Atm network interworking

ATM – MPLS Network Interworking

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Topics
Introduction to ATM–MPLS Interworking Encapsulation Formats Interworking Procedures OtherTechnical Issues Future Work Summary

Topics
Introduction to ATM–MPLS Interworking Encapsulation Formats Interworking Procedures Other Technical Issues Future Work Summary

Motivation
Many telecom carriers use ATM technology today to deliver revenue-generating services (e.g. voice, leased line, frame relay, native ATM) at the network edge. Many assume that it will be cheaper in the future tobuild and manage MPLS core networks, as opposed to ATM. The particular technologies used within a carrier’s network (e.g. ATM, MPLS, optical) must be transparent to the customer.

ATM–MPLS–ATM Reference Diagram (Network Interworking)
INE INE

ATM Network

MPLS Network

ATM Network

ATM Service

ATM Service

Voice, Video, Data Apps

Voice, Video, Data Apps

“INE” = InterworkingNetwork Element

MPLS–ATM-MPLS Reference Diagram (Network Interworking)
INE INE

MPLS Network
Services over MPLS

ATM Network

MPLS Network
Services over MPLS Voice, Video, Data Apps

Voice, Video, Data Apps

“INE” = Interworking Network Element

ATM–MPLS Reference Diagram (Service Interworking)
INE

ATM Network
Services over ATM

MPLS Network
Services over MPLS Voice,Video, Data Apps

Voice, Video, Data Apps

“INE” = Interworking Network Element

ATM Forum Specifications
The ATM Forum is specifying methods for ATM-MPLS interworking: – Addresses future co-existence of ATM & MPLS technologies within networks. – First fruits: AF-AIC-0178.000 (ftp://ftp.atmforum.com/pub/approvedspecs/af-aic-0178.000.pdf) – Ambitious follow-on plan

Requirements
Initial ATMForum specification focuses on user plane aspects of ATM-MPLS-ATM network interworking: – Multiple ATM VCCs and/or VPCs within a MPLS LSP, – Support ATM traffic contracts and QoS, – Transport all AAL types, – Transport OAM and RM cells, – Transport single or multiple ATM cells within a single MPLS frame, and – Provide transparency to ATM cells.

ATM Cells to/from MPLS Frames
ATM Network
INELSP

MPLS Network
INE

ATM Network

= user cells from VC #1 = user cells from VC #2 = user cells from VC #3 = OAM cells

Topics
Introduction to ATM–MPLS Interworking Encapsulation Formats Interworking Procedures Other Technical Issues Future Work Summary

ATM Cell Format
Fixed-length cells are used to transport data, voice, and video inside ATM networks.
8 7 6 5 4 3 2 1 1 2 3GFC VPI VCI VCI HEC ATM cell payload (48 octets) PTI

VPI VCI

CLP

4 5

6 - 53

AAL-5 PDU Frame Format
Variable-length AAL-5 frames are segmented into cells for transport across ATM networks.
8 7 6 5 4 3 2 1

Payload (1 – 65,535 octets) Pad (0 - 47 octets) UU (1 octet) CPI (1 octet) Length (2 octets) CRC (4 octets)

MPLS Frame Format
Variable-length frames are used to transportdata, voice, and video inside MPLS networks.
Label (20 bits) Label (20 bits) Exp (3 bits) Exp (3 bits) Stack (1 bit) Stack (1 bit) TTL (8 bits) TTL (8 bits)

Payload

ATM-MPLS-ATM Encapsulation Modes
Single Cell Mode - mandatory
–

Each MPLS frame contains a single ATM cell More efficient than single cell mode Most efficient of all modes No support for AAL types 1, 2, 3, and 4 Loss of...