UAs within a domain. In SIP messaging, these servers retrieve and send participants IP addresses

and other pertinent information to the SIP Proxy Server.



55/82

55

y

SIP Proxy Servers

Accept session requests made by a SIP UA and query the SIPRegistrar Server to obtain the recipient UAs addressing

information. It then forwards the session invitation directly to the recipient

UA if it is located in the same domain or to a Proxy Server if the

UA resides in another domain.SIP Redirect Servers

Allow SIP Proxy Servers to direct SIP session invitations toexternal domains.

SIP Redirect Servers may reside in the same hardware as SIPRegistrar Severs and SIP Proxy Servers.

Establishing A SIP Session Within the Same Domain


56/82

56

Establishing A SIP Session In Dissimilar Domains


57/82

57


58/82

58


59/82

59

VB Digital Video BroadcastingH.225 Covers narrow-band visual telephone servicesH.225 Annex GH.225EH.235 Security and authentication

H.323 SETH.245 Negotiates channel usage and capabilities

H.450Series defines Supplementary Services for H.323, call transfer, hold,park, message waiting, etc.

H.460

Optional extensions that might be implemented by an endpoint or a

Gatekeeper, including ITU-T Recommendations NAT/Firewall traversal.H.261 Video stream for transport using the real-time transportH.263 Bitstreamin the Real-time Transport ProtocolQ.931 manages call setup and terminationRAS Manages registration

RTCP RTP Control protocolRTP Real-Time TransportT.38 IP-based fax service mapsT.125 Multipoint Communication Service Protocol (MCS).

H.323 standard


60/82

60

The H.323 standard provides a foundation for audio, video, and datacommunications across IP-based networks, including the Internet.

H.323 is an umbrella recommendation from the ITU that sets standards formultimedia communications over LANs that do not provide a guaranteedQoS.

Therefore, the H.323 standards are important building blocks for a broadnew range of collaborative, LAN-based applications for multimediacommunications. It includes parts of :

H.225.0 - RAS, Q.931, H.245 RTP/RTCP and audio/video codecs, such as the audio codecs

(G.711, G.723.1, G.728, etc.) and video codecs (H.261, H.263) that compress anddecompress media streams.

Media streams are transported on RTP/RTCP.

RTP carries the actual media and

RTCP carries status and control information.

The signalling is transported reliably over TCP. It is a part of the ITU-T H.32x series of protocols, which also address

multimedia communications over ISDN, PSTN or SS7, and 3G Mobile.

Codecs


61/82

61

H.323 utilizes both ITU-defined codecs and codecs definedoutside the ITU.

Codecs that are widely implemented by H.323 equipmentincludes: Audio codecs: G.711 (64kbps per call), G.729 (including G.729a, 8kbps

per call), G.723.1, G.726

Text codecs: T.140

Video codecs: H.261, H.263, H.264

The main feature of codecs is the bandwidth that the can safemantaining a good quality of video, audio, etc..

H.323 Architecture


62/82

62

The H.323 system defines several network elements that worktogether in order to deliver rich multimedia communicationcapabilities.

Those elements are

Terminals

Multipoint Control Units (MCUs) Endpoints

Gateways

Gatekeepers Border Elements.

While not all elements are required, at least two terminals arerequired in order to enable communication between two

people. In most H.323 deployments, a gatekeeper is employed in order

to, among other things, facilitate address resolution.

Terminals


63/82

63

The most fundamental elements in any H.323 system. They might exist in the form of a simple IP phone, a powerfulhigh-definition videoconferencing system, or simply a PC

Inside an H.323 terminal is something referred to as a Protocolstack, which implements the functionality defined by the H.323system.

The protocol stack would include an implementation of the

basic protocol defined in ITU-T Recommendation H.225.0 andH.245, as well as RTP or other protocols described above.

The diagram, depicts a complete, sophisticated stack that

provides support for voice, video, and various forms of datacommunication. In reality, most H.323 systems do not implement such a wide array of

capabilities, but the logical arrangement is useful in understanding the

relationships.

Terminals


64/82

64

Multipoint Control Units


65/82

65

A MCU is responsible for managing multipoint conferences andis composed of two logical entities: Multipoint Controller (MC)

Multipoint Processor (MP).

In more practical terms, an MCU is a conference bridge notunlike the conference bridges used in the PSTN today.

The most significant difference, however, is that H.323 MCUs

might be capable of mixing or switching video, in addition to thenormal audio mixing done by a traditional conference bridge.

Some MCUs also provide multipoint data collaborationcapabilities. End user by placing a video call into an H.323 MCU might be able to see

all of the other participants in the conference, not only hear their voices.

Gateways


66/82

66

Enable communication between H.323 networks and othernetworks, such as PSTN or ISDN networks. If one party in a conversation is not an H.323 terminal, then the call must

pass through a gateway in order to enable both parties to communicate.

Gateways are widely used to: Enable the legacy PSTN phones to interconnect with the large,

international H.323 networks that are presently deployed by servicesproviders.

Used within the enterprise in order to enable enterprise IP phones tocommunicate through the service provider to users on the PSTN.

Enable videoconferencing devices based on H.320 and H.324 tocommunicate with H.323 systems.

Most of the third generation (3G) mobile networks deployed today utilize theH.324 protocol and are able to communicate withH.323-based terminals in corporate networks through such gateway devices.

Gatekeepers


67/82

67

Optional component in the H.323 network that providesservices to terminals, gateways, and MCU devices. Endpoint registration

Address resolution

Admission control User authentication, and so forth.

Address resolution is the most important task as it enables twoendpoints to contact each other without either endpoint havingto know the IP address of the other endpoint.

Gatekeepers may be designed to operate in one of twosignaling modes:

Direct routed mode Gatekeeper routed mode.

Gatekeepers


68/82

68

Direct routed mode.- Most efficient and most widely deployed. Endpoints utilize the RAS protocol in order to learn the IP address of the

remote endpoint and a call is established directly with the remote device.

Gatekeeper routed mode.- In this mode, call signaling always passes through the gatekeeper.

Requires more processing power

Gives the gatekeeper complete control over the call and the ability to

provide supplementary services on behalf of the endpoints.

H.323 endpoints use the RAS protocol to communicate with agatekeeper.

Likewise, gatekeepers use RAS to communicate with other gatekeepers.

A collection of endpoints that are registered to a singleGatekeeper in H.323 is referred to as a zone.

Border Elements and Peer Elements

B d El t d P El t ti l titi i il t


69/82

69

Border Elements and Peer Elements are optional entities similar toa Gatekeeper, but: Do not manage endpoints directly

Provide some services that are not described in the RAS protocol.

The role of a border or peer element is understood via the definition of an"administrative domain".

An administrative domain is the collection of all zones that areunder the control of a single organization, such as a serviceprovider.

The border element is a signaling entity that generally sits at theedge of the administrative domain and communicates with anotheradministrative domain.

Peer elements are entities with the administrative domain that,more or less, help to propagate information learned from the borderelements throughout the administrative domain.

Such architecture is intended to enable large-scale deployments.

Border Elements and Peer Elements


70/82

70


71/82

71

NGN: Next Generation Networking

NGN i b d t t d ib k hit t l l ti


72/82

72

NGN is a broad term to describe some key architectural evolutionsin telecommunication core and access networks that is beingdeployed and will revolution the networking over the next 5-10years.

The general idea behind NGN is that one network transports allinformation and services (voice, data, and all sorts of media suchas video) by encapsulating these into packets, like it is on theInternet.

NGNs are commonly built around the Internet Protocol, andtherefore the term "all-IP" is also sometimes used to describe thetransformation towards NGN.

Next Generation Networking ensures telecom services arealways accessible anywhere via any type of terminal.

NGN Characteristics

The following characteristics are fundamental to NGN:


73/82

73

The following characteristics are fundamental to NGN: Packet-based data transfer

Separate control functions for bearer capabilities, calls/sessions andapplications/services

De-coupling of service provision from the network, and provision of openinterfaces

Support for a wide range of service applications and mechanisms basedon service building blocks (including real-time/streaming/non-real-timeservices and multi-media)

Broadband capabilities with end-to-end QoS and transparency

Interworking with legacy networks via open interfaces

Generalized mobility

Unfettered access by users to different service providers

NGN Characteristics

The following characteristics are fundamental to NGN:


74/82

74

The following characteristics are fundamental to NGN: A variety of identification schemes that can be resolved to IP addresses

for the purposes of routing in IP networks

Unified service characteristics for the same service as perceived by theuser

Converged services between Fixed and Mobile networks

Independence of service-related functions from underlying transporttechnologies

Support of multiple last mile technologies Compliant with all Regulatory requirements (e.g. concerning emergency

communications and security/privacy, etc.)

Underlying Technology Components


75/82

75

NGN are based on Internet technologies including IP and MPLS. At the application level, SIP seems to be taking over from H.323.

Initially H.323 was the most popular protocol, though its popularitydecreased in the "local loop" due to its original poor traversal of

NAT and firewalls (now possible for H.323 devices to easily andconsistently traverse NAT and firewall).

For this reason as domestic VoIP services have been developed,SIP has been far more widely adopted.

However in voice networks where everything is under the control ofthe network operator or telco, many of the largest carriers useH.323 as the protocol of choice in their core backbones.

So really SIP is a useful tool for the "local loop" and H.323 is likethe "fiber backbone".

Underlying Technology Components

For voice applications one of the most important devices in NGN is a


76/82

76

For voice applications one of the most important devices in NGN is aSoftswitch - a programmable device that controls VoIP calls. It enables correct integration of different protocols within NGN.

The most important function of the Softswitch is creating the interface to theexisting telephone network, PSTN, through Signalling Gateways (SG) and Media

Gateways (MG).

One may quite often find the term Gatekeeper in NGN literature. This was originally a VoIP device, which converted (using gateways) voice and

data from their analog or digital switched-circuit form (PSTN, SS7) to the packet-

based one (IP). It controlled one or more gateways.

As soon as this kind of device started using the Media Gateway Control Protocol(and similars), the name was changed to Media Gateway Controller (MGC).

A Call Agent is a general name for devices/systems controlling calls. The IP Multimedia Subsystem (IMS) is a standardised NGN

architecture for an Internet media-services capability.

NGN Facts

Impacts of NGN


77/82

77

Impacts of NGN

NGN has numerous impacts on the telecom industry, not least ofwhich is the requirement to conform to NGN standards and tosupport

NGN-compatible technologies.Evolution of Networks to NGN

The ITU-T states: The evolution of networks to NGNs must allowfor the continuation of, and interoperability with, existing networks

while in parallel enabling the implementation of new capabilities. As NGN deployment is an evolutionary process, with numerous

networks being launched from various technological positions, it isnecessary to clearly identify stages of NGN compatibility or lack

thereof. In this regard, the NGN Enabled logo makes a great deal of sense.

NGN FactsQoS (Quality of Service)


78/82

78

Q (Q y )

There are no standard QoS criterion in the industry and it is best defined asa subjective measure of user satisfaction (e.g. speed, accuracy, reliability,and security).

This involves identification of parameters that can be directly observed and

measured where the service is accessed by users and network providers.

Flexibility within the global end-to-end NGN architecture is essential in orderto allow for each recognized operating agencys different regulatoryenvironment, service offerings, geographic span and network infrastructure.

These factors need to be taken into account when setting parameters for,and levels of, QoS in NGN.

Interoperability

NGN includes a wide range of protocols (including various profiles) at both

service and network levels.

Thus it is essential to ensure interoperability between different systems andnetworks. Interoperability is, in fact, a corner stone for the OSS industryregarding NGN.

NGN Facts

Security


79/82

79

y

Security is as crucial to the NGN as it is to current and legacynetwork environments.

Within the NGN, security issues interrelate to architecture, QoS,

network management, mobility, charging and payment.Generalized Mobility

NGN enables users and devices to access services irrespective ofchange of location or technical environment.

The degree of service availability may depend on several factors,including access network capabilities, service level agreementsbetween the users home networks and visited networks, etc.

It includes the ability to communicate from various locations using avariety of terminal equipment, with or without service continuity whilein transit or while changing access means.

NGN Facts

Service Capabilities and Architecture


80/82

80

p

NGN should provide and maintain a distinction betweenservices and the networks they run on, and ensure theservice architecture focuses on the interfaces to support

different business models and seamless communication indifferent environments.

Lastly, NGN must support critical legacy technologies (i.e.

PSTN) as they evolve to fully compatible NGN technologies.

NGN Facts


81/82

81

Mayor informacin


82/82

82

IMAGINAR

Centro de Investigacin para la Sociedad de

la InformacinP.O.Box: 17-04-10681

Quito-Ecuador

Telfono: 2400-937

Email: [email protected]

Site: www.imaginar.org

imaginar 7. p_protocolos_sobre ip

Documents