© Jörg Liebeherr, Quality-of-Service Architectures for the Internet Integrated Services (IntServ)

© Jörg Liebeherr, Components of a QoS architecture Source: CMU, S. Seshan, B. Maggs

© Jörg Liebeherr, Granularity of QoS Per-flow guarantees –Require per-flow reservations in the network –Require per-flow classification at routers

© Jörg Liebeherr, QoS Service Architectures for the Internet Two QoS architectures have been defined for Internet. –Integrated Services (IntServ) Proposed in 1994 Per-flow Quality of Service Resource reservation/admission control Can support delay guarantees –Differentiated Services (DiffServ) Proposed in 1998 Class-based QoS Resource reservation not always needed

© Jörg Liebeherr, Integrated Services IntServ specifies two types of services: Guaranteed Service –Guaranteed bandwidth –End-to-end delay bounds –No loss due to buffer overflows Controlled Load Service –Provides a service that is equivalent to a best effort service in a lightly loaded netework Low loss Low delay No absolute guarantees

© Jörg Liebeherr, Integrated Services 1.At network entrance: Policing and Shaping 2.Somewhere in the network: Admission Control 3.At switches: Classification, Scheduling 4.Between hosts and routers: Signaling FlowSpec (TSpec, RSpec) Distributed or Centralized Weighted Fair Queuing or other latency-rate algorithm RSVP in IntServ

© Jörg Liebeherr, Resource ReSerVation Protocol (RSVP) RSVP is a signaling protocol that enables senders, receivers, and routers of unicast or multicast sessions to communicate with each other for setting up state to support a service –Receiver-driven Resource reservation is initiated by receivers –Unicast and multicast sessions –Soft-state: state information of RSVP must be periodically refreshed Separate mechanisms required for authorization, authentication, and charging

© Jörg Liebeherr, RSVP Functional Diagram ApplicationRSVPD Admissions Control Packet Classifier Packet Scheduler Policy Control DATADATA DATA RSVPD Policy Control Admissions Control Packet Classifier DATA Routing Process HostRouter Source: Gordon Chaffee, UC Berkeley Packet Scheduler

© Jörg Liebeherr, Source: Cisco

© Jörg Liebeherr, RSVP Flowspec Peak Data Rate [p] Minimum Policed Unit [m] Maximum Policed Unit [M] Token Bucket Rate [r]... Token Bucket Size [b] Guaranteed Flowspec Rate [R] Slack Term [S] Source: Gordon Chaffee, UC Berkeley T-SPEC R-SPEC

© Jörg Liebeherr, Guaranteed Service A flow must perform a reservation request during a flow setup phase –Uses RSVP Traffic Specification (T-SPEC):  (t) = min (M + pt, rt + b) -M is max. packet size -p is peak rate -r is average rate -b is burst size Routers along a path accept or reject reservation

© Jörg Liebeherr, Latency-rate Schedulers Guaranteed service assumes that routers implement a latency-rate service curve with delay T and rate R: S(t) = R · (t – T) + with –T = L /R + D –L is the maximum packet size of this flow –D = L all / C is the maximum packet transmission time (preemption delay) »L all is maximum packet size at this link »C is the link capacity Router implementations (some in software): Cisco – WFQ Extreme Networks – WFQ, CBQ, DRR Nortel - CBQ

© Jörg Liebeherr, RSVP in IntServ Flow set-up: –advertisement with PATH message from source –contains TSPEC (p,M,r,b) of the source –contains ADSPEC (L tot, D tot ) which is updated on the path ADSPEC contains: L tot =  i L i D tot =  i D i –PATH does not result in reservations ! –ADSPEC is used by receiver to select reservation (p,M,r,b) ( )( ) (L 1, D 1 ) (L 1 +L 2, D 1 +D 2 ) Sender Receiver Source: P. Thiran

14 RSVP in IntServ Flow set-up: Receiver responds with a RESV message. RESV messages make the reservations at the node –Receiver writes the service level requested by receiver in an R-SPEC –R-Spec specifies the reserved rate R’ R’ is determined at the receiver using the formula: ((b-M)/R’) (p-R) + /(p-r) + (M +  i L i )/R’ +  i D i This assumes that all nodes reserve the same rate R n = R’. R’ is computed so that end-to-end delay bound <= delay objective. (p,M,r,b) ( )( ) (L 1, D 1 ) (L 1 +L 2, D 1 +D 2 ) R’ Source: P. Thiran

© Jörg Liebeherr, Call Admission Call Admission: routers will admit calls based on their R-spec and T-spec and base on the current resource allocated at the routers to other calls. Source: CMU, S. Seshan, B. Maggs

© Jörg Liebeherr, Reservation Merging Receiver #1 Receiver #2 Receiver #3 Reservations merge as they travel up tree. R6 R3 R1 R4 R7 (1) 50Kbs (2) 50Kbs (3) 50Kbs (4) 100 Kbs (5) 100 Kbs (6) 100 Kbs (7) 100 Kbs (8) 60Kbs (9) 60Kbs Source: Gordon Chaffee, UC Berkeley

© Jörg Liebeherr, Summary of IntServ –Advantages: Strong guarantees (bounded delays) –Disadvantages: Requires that all routers implement IntServ Scalability concerns since routers must maintain state information Charging and authentication of reservations must be solved Interdomain issues are difficult to resolve