Protocols with QoS Support

1. INF5070 – Media Servers and Distribution Systems: Protocols with QoS Support 27/9 - 2004

2. Overview • Quality-of-Service • Resource reservation • Protocols: • IPv4 • IPv6 • Tenet • ATM • IntServ • RSVP • DiffServ • MPLS • …

3. Quality-of-Service

4. Quality–of–Service (QoS) – I • Many definitions, e.g.:“QoS represents the set of those quantitative and qualitativecharacteristics of a distributed multimedia system that are necessary to achieve the required functionality of an application” Vogel et. al.: “Distributed Multimedia and QoS: A Survey”, IEEE Multimedia 1995

5. resources reserved C time Quality–of–Service (QoS) – II • Different semantics or classes of QoS: • determines reliability of offered service • utilization of resources max reserved B unused available resources reserved A

6. Quality–of–Service (QoS) – III • Best effort QoS: • system tries its best to give a good performance • no QoS calculation (could be called no effort QoS) • simple – do nothing • QoS may be violated  unreliable service • Deterministic guaranteed QoS: • hard bounds • QoS calculation based on upper bounds (worst case) • premium better name!!?? • QoS is satisfied even in the worst case  high reliability • over-reservation of resources  poor utilization and unnecessary service rejects • QoS values may be less than calculated hard upper bound

7. Quality–of–Service (QoS) – IV • Statistical guaranteed QoS: • QoS values are statistical expressions (served with some probability) • QoS calculation based on average (or some other statistic or stochastic value) • resource capabilities can be statistically multiplexed  more granted requests • QoS may be temporarily violated  service not always 100 % reliable • Predictive QoS: • weak bounds • QoS calculation based previous behavior of imposed workload • resource capabilities can be statistically multiplexed  more granted requests • possibly more exact workload description (if past and actual behavior matches) • QoS may be temporarily violated  service not 100 % reliable • QoS values may be less than calculated hard upper bound

8. Resource Reservation

9. Resource Reservation – I • Reservations is fundamental for reliable enforcement of QoS guarantees • per-resource data structure (information about all usage) • QoS calculations and resource scheduling may be done based on the resource usage pattern • reservation protocols • negotiate desired QoS by transferring information about resource requirements and resource usage between the end-systems and the intermediate systems participating in the data transfer • reservation operation • calculate necessary amount of resources based on the QoS specifications • reserve resources according to the calculation (or reject request) • resource scheduling • enforce resource usage with respect to resource administration decisions

10. Resource Management Phases Phase 1: user’s QoS requirements specification time rejection or renegotiation admission test and calculation of QoS guarantees negotiation resource reservation QoS guarantees to user confirmation renegotiation Phase 2: data transmission QoS enforcement by proper scheduling enforcement not necessary an own phase, some protocols start sending at once monitoring and adaptation “notification” renegotiation Phase 3: stream termination resource deallocation termination

11. Reservation Directions sender • Sender oriented: • sender (initiates reservation) • must know target addresses (participants) • in-scalable • good security 1. reserve data flow 2. reserve 3. reserve receiver

12. Reservation Directions sender • Receiver oriented: • receiver (initiates reservation) • needs advertisement before reservation • must know “flow” addresses • sender • need not to know receivers • more scalable • in-secure 3. reserve data flow 2. reserve 1. reserve receiver

13. Reservation Directions sender • Combination: • start sender oriented reservation • additional receivers join at routers(receiver based) 1. reserve data flow 2. reserve reserve from nearest router 3. reserve receiver

14. Routing

15. Routing application transport network link physical

16. Routing 209.73.164.90 216.239.51.101 192.67.198.54 80.91.34.111 129.42.16.99 129.240.148.31 81.93.162.20 209.189.226.17 193.99.144.71 66.77.74.20 129.240.148.31

17. … - … 216.239.51.101 - IF1 209.189.226.17 - IF2 80.91.34.111 - IF3 209.189.226.* - 209.189.226.17 129.240.* - 80.91.34.111 81.93.* - 80.91.34.111 192.67.* - 80.91.34.111 209.73.* - 80.91.34.111 129.240.148.* - 80.91.34.111 193.99.* - 80.91.34.111 66.77.74.20 - 80.91.34.111 … - … Routing 216.239.51.101 192.67.198.54 209.73.164.90 80.91.34.111 129.42.16.99 209.189.226.17 129.240.148.31 81.93.162.20 66.77.74.20 129.240.148.31 193.99.144.71

18. Routing 216.239.51.101 192.67.198.54 209.73.164.90 80.91.34.111 129.42.16.99 209.189.226.17 129.240.148.31 81.93.162.20 66.77.74.20 129.240.148.31 193.99.144.71

19. Protocols

20. Internet Protocol version 4 (IPv4) – I • IP is THEnetwork layer protocol within the Internet • IPv4 • defined by RFC 791 (1981) – STD 5 • unreliable datagram service (neither flow nor error control) • no fixed routes • flexibility for path selection • reordering problems • not suitable for time critical continuous media data • but, source routing is optional • loose – specify some router IP addresses to be passed in order • strict – specify all routers to be passed in order • maximum 64 KB datagrams including headers • segmentation for smaller subnets (e.g., 1500 B for standard Ethernet) • reassembly in end-system’s IP-layer

21. Internet Protocol version 4 (IPv4) – II indication of the abstract parameters of thequality of service desired – somehow treat high precedence traffic as more important – tradeoff between low-delay, high-reliability, and high-throughput – NOT used, bits now reused indicates the format of the internet header, i.e., version 4 length of the internet header in 32 bit words, and thus points to the beginning of the data (minimum value of 5) datagram length (octets) includingheader and data - allows the lengthof 65,535 octets fragments allowed flag allowed and last fragment flag 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| IHL |Type of Service| Total Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identification |Flags| Fragment Offset | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Time to Live | Protocol | Header Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ identifying value to aid assembly of fragments indicate where this fragment belongs in datagram disable a packet to circulate forever,decrease value by at least 1 in each node – discarded if 0 checksum on the header only – TCP, UDP over payload. Since some header fields change(TTL), this is recomputed and verified at each point indicates used transport layer protocol 32-bit address fields. May be configured differently from small to large networks options may extend the header. If the options do not end on a 32-bit boundary, the remaining fields are padded in the padding field (0’s)

22. Internet Protocol version 6 (IPv6) – I the 4-bit priority field has been replaced by an 8-bit traffic class field. To identify and distinguish between different classes or priorities disable a packet to circulate forever, decrease value by at least 1 in each node – discarded if 0 • IPv6 • defined by RFC 1883 (1995), but revised by RFC 2460 (1998) • simplified header: label packets which requests special handling by the IPv6 routers, such as non-default quality of service or real-time +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Prio. | Flow Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Length | Next Header | Hop Limit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Source Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Destination Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Traffic Class | Flow Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Length | Next Header | Hop Limit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Source Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Destination Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ version of protocol, i.e., version 6 length of payload in bytes. If zero, indicates that the payload length is carried in a Jumbo Payload option. Identifies the type of headerimmediately following the header – e.g., TCP, UDP, but also EXTENSION headers 128-bit address fields

23. Internet Protocol version 6 (IPv6) – II • IPv6 • enlarged address space (2128 = 3.4 x 1038 addresses) • simplified headers reduce packet processing time • “jumbograms” allows packets larger than 64 KB (using a extension header) • strict routing (source can fix route to destination using a routing extension header) • inclusion of security concepts and mobile end-systems • may specify only a geographical range for a multicast session • some support for QoS concepts – each packet header includes ... • ... a 8-bit traffic class field – defined by DiffServ • ... a 20-bit flow label

24. Internet Protocol version 6 (IPv6) – IV • Flow labels • “a flow is a sequence of packets sent from the source to the destination for which the source desires special handling by the routers” • each flow must have same flow label, priority and addresses • flow = pseudo-connection • before start or during transmission • set up flow between source and destination • route is cached – table entries in a router allows fast packet switching • routers can reserve resources • during data transmission • routers can identify flows by a unique “flow label/address” combination • routers can treat packets according to the flow type • still experimental use • BUT; IPv6 itself does not define mechanisms for QoS treatment – must use additional protocols

25. IP Multicast • Limiting IP multicast geographically • IPv4 – interpretation of TTL header field is used(non-standardized MBONE use) • IPv6 – multicast address contains a 4-bit scope field • possible geographical limits • machine • LAN • organization • country (v4 only) • continent (v4 only) • global – no limit

26. Tenet – I • Late 80’s/early 90’s, Tenet group at Berkeley • Aims for network support for real-time continuous media applications • Real-time communication model • Real-time channels: end-to-end connection with performance guarantees and traffic restrictions • associated with a set of nodes and links (a route) through which real-time packets pass • resource reservation in route nodes • admission control

27. Tenet – II • Traffic specification: • expressing peak and average load on the network • indication of the burstiness of the load • parameters: • minimum packet inter-arrival time • average packet inter-arrival time • averaging interval • maximum packet size • Supported QoS parameters (by which users describe their requirements): • upper bound on end-to-end message delay • delay violation probability bound • buffer overflow probability bound • delay jitter bound (optional) • a throughput guarantee is obtained from the traffic specification

28. application Tenet – III real-time channeladministration protocol real-time messagetransport protocol continuous media transport protocol • Protocol suite: • Real-time Channel Administration Protocol (RCAP) • performs channel setup • uses the traffic description and performance requirementto find a route and maps the global requirement onto local resources • performs admission control and reservations on the way • Real-time Message Transport Protocol (RMTP) • intended for message based real-time transport • Continuous Media Transport Protocol (CMTP) • offers a stream based interface and a time-driven mechanism for audio and video – may demand data from application • Real-time Internet Protocol (RTIP) • replaces IP • schedules packets according to resource reservations made by RCAP real-timeinternet protocol data link layer physical layer

29. Asynchronous Transfer Mode (ATM) – I • Defined by ATM Forum and International Telecommunication Union (ITU) • Targeted for all kinds of traffic within the same network (i.e., both continuous and discrete data types) • A full suite of protocols: • physical layer – deals with voltages, bit timingand framing on the physical medium • ATM layer – defines the ATM cell structure • adaptation layer – analogous to the Internet transport layer supporting different services • Today: “IP-over-ATM” • IP rules – TCP/IP is used in every end-system ATM used as link-layer technology • however, ATM may forward data quickly • ATM may be used in the Internet backbone running under IP • uses AAL5 to transport IP datagrams over the ATM network ATM adaptation layer (AAL) ATM layer ATM physical layer

30. Asynchronous Transfer Mode (ATM) – II • Service classes • constant bit rate (CBR)(real-time, guaranteed constant rate) • variable bit rate (VBR) – real-time and non-real-time • available bit rate (ABR)(slightly better than best effort – a minimum guarantee, only class with congestion control) • unspecified bit rate (UBR)(best effort, no guarantees) • Virtual channels (VC) • the ATM network sets up a VC between sender and receiver • a path consisting of a sequence of links • each link has a virtual circuit identifier (VCI) used for routing(included in the cell header) • ATM backbones usually use permanent VCs, i.e., saving VC setup and teardown • Virtual paths

31. cannot be negotiated – part of network QoS offer Asynchronous Transfer Mode (ATM) – III • The ATM standard specifies a number of QoS parameters • traffic generation by sender: • cell rate (sustainable (SCR) / peak (PCR) / minimum (MCR)) • maximum burst size (MBS) • cell delay variation tolerance (CDVT) • service provided by network: • cell transfer delay (CTD) – cell transit time from source to destination • cell delay variation (CDV) – variance in transfer delays • cell loss ratio (CLR) – fraction of cells lost or delivered too late • cell error rate (CER) – fraction of cells with bit errors • severly-errored cell block ratio (SECBR) – fraction of an N-cell block with M or more cells damaged • cell misinsertion rate (CMR) – number of cells delivered to wrong destination

32. Asynchronous Transfer Mode (ATM) – VI • Traffic contracts • the VC acts like a contract between customer and network for a service • consist of a connection traffic descriptor and a set of QoS parameters • which traffic to be offered • which service class • compliance requirements • the QoS parameters are negotiated during the VC setup (can be specified either explicitly or implicitly)

33. Asynchronous Transfer Mode (ATM) – V • Different service categories require different parameters

34. Asynchronous Transfer Mode (ATM) – VI • Application areas for ATM service categories (by ATM Forum) 3 – good 2 – fair 1 – not good, not applicable with advantage n/s – not suitable may be more useful now!!??

35. Integrated Services (IntServ) – I • Framework by IETF to provide individualized QoS guarantees to individual application sessions • Goals: • efficient Internet support for applications which require service guarantees • fulfill demands of multipoint, real-time applications (like video conferences) • do not introduce new data transfer protocols • In the Internet, it is based on IP (v4 or v6) and RSVP (described later) • Two key features • reserved resources – the routers need to know what resources are available (both free and reserved) • call setup (admission call) – reserve resources on the whole path from source to destination

36. Integrated Services (IntServ) – II receiver • Admission call: • traffic characterization and specification • one must specify the traffic one willtransmit on the network (Tspec) • one must specify the requested QoS(Rspec – reservation specification) • signaling for setup • send the Tspec and Rspec to all routers • per-element admission test • each router checks whether the requestsspecified in the R/Tspecs can be fulfilled • if YES, accept; reject otherwise sender 1. request: specify traffic (Tspec), guarantee (Rspec) 1 3 2. consider request against available resources 3. accept or reject 2

37. Integrated Services (IntServ) – III • IntServ introduce two new services enhancing the Internet’s traditional best effort: • guaranteed service • guaranteed bounds on delay and bandwidth • for applications with real-time requirements • controlled-load service • “a QoS closely to the QoS the same flow would receive from an unloaded network element” [RFC 2212], i.e., similar to best-effort in networks with limited load • no quantified guarantees, but packets should arrive with “a very high percentage” • for applications that can adapt to moderate losses, e.g., real-time multimedia applications

38. Integrated Services (IntServ) – IV • Both service classes uses token bucket to police a packet flow: • packets need a token to be forwarded • each router has a b-sized bucket with tokens:if bucket is empty, one must wait • new tokens are generated at a rate r and added:if bucket is full (little traffic), the token is deleted • the token generation rate r serves to limit the long term average rate • the bucket size b serves to limit themaximum burst size token generation bucket token wait queue

39. Integrated Services (IntServ) – V • Usual protocol structure: application RTP RSVP UDP IP data link

40. Resource Reservation Protocol (RSVP) - I • Defined by RFC 2205 (1997) • A protocol to signal reservations of resources in the Internet • contains protocol elements for control • no support for data transfers (reservation signals only) • simplex protocol, i.e., makes reservations for unidirectional flows • receiver-oriented, i.e., the receiver initiates and maintains resource reservations • maintains a “soft” state – graceful changes to dynamic memberships and automatic adaptation to route changes (timeouts) • companion protocol to IP – supports both IPv4 and IPv6 • transported as raw IP datagram with protocol number 46 • filtering provides support for heterogeneous receivers and different reservation styles

41. Resource Reservation Protocol (RSVP) - II • RSVP will generally require raw network I/O • sends raw IP datagrams using protocol 46 • operates on top of IP, i.e., takes the place of the transport protocol • does not perform traditional transport layer services – must add a transport protocol (UDP) application UDP RSVP IP data link

42. same multicast group and port Resource Reservation Protocol (RSVP) - III • Sessions • a data flow with particular destination and transport protocol • defined by (destination address, protocol ID) • IP address • IP protocol ID • may carry multiple data flows • Data flows are distinguished by • source IP address and source port (IPv4) • source IP address and flow label (IPv6) • Transmission model:

43. flow descriptor Resource Reservation Protocol (RSVP) - IV • Two fundamental messages: • PATH: • sender sends a PATH message downstream following the data path • sent using same source and destination addresses • includes: • hop-addresses • sender template (describes data packet format) • sender Tspec (traffic characteristics generated by sender) • sender Adspec (advertisement information) • ... • RESV: • receiver sends a RESV message upstream using the path described in the PATH message • sent to previous hop only • includes: • flowspec: reservation requests, desired QoS (e.g., RFC 1363) • filterspec: reservation style • reverse data paths for the flow • ...

44. Resource Reservation Protocol (RSVP) - V • Creating and maintaining a reservation state: • the SOURCE • multicasts data flows • sends PATH messages with traffic characteristics (Tspec) describing flows • the RECEIVER • joins multicast group • receives the PATH message • determines own QoS requirements based the PATH Tspec • sends a RESV message with request and filters • the ROUTERS • reserve according to incoming flowspecs downstream • merge and forward the RESV messages to next node using largest flowspec • the reservations are maintained using “soft” states • the reservation has an associated timer – a timeout removes the reservation • periodically refreshed by PATH and RESV messages

45. Resource Reservation Protocol (RSVP) - VI 10 Mbps 1 Mbps RESV10 Mbps RESV1 Mbps reserved 10 Mbps merging merging merging reserved 1 Mbps PATH PATH PATH PATH PATH reserved 10 Mbps reserved 10 Mbps reserved 1 Mbps PATH RESV10 Mbps RESV10 Mbps RESV1 Mbps 5 Kbps PATH reserved 5 Kbps reserved 3 Mbps RESV5 Kbps RESV3 Mbps merging PATH PATH PATH reserved 3 Mbps reserved 3 Mbps RESV3 Mbps RESV3 Mbps reserved 1 Mbps RESV1 Mbps 3 Mbps 1 Mbps

46. Resource Reservation Protocol (RSVP) - VII • RSVP in hosts and routers: • RESV with flowspec and filterspec to RSVP daemon • policy control to check privileges etc. • admission control using flowspec • forward RESV message • control of local modules: classifier and scheduler application process RSVPdaemon policy control routing process RSVPdaemon policy control admission control admission control packet classifier packet scheduler packet classifier packet scheduler data

47. Resource Reservation Protocol (RSVP) - VIII • Reservation styles • a reservation request includes a set of options called the reservation style • shared vs. distinct reservations • concerns treatment of reservations of different senders • shared – single reservation for all senders (e.g., video conference audio) • distinct – one reservation per sender (e.g., video conference video) • explicit vs. wildcard • concerns selection of senders • explicit – specify senders (e.g., teleteaching) • wildcard – automatically select all senders (e.g., video conference)

48. Resource Reservation Protocol (RSVP) - IX

49. Resource Reservation Protocol (RSVP) - X • The RSVP standard [RFC 2205] allows to reserve link bandwidth – it does NOT...: • ...define how the network should provide the reserved bandwidth to the data flows – the routers must implement these mechanisms themselves • ...specify how to do resource provisioning – which must likely be done using a proper scheduling mechanism • ...determine the route – it is not a routing protocol, but relies on others • ...determine which data to drop in case of overflow, i.e., the most important data may be lost • ...perform an admission test, but it assumes that the routers perform admission control • THUS; RSVP can only be used as a small piece in the QoS guarantee puzzleKurose, J. F., Ross, K. W.: “Computer Networking: A Top-Down Approach Featuring the Internet”, 2nd edition, Addison Wesley, 2002

50. Differentiated Services (DiffServ) – I • IntServ and RSVP provide a framework for per-flow QoS, but they … • … give complex routers • much information to handle • … have scalability problems • set up and maintain per-flow state information • periodically PATH and RESV messages overhead • … specify only a predefined set of services • new applications may require other flexible services • DiffServ [RFC 2475] tries to be both scalable and flexible