02ATM-Signaling and Addressing

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ATM - Signaling & Address - 129/09/200402:01:23 pm

ATM Signalingand Addressing


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Objectives


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In this module...


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Introduction

ATM connection services are implemented using permanent virtualconnections (PVCs) and switched virtual connections (SVCs).

PVC: the VPI/VCI values at each switching point in the connectionmust be manually configured. While this can be a tedious process, itonly needs to be done once.- PVCs are a good choice for connections that are always in use or arein frequent, high demand.

- Require labor-intensive configuration, they are not very scalable, andthey are not a good solution for infrequent or short-lived connections.

SVC: for on-demand connections. They are set up as needed and torndown when no longer needed. To achieve this dynamic behavior, SVCs

use signaling: End systems request connectivity to other end systems onan as needed basis.

Soft PVC: These connections are permanent but they are set upthrough signaling, they can ease configuration and can reroutethemselves if there is a failure in the link.


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Connection Setup and Signaling


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Connection Tear Down

1. Either the calling party or called party sends a releasemessage to the ATM network.

2. The ATM network returns a release complete message tothe called party.

3. The ATM network sends a release complete message to thecalling party.



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ATM Signaling ProtocolsUNI and NNI

ATM signaling protocols vary by the type of ATM networkinterface.

User-Network Interface (UNI) signalingused between anATM end-system and ATM switch across UNI links

UNI signaling can also be used between two ATM switches

Network-Network Interface (NNI) signalingused betweenATM switches across NNI links.



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Addressing

ATM addresses are needed for purposes of signaling whensetting up switched connections.

ATM addresses are also used by the Integrated Local

Management Protocol (ILMI, formerly Interim LocalManagement Protocol) to learn the addresses of neighboringswitches.


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ATM Address Formats

Public Address:- The ITU-T long ago settled on telephone number-like

addresses, called E.164 addresses or numbers, for use in publicATM (B-ISDN) networks.

Private Address:- The ATM Forum defined a private network addressing

scheme based on the semantics of an OSI Network Service AccessPoint (NSAP) address.

- This 20-byte private ATM address is called an ATM EndSystem Address (AESA), or ATM NSAP address (though it istechnically not a real NSAP address).

- It is specifically designed for use with private ATM networks


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Address Formats

An initial domain part (IDP)consists of two elements: an

authority and format identifier(AFI) that identifies the type andformat of the second element, theinitial domain identifier (IDI).

The IDI identifies the addressallocation and administrationauthority.

A domain specific part (DSP)contains the actual routinginformation in three elements: ahigh-order domain specific part(HO-DSP), an end systemidentifier (ESI), which is the MACaddress, and NSAP selector (SEL)field, used to identify LANemulation (LANE) components.


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Address Formats

Private ATM address formats are of three types that differ by thenature of their AFI and IDI :

DCC format (AFI=39)the IDI is a Data Country Code (DCC).DCC addresses are administered by the ISO national member body ineach country.

ICD format (AFI=47)the IDI is an International Code Designator

(ICD). ICD address codes identify particular internationalorganizations and are allocated by the British Standards Institute.

NSAP encoded E.164 format (AFI=45)the IDI is an E.164number.


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Address Formats

Sample ATM address,

47.00918100000000E04FACB401.00E04FACB401.00The AFI of 47 identifies this address as a ICD format address.


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Address Formats

There are two types of public E.164 addresses:

the NSAP encoded E.164 format

the E.164 native format, sometimes called an E.164 number


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Choosing an Address Format

The ATM Forum specifications through UNI 4.0 only specify thesethree valid types of AFI. Future specifications may allow more types.

The ATM Forum recommends that organizations or private networkservice providers use either the DCC or ICD formats to form their ownnumbering plan.

NSAP encoded E.164 format addresses are used for encoding E.164numbers within private networks that need to connect to publicnetworks that use native E.164 addresses.

Ob i i R i d ATM Add


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Obtaining Registered ATM Addresses

To satisfy the uniqueness requirement and facilitate distribution, anumber of registration authorities administer ATM addresses.

These addresses are usually distributed in sets of addresses having acommon prefix. The uniqueness of the prefix, which is used to define agroup of addresses, is ensured by the registration authority.

The recipient then allocates the remaining part of the ATM addressusing an addressing scheme that is appropriate for the private networkto create a set of unique addresses.

This allows private ATM networks to achieve global ATM

interconnection without the need to renumber addresses.

Obt i i R i t d ATM Add


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Obtaining Registered ATM Addresses

AESA prefixes are differentiated by ownership, as follows:

Customer-owned ATM prefixa prefix allocated directly to aprivate network by a national or world registration authority.

Service provider ATM prefixa prefix allocated to a serviceprovider by a national or world registration authority. An ATM service

provider might suballocate part of its address space to its customers. Unregistered ATM prefixa prefix, or an extension of such a prefix,that is not obtained from a national or world registration authority.Private ATM networks can use unregistered prefixes to deriveunregistered addresses, but these addresses are only used within that

private network because they are not guaranteed to be globally unique.

Cl d U G Si li


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Closed User Group Signaling

Closed user groups (CUGs) function as ATM virtual privatenetworks (VPNs).

Multiple CUGs can be defined, and a specific user can be a memberof one or more CUGs.

Members of a CUG can communicate among themselves, but notwith users outside the group.

Specific users can have additional restrictions that prevent them fromoriginating or receiving calls from other members of the CUG.

Additional restrictions on originating and receiving calls to or frommembers of other CUGs can be configured.

M lti i t t P i t F l Si li


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Multipoint-to-Point Funnel Signaling

Multipoint-to-point funnel signaling (funneling) merges multiple

incoming SVCs into a single outgoing SVC.An incoming SVC is called a leaf SVC,

and the outgoing SVC is called the funnel SVC.

Example: Multiple video transmitting sources converge on a singlevirtual connection such that it looks like a point-to-point connection.


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That's all, folks!!hat's all, folks!!...till we meet again......till we meet again...

02ATM-Signaling and Addressing

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