QoS control by means of COPS to Support SIP-based applications S. Salsano, L. Veltri IEEE Networks, March/April 2002 R93944010賈　立 R93922011黃文彬 R93922053陳育成 R93922095陳奕安

Contents Introduction The COPS role for Dynamic DiffServ resource allocation Definition of the COPS Interfaces IP Telephony : A COPS Based QoS model Implementation Testbed conclusion 11/22/2018

What is QoS What is quality of service? What does it take for the Internet to support QoS? Existing Internet QoS architectures: Integrated services, differentiated services, and MPLS overview. 11/22/2018

What is QoS User point of view: Relaxed definition: Assurance of end-to-end service. E.g. Guaranteed delay (VoIP), Guaranteed bandwidth (VPN) Relaxed definition: Service differentiation: different packets is treated differently. end-to-end service guarantees may be achieved by provisioning. e.g. only a small portion of high priority packets. Existing IP networks only support best effort service. Adding service differentiation is non-trivial. 11/22/2018

What is QoS(Cont.) Applications that need QoS Common QoS parameters: VoIP: bounded delay VPN: bounded bandwidth Video conferencing: bounded delay and bounded loss rate Common QoS parameters: delay/delay variation (jitter) Bandwidth error rate 11/22/2018

What is QoS(Cont.) Per flow QoS guarantees and aggregate QoS guarantees Statistical QoS guarantees .vs. deterministic QoS guarantees 11/22/2018

What is needed to support QoS Between the network and its clients: Traffic contract. Traffic specification/desired QoS/supported QoS At network edge: Signaling and admission control Packet classification/marking Traffic shaping Packet classification/marking and traffic shaping is also called traffic conditioning. Traffic policing 11/22/2018

What is needed to support QoS At routers: classification and scheduling: FCFS won't work, need more advanced packet scheduling scheme (Fair Queuing) Routing algorithm need to improve: find a path that satisfies QoS constraints (QoS/policy/constraint based routing). Buffer management. Traffic monitoring: find problems as early as possible Traffic reshaping (at merge and fork points) 11/22/2018

QoS in the Internet: Do we really need it? Alternative: buy excessive bandwidth Everything is simple in the Internet without QoS, everything seems to be much harder in the Internet with QoS support. What is the main problem? Complexity and scalability of QoS mechanisms Which is cheaper: higher network speed or network with QoS support. Where is the balance? A guess: Some form of QoS support will be there, per flow QoS guarantee may or may not ever be deployed. 11/22/2018

Intergrated Services (IntServ) Trying to match the user demand by providing per flow QoS guarantees. Signaling protocol: RSVP IntServ is a reservation based approach Main problem: Router complexity (scalability) 11/22/2018

Differentiated Services (Diffserv) Define per-hop behavior instead of end-to-end service model Support a small number of forwarding classes at each router. Forwarding class is encoded in the packet header. Problems with DiffServ: end-to-end service guaranteed is hard to maintain. 11/22/2018

Multi-Protocol Label Switching (MPLS): Originally designed for IP over ATM A short (fixed length) label is encoded for the packet header for packet forwarding Allow Label switched path (LSP) to be setup (explicit routing). allow datagram and virtual circuit to be coexisted in an IP network. MPLS can be combined with IntServ and DiffServ to support QoS. 11/22/2018

Comparison of IntServ and DiffServ Coordination for service differentiation End-to-End Local (per-Hop) Scope of service differentiation A Unicast or Multicast path Anywhere in a Network or a specific path Scalability Limitation by the number of flows Limited by the number of classes of service Network Accounting Based on flow characteristics and QoS requirement Based on class usage Network Management Similar to circuit Switching network Similar to existing IP networks Interdomain deployment Multilateral Agreements Bilateral Agreements 11/22/2018

COPS Definition Common Open Policy Service protocol IETF RAP working group To support policy control in an IP QoS environment Policy servers v.s. policy clients 11/22/2018

The COPS Role for Dynamic DiffServ Resource Allocation COPS protocol A simple query Response protocol that allows policy servers (PDPs, Policy Decision Point ) to communicate policy decisions to network devices (PEPs, Policy Enforcement Point ) To support multiple types of policy clients Uses to TCP to provide reliable exchange of messages Provides the means To establish and maintain a dialogue between the client and the server To identify the requests 11/22/2018

The COPS Role for Dynamic DiffServ Resource Allocation(2) Two main model Outsourcing model Provisioning model Events Bandwidth broker (policy decision point) Query (2) Notifications Trigger Events (1) Bandwidth broker (policy decision point) Response (3) Configuration commands Edge router (policy enforcement point) Edge router (policy enforcement point) Trigger events generate queries and responses Trigger events, notifications, and configuration commands are asynchronous Outsourcing and provisioning models in COPS 11/22/2018

The COPS Role for Dynamic DiffServ Resource Allocation(3) The dynamic scenario for DiffServ QoS An admission control framework To use server to control the admission of traffic within a DiffServ domain  Bandwidth Broker The use of COPS for the communication between the edge device and the BB COPS extensions for DiffServ resources allocation under outsourcing model 11/22/2018

The COPS Role for Dynamic DiffServ Resource Allocation(4) Signaling mechanism The QoS client to make resource reservation requests to the network RSVP End-to-end protocol to support multicast sessions spanning the whole Internet with receiver-oriented reservations More complex The European IST project AQUILA More systematic approach to address this problem 11/22/2018

The COPS Role for Dynamic DiffServ Resource Allocation(5) Bandwidth broker QoS client (H323 gatekeeper,SIP server…) PDP PEP COPS PDP PEP QoS-enabled network COPS Edge router COPS support to dynamic DiffServ-based IP QoS 11/22/2018

Definition of the COPS Interface The extension of COPS For dynamic DiffServ QoS scenario COPS-DRA : DiffServ Resource Allocation COPS-ODRA : Outsourcing DRA Based only on the outsourcing model For flexibility and efficiency In combination with providing model 11/22/2018

Definition of the COPS Interface The PEP always explicitly asks the PDP/BB for a given amount of resources For scalability Per-flow state is not stored in PDP/BB Resource allocation requests are properly aggregated Aggregate state information is kept in PDP/BB Provisioning model More scalable Inflexibility : difficult to handle modification of config. Not explicitly customized to handle dynamic DiffServ QoS 11/22/2018

Definition of the COPS Interface Requirements for a combined model The capability of provisioning resource to local nodes, in order to avoid high signaling burden Easy for the local node to request the modification of the provisioned resource Possible to handle specific requests under the outsourcing model 11/22/2018

Definition of the COPS Interface Three components of the reserv. Requests The scope and amount of reservation Where the reservation applies How much bandwidth The type of requested service Possibly including a set of QoS parameters The flow identification To which IP flow or aggregate of flows the reservation applies More complex scenarios may require more parameters Ex : timing 11/22/2018

Definition of the COPS Interface Bandwidth broker (1) PDP (4) (2) PDP PEP PEP PDP (3) (5) (6) QoS-enabled network An example information exchange using COPS-DRA 11/22/2018

IP telephony : A COPS Based QoS model SIP protocol Defined within the IETF Initiate voice, video, and multimedia sessions Candidate for call setup signaling in IP telephony IntServ-based approaches Client is customized for specific QoS mechanism. Terminal has to implement SIP and QoS reservation protocol. 11/22/2018

IP telephony : A COPS Based QoS model The main idea To eliminate the need for a specific QoS protocol in the terminals To use SIP as the sole call setup protocol All the QoS-related functions can be moved from the terminal to local SIP proxy servers To relieve the terminals of unneeded complexity and preserving backward compatibility 11/22/2018

Q-SIP Architecture No specific QoS protocol required. Terminal implementation is simplified. QoS Access Point QoS Access Point COPS/Other Client network COPS/Other Client network SIP SIP Q-SIP SIP terminal Q-SIP proxy server Q-SIP proxy server SIP terminal QoS SIP architecture 11/22/2018

Asymmetric Q-SIP Architecture Variant scenarios QoS Access Point QoS Access Point Client network COPS/Other COPS/Other Client network SIP SIP Q-SIP Q-SIP proxy server Q-SIP terminal SIP proxy server SIP terminal QoS SIP architecture 11/22/2018

A Q-SIP Architecture using COPS Based QoS model Bandwidth Broker(BB) PDP Qos signaling (COPS) COPS-DRA Qos-enabled network Client network PDP PEP PEP PDP Client network COPS-DRA COPS-DRA Access edge router Access edge router SIP SIP Q-SIP SIP terminal SIP terminal Q-SIP proxy server Q-SIP proxy server QoS SIP architecture Application signaling (SIP) 11/22/2018

A COPS Based QoS model QoS SIP architecture The edge routers Implement all mechanisms needed to perform admission control decision and policing function COPS protocol Used to make QoS reservation requests to the QoS access points 11/22/2018

A COPS Based QoS model(Cont.) SIP server To exchange message between the clients To add QoS related information in the SIP messages To negotiate QoS parameters among them Interact with the network QoS mechanisms Q-SIP Enhanced SIP ( QoS-enable SIP server ) 11/22/2018

Message Flow DiffServ network INVITE INVITE(With QoS-Info) INVITE Called user Q-SIP server SIP terminal Called user ER Bandwidth broker INVITE INVITE(With QoS-Info) INVITE 180 ringing 180 ringing 180 ringing 200 OK Cops REQ Cops REQ Cops DEC Cops DEC (With QoS-Info)200 OK Cops REQ Cops REQ Cops DEC Cops DEC 200 OK ACK ACK ACK <Traffic stream> 11/22/2018

QoS Info recorded in Q-SIP QoS info. is inserted into new INVITE messages or 200 OK response message: QoS-Info: <qos-param> *(;<qos-param>) Same info can also be carried by “Record-Route” header. Example of QoS-Info: QoS-Info: qos-domain=coritel.it; er-ingress=192.168.77.5; qos-mode=unidirectional 11/22/2018

QoS Info recorded in Q-SIP(Cont.) <qos-mode> Either “unidirectional” or “bidirectional” <er-ingress> & <er-egress> The edge router on caller/callee side <qos-domain> Identify the domain where resource reservation is done <caller-media-addr> & <caller-media-port> Caller address <other> 11/22/2018

Implementation Testbed The overall testbed scenario 11/22/2018

Implementation Testbed the QoS and call setup aspects two Ethernet based client networks Based on Linux OS COPS clients/servers A DiffServ core network Two ERs & one core router PDP/BB Access network One SIP terminal & one Q-SIP server 11/22/2018

Implementation Testbed Q-SIP server, ER, and BB internal architecture 11/22/2018

Conclusions Signaling mechanism Resource admission control within DiffServ Resource requests to a QoS provider QoS-aware call setups for SIP-based applications 11/22/2018

Conclusions (Cont.) Resource admission control within DiffServ PEP (Edge Router) Handles resource & policy enforcement PDP (Bandwidth Broker) Handles resource allocation pecisions 11/22/2018

Conclusions (Cont.) Resource requests to a QoS provider PEP (SIP proxy server) Asks for QoS reservation PDP (edge router) Typically edge routers of the DiffServ network 11/22/2018

Conclusions (Cont.) QoS-aware call setups for SIP-based applications Integrating the SIP signaling with DiffServ QoS mechanisms Preserving backward compatability. 11/22/2018

Reference S. Salsano, L. Veltri, Qos Control by Means of COPS to Support SIP-Based Applications X. Xiao, L. M. Ni, Internet QoS: A Big Picture S. Mallenius, The COPS (Common Open Policy Service) Protocol S. Salsano, L. Veltri, SIP Extensions for QoS support, <draft-veltri-sip-qsip-01.txt> http://www.coritel.it/projects/cops-bb 11/22/2018