Advanced Computer Networks1 Providing Guaranteed Services Without Per Flow Management By: Ion Stoica, Hui Zhang Presented by: Sanjeev R. Kulkarni

Advanced Computer Networks2 Outline Problems with the current QoS architectures Stateless Core Architecture(SCORE) –Dynamic Packet State –Core Jitter Virtual Clock Algorithm –Admission Control Implementation details Extensions to IPv6

Advanced Computer Networks3 Current QoS architectures Integrated Services Differentiated Services

Advanced Computer Networks4 Integrated Services All Routers maintain per-flow state State –Control Plane Admission Control: per flow signaling –Data Plane Classifier: per flow flow-ids scheduler: per flow scheduling algorithm parameters

Advanced Computer Networks5 Integrated Services All Routers maintain per-flow state State –Control Plane Admission Control: per flow signaling –Data Plane Classifier: per flow flow-ids scheduler: per flow scheduling algorithm parameters Scalability??

Advanced Computer Networks6 Jitter Virtual Clock For each packet –eligible time –deadline Scheduling done in the order of the deadline –e 1 i,j = a 1 i,j –e k i,j = max ( a k i,j + g k i,j-1, d k-1 i,j ) –d k i,j = e k i,j + l k i /r i

Advanced Computer Networks7 Core-routers and Edge routers

Advanced Computer Networks8 Differentiated Services A small number of traffic classes Only Edge routers maintain per flow state Control Plane Admission Control: per flow signaling Data Plane Classifier: per class classification Scheduler: per class scheduling

Advanced Computer Networks9 Differentiated Services A small number of traffic classes Only Edge routers maintain per flow state Control Plane Admission Control: per flow signaling Data Plane Classifier: per class classification Scheduler: per class scheduling Quality of QoS??

Advanced Computer Networks10 Stateless Core Solution Idea similar to DiffServ Only Edge Routers maintain per flow state Dynamic Packet State (DPS) is inserted into each packet by edge routers Core routers update DPS and schedule packets accordingly

Advanced Computer Networks11 DPS Ingress Egress

Advanced Computer Networks12 How it works a b c d

Advanced Computer Networks13 How it works a b c d

Advanced Computer Networks14 How it works a b c d

Advanced Computer Networks15 How it works a b c d

Advanced Computer Networks16 How it works a b c d

Advanced Computer Networks17 How it works a b c d

Advanced Computer Networks18 How it differs from DiffServ DPS versus Per Hop Behavior (PHB) –DPS is dynamic –Routers change DPS and schedule packets based on the DPS state –DPS change mirrors a Core-Jitter Virtual Clock scheduling

Advanced Computer Networks19 Core Jitter Virtual Clock –e k i,j = max ( a k i,j + g k i,j-1, d k-1 i,j ) The main culprit is d k-1 i,j Introduce a slack variable such that –a k i,j + g k i,j-1 + > d k-1 i,j i k =max (0, i k-1 + (l i k-1 - l i k )/r i - (e i,1 k - e i,1 k-1 - l i k-1 /r i )/(h-1) )

Advanced Computer Networks20 Example a b

Advanced Computer Networks21 Example a b ea1ea1 da1da1

Advanced Computer Networks22 Example a b ga1ga1 ea1ea1 da1da1

Advanced Computer Networks23 Example a b eb1eb1 db1db1 ea1ea1 da1da1 ga1ga1 ga1ga1

Advanced Computer Networks24 Example a b ea1ea1 da1da1 eb1eb1 db1db1

Advanced Computer Networks25 Example a b ea1ea1 ea2ea2 eb1eb1 db1db1 da2da2

Advanced Computer Networks26 Example a b ea2ea2 eb1eb1 db1db1 da2da2

Advanced Computer Networks27 Example a b ea2ea2 eb1eb1 db1db1 da2da2 ga1ga1 gb1gb1

Advanced Computer Networks28 The algorithm Parameter Initialization by Ingress Routers Core routers examine the parameters and modify g Egress Routers strip the packet of these labels

Advanced Computer Networks29 Admission Control s r d c b a

Advanced Computer Networks30 Admission Control Resv s r d c b a

Advanced Computer Networks31 Admission Control 1 s r d c b a

Advanced Computer Networks32 Admission Control s r d c b a

Advanced Computer Networks33 Admission Control s r d c b a

Advanced Computer Networks34 Admission Control s r d c b a

Advanced Computer Networks35 Admission Control 3 s r d c b a

Advanced Computer Networks36 Admission Control Resv s r d c b a

Advanced Computer Networks37 Admission Control Each core router maintains an upper bound R on the Total Bandwidth reserved Local Admission Control –Accept if R + r i < C Periodically they run an algorithm that contains the deviation between the actual B/w reserved and R.

Advanced Computer Networks38 Recalibration Algorithm Packet state b Add all b values on each packet arrival Periodically they update based on R = min ( R, R D /(1-f) + R new )

Advanced Computer Networks39 Implementation IPv4 Header TOS 11 Frag Offset

Advanced Computer Networks40 Implementation F1F2F3Flag 25916

Advanced Computer Networks41 Extension to Ipv F1F2F3Flag 31 Flow Label

Advanced Computer Networks42 Summary SCORE Network –Is Scalable –Gives a QoS similar to Jitter Virtual Clock –Extensible to Ipv6 –Transparent to the outside network