ACHIEVING MULTIMEDIA QOS OVER HYBRID IP/PSTN INFRASTRUCTURES QOS Signalling and Media Gateway Control ITU-T SG13/SG16 Workshop on IP Networking and Mediacom

ACHIEVING MULTIMEDIA QOS OVER HYBRID IP/PSTN INFRASTRUCTURES QOS Signalling and Media Gateway ControlITU-T SG13/SG16 Workshop on IP Networking and Mediacom 2004

Tom Taylor -- [email protected]

PTT: 26 Apr 2001 ITU-T SG13/SG16 Workshop on IP Networking and Mediacom 2004, - 2

Contents

• RSVP as the bandwidth reservation signalling protocol– New RSVP policy objects to help

• MGC and MG at the IP-PSTN boundary– Media gateway control– Separate paths for signalling and media

• Fitting RSVP into the media gateway control picture

• Supplementary Material – Detailed operation of RSVP signalling


Why RSVP?

• The need: ensure network expedites real-time media flows

• The network can't do it alone– the output from many real-time apps is

difficult to identify

• The network needs help from the application– signalled QoS is a requirement

• RSVP works with all applications and signaling protocols– e.g., SIP, H.323


Reservation Parameters

• User Authentication (AUTH_USER)

• Application Identification (AUTH_APP) Solves application flow classification issues

• DCLASS (DSCP)

• TCLASS (802.1p)

• SENDER_TSPEC / FLOW_SPEC– Token Bucket Rate, Token Bucket Size, Peak Data

Rate

• SENDER_TEMPLATE / FILTER_SPEC– Source IP Address and Port number

• SESSION– Destination IP Address and Port number


Where is RSVP implemented?

• IP Phones, SoftPhones, IPT Gateways (Hosts)– Host signals network for desired QoS– Implement simple Host RSVP with Policy extensions

• Policy Enforcement Point (PEP) Routers– Edge routers maintain BW reservations for microflows– Core routers use DiffServ or TE’d paths– Implement COPS-for-RSVP client

• Policy Decision Point (PDP) Policy Server – Provides Policy Decisions to Network Elements and Hosts– Implement COPS-for-RSVP server


Architectural View

DiffServ Domain

DS InteriorNodesIngress

PEP

PolicyServer(PDP)

EgressPEP

Host 2Host 1

Access Network

Access Network


The Decomposed Gateway Model

PSTNIP Network

MediaGateway

Controller

Host

MediaGateway

Gatekeeper,Proxy, etc.Call

Signalling

MediaFlows

GatewayControl


Media Gateway Control and RSVP• Media Gateway Controller both have to be

involved in RSVP signalling– MGC has to handle authorization, billing– MGC knows other information (e.g. application

class, destination address) – but RSVP messaging has to follow path of media

flow -- most easily done if sent by MG

• Implies requirement for Megaco/H.248 package to pass necessary information from MGC to MG

Only need QOS awareness at ingress and egress pointsNo need for any intermediate call signalling entity to get involved

Supplementary Material Detailed operation of RSVP signalling

These slides were taken from a presentation by Ralph These slides were taken from a presentation by Ralph Santitoro, Director of QoS Architecture, NortelSantitoro, Director of QoS Architecture, Nortel


RSVP Signaling Architectural Overview• Hosts initiate and respond to RSVP messages

– Reservation initiation, failure, termination or network policy change

• Edge Routers Police BW and Policy Reservations– DS Edge Routers maintain RSVP soft-state– DS Core Routers do not maintain RSVP soft-state

• Use DiffServ or TE’d paths to provide QoS assurances in the core

• Admission Control decided by Policy Server (PDP) or Router LDP

• RSVP messages flow end-to-end

• RSVP Reservations must be made separately in each directions

• RSVP-enabled hosts benefit– Non-RSVP-aware hosts either:

• Achieve no QoS• Use other access technology-specific QoS• Use proprietary mechanisms


RSVP Reservation- DS Edge Node DiffServ Domain


PEP

PolicyServer(PDP)

EgressPEP

2. COPS-RSVP

2. Path Message encapsulated in COPS-RSVP message. PDP instructs ingress PEP to forward Path Msg. and keep soft-state for reservation

3. P-HOP

3. Ingress PEP adds egress interface to P-HOP (Route pinning). Router Alert Option disabled.

4. DS Interior Nodes forward Path Message

4. Path

5. Egress PEP processes Path Msg. and enables Router Alert Option

5. Process Path Msg.

If no BW is available for reservation, PEP initiates Path failure

1. Path

1. Host 1 initiates Path Msg.

Host 2Host 1

Access Network

Access Network


RSVP Reservation- DS Edge Node (cont.) DiffServ Domain


PEP

PolicyServer(PDP)

EgressPEP

8. COPS-PR

8. If reservation succeeds, PDP sends new filters down to PEP

9. COPS-RSVP

9. Resv message sent by Ingress PEP to PDP to confirm reservation. PDP can return DCLASS object to be sent in Resv msg. sent to Host 1.

7. COPS-RSVP

7. If no BW available, PDP informs Egress PEP to generate ResvErr to Host 1. If reservation accepted, Egress PEP forwards Resv to Host 1.

Path

6. Resv

6. Host 2 generates Resv Msg.

Host 1 Host 2

Access Network

Access Network


RSVP Reservation - DS Edge Node (cont.) DiffServ Domain


PEP

PolicyServer(PDP)

EgressPEP

10. COPS-PR

10. PDP sends new filters down to PEP.

11. Resv

11. Ingress PEP accepts reservation by sending RESV message to Host 1. If PDP rejected reservation, PEP sends ResvErr back to interface specified inside RSVP N-HOP object.

Path

Host 1 Host 2

Access Network

Access Network


DS Domain 1

DS InteriorNode

IngressEdgePEP

EgressEdgePEP

DS Domain 2

BoundaryPEP

PolicyServer(PDP)

DS InteriorNode

Path

4a. COPS-RSVP

4a. Path Msg. encapsulated in COPS-RSVP message. PDP instructs boundary PEP to forward Path Msg. and keep soft-state for reservation

RSVP Reservation- DS Boundary Node• The following steps are introduced into the reservation if there are

RSVP-capable Boundary Nodes interconnecting DS Domains

If no BW is available for reservation, PEP initiates Path failure

4c. DS Interior Nodes forward Path Message

4c. Path

4b. Boundary PEP adds its egress interface to RSVP P-HOP object

4b. New P-HOP

Host 1 Host 2Access Network Access

Network


DS Domain 1

DS InteriorNode

IngressEdgePEP

EgressEdgePEP

DS Domain 2

BoundaryPEP

PolicyServer(PDP)

DS InteriorNode

Path

Resv

RSVP Reservation- DS Boundary Node (cont.)

8a. If no BW available, PDP informs boundary PEP to generate ResvErr to Host 1. If reservation accepted, Egress PEP forwards Resv to Host 1.

8a. COPS-RSVP

Path

8b. COPS-PR

8b. If reservation succeeds, PDP sends new filters down to PEP

8c. Resv

8c. Boundary PEP admits reservation by sending RESV message to Host 1. If PDP rejected reservation, PEP sends ResvErr back to interface specified in RSVP N-HOP object.

Host 1 Host 2Access Network Access

Network


References• “Resource ReSerVation Protocol (RSVP), RFC 2205

• “Identity Representation for RSVP”, RFC 2752

• “RSVP Extensions for Policy Control”, RFC 2750

• “COPS usage for RSVP”, RFC 2749

• “Application and Sub Application Identity Policy Element for Use with RSVP”, RFC 2872

• “Format for RSVP DCLASS Object”, RFC 2996

• “Standardized Application Identifiers for RSVP Identity Policy Element”, draft-santitoro-rap-policy-appids-01.txt

• “New RSVP ErrorValues to Modify Sender Behavior”, draft-santitoro-rap-policy-errorcodes-01.txt

• “Session Authorization for RSVP”, draft-hkg-rap-rsvp-authsession-00.txt

• “Session setup with media authorization”, draft-hamer-sip-session-auth-00.txt

Documents

ACHIEVING MULTIMEDIA QOS OVER HYBRID IP/PSTN INFRASTRUCTURES QOS Signalling and Media Gateway Control ITU-T SG13/SG16 Workshop on IP Networking and Mediacom