P_protocolos_sobre%20IP.pdf

8/17/2019 P_protocolos_sobre%20IP.pdf

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Protocolos sobre IP

Fausto Vasco


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Objetivos

• Queremos hacer una descripción rápida de los protocolosde comunicaciones que más influencian el mercado

actual:

– Frame Relay

– X.25

– MPLS

– SIP

– H323 – NGN


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X.25

• X.25 is an ITU-T standard data l ink layer pro toco l for packetswi tched WAN communication.

• An X.25 WAN consists of packet-switching exchange (PSE ) nodes as

the networking hardware, and leased l ines , POTS connections or

ISDN connections as physical links .

• X.25 is part of the OSI pro toco l sui te , a family of protocols that was

used especially during the 1980s .

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


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Addressing and virtual circuits

• X.25 supports two types of vir tual circui ts : – Switched Vir tual Circui ts (SVC ) which are established as and when required

through a cal l establ ishm ent and clear ing pro cedure

– Permanent Virtual Circu its (PVC ) which are preconf igured into the network.

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

– three-digi t Data Country Code (DCC ) plus a network dig i t , together forming the

four-dig i t Data Network Identification Code (DNIC ),

– followed by the National Terminal Number (NTN ) of at most ten digi ts .

• Note the use of a single netwo rk dig i t , seemingly allowing for only

10 netwo rk carr iers per coun try , but some countries are assigned

more than one DCC to avoid this limitation.

• One DTE-DCE inter face to an X.25 network has a maximum o f

4095 log ical channels on which it is allowed to establish virtual

cal ls and permanent vir tual circui ts .


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Architecture

• The general concept o f X.25 was to create a universal andglobal packet-sw i tched netwo rk.

• Much of the X.25 sys tem is a description of the r igorous error

correct ion needed to achieve this, as well as more eff icientshar ing of capital-intensive phys ical resources .

• The X.25 specification defines only the interface between a

subscr iber (DTE) and an X.25 network (DCE).

• Replaced by Frame Relay is now considered an obsolete

pro toco l .

• X.25 was the base to new pro toco ls like Frame Relay and

ATM which use extensively the Virtual Circu i ts .


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An Efficient and Flexible WAN Technology

• Frame Relay has become the most w idely used WAN techno logy . – primarily because of its pr ice and f lexibi l i ty .

• Frame Relay reduces netwo rk costs by using less equipm ent , less

complexi ty , and an easier implementat ion .

• With increasing globalization and the grow th of one-to-many

branch of f ice topo logies , Frame Relay offers simpler network

architecture and lower cost of ownership.


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The Frame Relay WAN

• Frame Relay has low er overhead than X.25 because it hasfewer capabilities.

– Frame Relay does not provide error correct ion .

• This is left to higher layers.

– The Frame Relay node simp ly drops packets without notification when

it detects errors .


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The Frame Relay WAN

• Frame Relay handles vo lume and speed eff ic ient ly bycombining the necessary funct ions o f the L2 and L3 into one

simple protocol.

• As a data l ink proto co l , Frame Relay provides: – Access to a network,

– Delimits and del ivers frames in proper order, and

– Recognizes transmission errors through a standard CRC .

• As a network pro toco l , Frame Relay provides: – Mult ip le logical connect ions over a single physical circuit and

– Allows the network to rou te data over those connections.

• Frame Relay operates between an end -user device , such asa LAN bridge or router , and a netwo rk .

– Some networks use Frame Relay itself , but others use digi ta l ci rcui t

swi tch ing or ATM cel l relay systems.


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Virtual Circuits

• The connect ion through a Frame Relay network between twoDTEs is called a vi r tual ci rcui t (VC ).

– There is no direct electr ical connect ion from end to end.

– The connection is logical .

– With VCs , Frame Relay shares the bandwidth among mult ip le users

and any single si te can communica te with any other single si te

w i thout using mult ip le dedicated physical l ines .

• There are two ways to establish VCs: – SVC

– PVC


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Local Significance

• VCs provide a bid i rect ional communication path from onedevice to another.

• VCs are ident i f ied by DLCIs .

– Typically are ass igned by the service provider . – Local signi f icance , which means that the values themselves are not

unique in the Frame Relay WAN .

– Two devices connected by a VC may use a dif ferent DLCI value to

refer to the same connect ion .


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Local Significance


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Multiple VCs

• Frame Relay is stat ist ical ly mult ip lexed , meaning that itt ransm its on ly one frame at a t ime , but that many logical

connect ions can co-exist on a sing le phys ical line .

• The rou ter connected to the Frame Relay network may havemult ip le VCs connecting it to various endpoints .

– Mult iple VCs on a single physical line are dist inguished because each

VC has its own DLCI .

– Very cost-effect ive – Each endpoint needs only a single access l ine and interface .

– Average bandw idth requirement of the VCs, rather than on the

maximum bandwid th requirement.


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The Frame Relay Encapsulation Process

• Frame Relay is a Layer 2 pro toco l . – Frame Relay accepts a packet f rom a network layer protocol such as

IP.

• It then wraps it with an address f ield that contains the DLCI and a

checksum .


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Frame Relay Topologies

• When more than two si tes are to be connected, you mustconsider the topo logy of the connections between them.

• Every network or network segment can be viewed as being one

of three topo logy types : – Star (hub and spoke) – fu l l mesh , or

– part ial mesh .


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Frame Relay Address Mapping

• Before a router is able to t ransmit data over Frame Relay, itneeds to know which local DLCI maps to the Layer 3

address of the remo te dest inat ion .

• This address-to-DLCI mapping can be accompl ished eitherby:

– stat ic mapping

• By entering a static map

– dynamic mapping .• Inv erse ARP.- The Frame Relay rou ter sends out Inverse ARP requests on

its PVC to d iscover the L3 address of the remote device.


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Local Management Interface (LMI)

• The Frame Relay or ig inal design provides packet -sw i tched datatransfer with min imum end-to-end delays .

• The original design om i ts anyth ing that might contr ibu te to delay .

• When vendors implemented Frame Relay as a separate

technology rather than as one component of ISDN, they decided that

there was a need for DTEs to dynam ical ly acquire informat ion

about the status of the network.

– The orig inal design did not inc lude this feature.

– A consor t ium of Cisco, DEC, Northern Telecom, and StrataCom extended the

Frame Relay pro toco l to provide addit ional capabi l i t ies for complex

internetworking environments.

– These extensions are referred to collectively as the LMI .

• Basically, the LMI is a keepal ive mechan ism that provides status informat ion about Frame Relay connec tions between the router

(DTE ) and the Frame Relay sw itch (DCE ).


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Local Management Interface (LMI)


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LMI Extensions

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

• Informs PVC integri ty by communicating and synchron izing between

devices , periodically repo rt ing new PVCs and the delet ion of PVCs .

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

• Multicasting supports the eff ic ient del ivery o f rout ing proto col messages

and address resolut ion p rocedures that are typically sent to many

dest inat ions simul taneously .Global addressing

• Gives connection ident i f iers glo bal rather than local signi f icance

• This makes the Frame Relay network resemb le a LAN in terms of

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

Simple flow control

• Provides for an XON/XOFF f low contro l mechanism that applies to the

entire Frame Relay interface.


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LMI

• The three possib le PVC states are as follows: – Active state – Indicates that the connect ion is act ive and that routers

can exchange data.

– Inactive state – Indicates that the local connect ion to the Frame Relayswitch is work ing , but the remote rou ter connection to the Frame Relayswitch is not wo rk ing .

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

Frame Relay switch.


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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 po rt speed .

Access rate is the rate at which your access ci rcu i ts join theFrame Relay network .

– Port speeds are clocked on the Frame Relay sw itch .

– It is not possib le to send data at higher than po rt speed .

Committed Information Rate (CIR)

• Customers nego tiate CIRs with service providers for each

PVC .

• The service pro vider guarantees that the customer can senddata at the CIR .

• All frames received at or below the CIR are accepted.


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Frame Relay Key Terminology

• A great advantage of Frame Relay is that any netwo rk capaci ty that isbeing unused is made available or shared with al l customers , usually at

no extra charge .

• This al lows custom ers to "burs t " over their CIR as a bonus.

Oversubscription

• Service prov iders sel l more capaci ty than they have on the assumption

that not everyone wi l l demand their entitled capacity al l of the time .

• Because of oversubscr ip t ion , there will be instances when the sum of CIRs

from mult iple PVCs to a given location is higher than the port or access

channel rate . – This can cause t raff ic issues , such as congest ion and dropp ed traf f ic .


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Paying for Frame Relay: Bursting

• Frame Relay can allow custom ers to dynamically access this extrabandwidth and "burs t " over their CIR for free .

• Various terms are used to descr ibe bu rst rates including the Committed

Burst Information Rate (CBIR ) and Excess Burst Size (BE ).

CBIR• Is a negot iated rate abo ve the CIR which the customer can use to transmit

for shor t burs t . It allows traffic to burs t to higher speeds , as available

network bandwidth permits.

– However, it cannot exceed the po rt speed of the link. – The durat ion of a burs t transmission is the Comm it ted Time .

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

BE

• The BE is the term used to desc ribe the bandw idth avai lable above theCBIR up to the access rate of the link . – BE , is no t negotiated .

– Frames may be transmit ted at this level but wi l l most l ike ly be dropped .


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Paying for Frame Relay: Bursting


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Frame Relay Flow Control

• Frame Relay reduces network overhead by implementingsimple

congest ion-not i f icat ion mechanisms.

– Forward Explicit Congestion Notification (FECN )

– Backward Explicit Congestion Notification (BECN ).

– Discard El igib i l i ty (DE ) bit, which identifies less important traff ic that

can be dropped during congest ion periods.


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Objectives

• Describe Multiprotocol Label Switching (MPLS) features andoperat ion .

• Identi fy the f ields and format of an MPLS label .

• Describe the purpose of the cont ro l and data p lanes in theMPLS architecture.

• Describe the funct ion and archi tecture of Label Switch

Routers (LSRs ) and Edge LSRs .


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WAN Topologies

• With MPLS, a si te requ ires only one connect ion to theMPLS SP .

– High-performance method for forwarding packets through a network.

– Enables rou ters at the edge o f a network to apply simple labels in the

form of numbers to these packets.

– Routers can then swi tch packets according to labels , incurring minimal

overhead for rout ing lookup .


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Basic Mult iprotocol Label Switching (MPLS) Features

• MPLS reduces rou ting lookups .• MPLS fo rwards packets based on labels .

• Labels usually correspond to IP dest inat ion network s (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 suppor ts forwarding of all Layer 3 pro tocols , not justIP.


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MPLS Operation

• Only edge routers must perform a rout ing lookup .• Core rou ters sw itch packets based on simple label lookups

and swap labels .


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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)


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Standard IP Switching Overview

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CEF Switching Overview

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MPLS Switching Overview

Edge LSR

MPLSIP

R1

Edge LSR

R3 LSR R2 LSR

R6

Edge LSR

Station A Station B

IP Domain

L

LabelInstructions

Internal Table

LSR

MPLSMPLS

R4 LSR R5 LSR


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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 2

and Layer 3 headers (frame mode MPLS).

• MPLS over ATM uses the ATM header as the label (cell mode

MPLS).


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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 of

service (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 this

label 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


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Label Stack

• PID in a Layer 2 header specifies that the payload starts with a

label (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.


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Frame Mode MPLS Operation

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


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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


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Control Plane Components Example

• Information from control plane is sent to the data plane.

Label Switch Routers (LSRs)


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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


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Functions of LSRs

Component Function

Control plane – Exchanges routing information

– Exchanges labels

Data plane – Forwards packets (LSRs and Edge LSRs)

Component Architecture of LSR


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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 a

protocol to exchange labels.

• LDP populates the LFIB table in the data plane that is used to

forward labeled packets.


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SIP Overview


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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 does

not operate in a vacuum.

• Comparable to the converging of the multimedia services it

supports, SIP works with a myriad of preexisting protocols

governing authentication, location, voice quality, etc.

A New Generation of Services


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• Flexible, extensible and open, SIP is galvanizing the power ofthe Internet and fixed and mobile IP networks to create a new

generation of services.

• Able to complete networked messages from multiple PCs and

phones, SIP establishes sessions much like the Internet from

which it was modeled.

• SIP operates independent of the underlying network transport

protocol and is indifferent to media.• Defines how one or more participant’s 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 Java.



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

of the AIN.

• To date, the 3G Community has selected SIP as the session

control mechanism for the next generation cellular network.

• Microsoft has chosen SIP for its real-time communications

strategy 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


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Communications

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

• SIP extends the open-standards spirit of the Internet to messaging, enabling

disparate 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 Web’s.

– 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


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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 and

characteristics, SIP uses the Internet’s 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


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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 be

managed.

• This flexibility means that SIP can be used for an enormous

number of applications and services, including:

– interactive gaming,

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

SIP features


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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 as

DNS, 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 new

applications 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


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SIP features

Below is are some of other SIP features that dist inguish itamong new signaling protocols

•Is transport layer independent. Therefore:

– The underlying transport could be IP over ATM. – SIP uses UDP as well as TCP protocol, flexibly connecting 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 be

used such as one way video streaming.

The Anatomy of a SIP Session


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• 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 protocol

defining 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 Regist rar 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.



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y

SIP Proxy Servers

• Accept session requests made by a SIP UA and query the SIP

Registrar Server to obtain the recipient UA’s 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 Red irect Servers

• Allow SIP Proxy Servers to direct SIP session invitations to

external domains.

• SIP Redirect Servers may reside in the same hardware as SIP

Registrar Severs and SIP Proxy Servers.

Establishing A SIP Session Within the Same Domain


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Establishing A SIP Session In Dissimilar Domains


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VB Digital Video BroadcastingH.225 Covers narrow-band visual telephone services

H.225 Annex G

H.225E

H.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 transport

H.263 Bitstream in the Real-time Transport Protocol

Q.931 manages call setup and termination

RAS Manages registration

RTCP RTP Control protocolRTP Real-Time Transport

T.38 IP-based fax service maps

T.125 Multipoint Communication Service Protocol (MCS).

H.323 standard


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• 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 for

multimedia communications over LANs that do not provide a guaranteed

QoS.

• Therefore, the H.323 standards are important building blocks for a broad

new range of collaborative, LAN-based applications for multimedia

communications. 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


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

• Codecs that are widely implemented by H.323 equipment

includes:

– 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 safe

mantaining a good quality of video, audio, etc..

H.323 Architecture


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

capabilities.

• Those elements are

– Terminals

– Multipoint Control Units (MCUs) Endpoints

– Gateways

– Gatekeepers – Border Elements.

• While not all elements are required, at least two terminals are

required 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


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• The most fundamental elements in any H.323 system.• They might exist in the form of a simple IP phone, a powerful

high-definition videoconferencing system, or simply a PC

• Inside an H.323 terminal is something referred to as a Protocol

stack, which implements the functionality defined by the H.323

system.

• 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


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Multipoint Control Units


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• 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 collaboration

capabilities.

– 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


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• 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 services

providers.

– 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 to

communicate with H.323 systems.

• Most of the third generation (3G) mobile networks deployed today utilize theH.324 protocol and are able to communicate with

H.323-based terminals in corporate networks through such gateway devices.

Gatekeepers


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• 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 two

endpoints to contact each other without either endpoint having

to know the IP address of the other endpoint.

• Gatekeepers may be designed to operate in one of two

signaling modes:

– Direct routed mode

– Gatekeeper routed mode.

Gatekeepers


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• 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 a

gatekeeper.

– Likewise, gatekeepers use RAS to communicate with other gatekeepers.

• A collection of endpoints that are registered to a single

Gatekeeper 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


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• Border Elements and Peer Elements are optional entities similar to

a 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 are

under the control of a single organization, such as a service

provider.

• The border element is a signaling entity that generally sits at the

edge of the administrative domain and communicates with another

administrative domain.

• Peer elements are entities with the administrative domain that,more or less, help to propagate information learned from the border

elements throughout the administrative domain.

• Such architecture is intended to enable large-scale deployments.

Border Elements and Peer Elements


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NGN: Next Generation Networking

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


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• NGN is a broad term to describe some key architectural evolutions

in telecommunication core and access networks that is being

deployed and will revolution the networking over the next 5-10

years.

• The general idea behind NGN is that one network transports allinformation and services (voice, data, and all sorts of media such

as video) by encapsulating these into packets, like it is on the

Internet.

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

transformation towards NGN.

• Next Generation Networking ensures telecom services are

always accessible — anywhere — via any type of terminal.

NGN Characteristics

• The following characteristics are fundamental to NGN:


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– Packet-based data transfer

– Separate control functions for bearer capabilities, calls/sessions and

applications/services

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

– Support for a wide range of service applications and mechanisms based

on service building blocks (including real-time/streaming/non-real-time

services 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



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– 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 the

user

– Converged services between Fixed and Mobile networks

– Independence of service-related functions from underlying transport

technologies

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

communications and security/privacy, etc.)

Underlying Technology Components


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• 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 popularity

decreased 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 of

the network operator or telco, many of the largest carriers use

H.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


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

Softswitch - 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 the

existing 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 o f NGN


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Impacts o f NGN

• NGN has numerous impacts on the telecom industry, not least of

which is the requirement to conform to NGN standards and to

support

NGN-compatible technologies.Evolut ion o f Netwo rks to NGN

• The ITU-T states: “The evolution of networks to NGNs must allow

for 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 is

necessary 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 (Quali ty of Service)


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( y )

• There are no standard QoS criterion in the industry and it is best defined as

a ‘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 order

to allow for each recognized operating agency’s different regulatory

environment, 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.

Interoperabil i ty

• 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 and

networks. Interoperability is, in fact, a corner stone for the OSS industry

regarding NGN.

NGN Facts

Secur i ty


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y

• Security is as crucial to the NGN as it is to current and legacy

network environments.

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

network management, mobility, charging and payment.General ized Mobil i ty

• NGN enables users and devices to access services irrespective of

change of location or technical environment.

• The degree of service availability may depend on several factors,

including access network capabilities, service level agreements

between 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 while

in transit or while changing access means.

NGN Facts

Service Capabi l i t ies and Arch i tectu re


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p

• NGN should provide and maintain a distinction between

services and the networks they run on, and ensure the

service 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


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Mayor información


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IMAGINAR

Centro de Investigación para la Sociedad de

la InformaciónP.O.Box: 17-04-10681

Quito-Ecuador

Teléfono: 2400-937

Email: [email protected]

Site: www.imaginar.org

Documents

P_protocolos_sobre%20IP.pdf