1. 1 Presentation_ID © 1999, Cisco Systems, Inc. IP QoS Basics Peter Tomsu Senior Consultant Cisco Systems EMEA ptomsu@cisco.com Peter Tomsu Senior Consultant Cisco Systems EMEA ptomsu@cisco.com

2. 2 Presentation_ID © 1999, Cisco Systems, Inc. 2 Presentation_ID © 1999, Cisco Systems, Inc. www.cisco.com IP QoS

3. 3oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com QoS—Optimizing Throughput 30 Kbps 300 Kbps Bursty applications contending for bandwidth reduce collective throughput better throughput needed What can we do to improve things?

4. 4oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Internet Classification and marking of packets at the edge of the network makes the packets accessible to QoS handling within the network Network Management Classifying and Marking

5. 5oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Internet Optimized queueing and forwarding in the core of the network (PHB – Per Hop Behavior) allows for fast efficient delivery Optimized Forwarding

6. 6oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Architecture for Differentiated Services RFC 2475 An Architecture for Differentiated Services Dec 98 defines an architecture for implementing scalable service differentiation in the Internet !

7. 7oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com DSCP DSCP : Differentiated Service Code Point = 6 bits CU: Currently Unused = 2 bits (lined up for ECN) DSCP is the field identifying what treatment the packet should receive DSCPCU DS field

8. 8oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Diff-Serv Traffic Conditioner Classifier selects a pkt in a traffic stream based on the content of some portion of the pkt header Meter checks compliance to traffic parameters (eg Token Bucket) and passes result to marker and shaper/dropper to trigger particular action for in/out-of-profile packets Marker Writes/rewrites DSCP Shaper delay some pkts for them to be compliant with the profile Pkts Classifier Meter Marker Shaper/ Dropper Shaped Dropped

9. 9oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Per-Hop Behavior Per Hop Behavior (PHB) description of the externally observable forwarding behavior of a DS node applied to a the set of packets with the same DSCP PHB may be defined in terms of DS nodes resources priority relative to other PHBs observable traffic characteristics (delay, loss, …) PHBs are defined as “black box” does NOT mandate particular implementation mechanisms ! Different boxes implement PHBs in different ways which are optimised for each platform As long as it complies with “black box” spec, this is perfectly fine

10. 10oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Default PHB RFC2474, Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers, Dec 98 Default PHB good old Best-effort behavior Recommended DSCP: “000000” Note: Each PHB has a “recommended” DSCP value but ISPs can use a different value in their network

11. 11oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com EF PHB Definition RFC 2598 Expedited Forwarding PHB, June 99 EF PHB can be used to build a low loss, low latency, low jitter, assured bandwidth, end-to-end service – targets VoIP, Virtual Leased Lines – Assured traffic sees no (or very small) queues/delay – Constraint: Requires bounding rates such that, at every transit node, the aggregate’s max arrival rate is less than the aggregate min departure rate An example of how EF can be implemented is a PQ (with rate limit). Recommended DSCP=101110

12. 12oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com AF PHB Group Definition RFC2597, Assured Forwarding PHB Group, June 99 different levels of forwarding assurances for IP packetsAssured Forwarding (AF) PHB Group is meant to offer different levels of forwarding assurances for IP packets received from a customer DS domain Olympic Service (Gold, Silver, Bronze) gold (C1) >= silver (C2) >= bronze (C3) No quantifiable timing requirements! delay or delay variation

13. 13oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com AF PHB Group Definition Currently definedCurrently defined independently 4 independently forwarded AF classes (ie 4 “queues” and 4 virtual networks with independent capacity management) Within each AF class, 3 levels of drop precedence Within each AF class, RED-like buffer mgt DS node should implement all 4 general AF classes DS node must allocate a configurable minimum amount of forwarding resources to each implemented AF class AF Class 1: 001dd0 AF Class 2: 010dd0 AF Class 3: 011dd0 AF Class 4: 100dd0 dd= drop precedence Recommended DSCP:

14. 14oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Cisco’s Diff-Serv Implementation ToS - Pre-Diff-Serv implementation (IP Precedence) not RFC compliant DS-byte encoding (RFC2474) Diff-Serv Architecture (RFC 2475) Default Forwarding Class Selectors Expedited Forwarding Assured Forwarding Data IP Precedence Type of Service (ToS) Diff-Serv Code Point (DSCP) Data, Voice, Video

15. 15oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Diff-Serv Functional Blocks ClassifierConditionerForwardingPHB Metering Dropping Marking Shaping Accounting Scheduling Discard ACL QPPB CAR TS Netflow CEFCBWFQ PQ WRED Implementation Features

16. 16oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com IP Precedence Setting Techniques MQC – Modular QoS CLI (12.0(5)T) Policy-Based Routing Fast-switched since Release 11.3 QoS Policy Propagation with BGP (QPPB) Committed Access Rate (CAR) Inbound / outbound Dial peers (Voice over X)

17. 17oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com What Is Modular QoS CLI (MQC)? Modular QoS CLI (MQC): Is how you configure QoS policy Separates the definition of classes from the application of QoS mechanisms MQC is template-based: Reduces configuration Configure policy, not “raw” per-interface commands

18. 18oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com QoS Policy Propagation via BGP Service Provider or Large Enterprise Network Advertises route, community attribute=X Advertises route, community attribute=Y Community attribute used to set precedence/DSCP for return traffic

19. 19oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Committed Access Rate (CAR) Two functions Packet Classification Packet Classification — sort a subset of traffic matching some complex criteria Traffic Conditioning Traffic Conditioning rate measurement, rate limiting, packet marking (IP Precedence rewrite)

20. 20oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Drop Per Application CAR Multimedia Mission-Critical Recolor CAR—Policy Examples

21. 21oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Car Overview TrafficMatchingSpecification Next Policy ActionPolicy TrafficMeasurementInstrumentation

22. 22oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com CAR—Traffic Matching Specification Identify packets of interest for packet classification or rate limiting or both Matching specification 1) 1) All traffic 2) 2) IP precedence 3) 3) MAC address 4) 4) QoS group 5) 5) IP access list—Standard and extended (slower)

23. 23oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Token Bucket p Tokens B Overflow Tokens Packets Arriving Conform Exceed B B—Burst Size p p—Token Arrival Rate

24. 24oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Extended Burst Exceed % 100 Bucket Depth Extended Burst Normal Burst

25. 25oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com CAR Ingress Router Packet Classification Rate Limiting Committed Rate Burst RED-like Managed Drop Egress Router Packet Classification (Reset Precedence Bits) Rate Limiting Committed Rate Burst RED-like Managed Drop L3 CAR 502 flefauch@cisco.com NW’98 25 © 1998, Cisco Systems, Inc.

26. 26oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com StandardPremium Weighted Random Early Detection Upon congestion, packets from lower precedence are selectively discarded first Minimize the congestion impact on higher precedence services anim

27. 27oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Weighted RED Packet Drop Probability Queue Length “Slope” is adjustable Queue Max Packet Drop Probability Queue Length Queue Max Packet Drop Probability Queue Length Standard Service Queue Max Without RED With RED With WRED Premium Service Std. Min.Prem. Min.

28. 28oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Priority Queuing (PQ) Rigid traffic prioritization scheme with 4 queues—high, medium, normal, low Traffic assigned to queues via previously defined priorities and policies Unclassified packets are placed in the normal queue Interface Buffer Resources Transmit Queue Output Line High Medium Normal Low Classify Absolute Priority Scheduling

29. 29oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Custom Queuing (CQ) Flexible traffic prioritization scheme that allocates a minimum bandwidth to specified types of traffic Up to 16 queues available Queues serviced in round-robin fashion Interface Buffer Resources Up to 16 3/10 1/10 Weighted Round Robin Scheduling (byte count) Allocate Proportion of Link Bandwidth) Classify 2/10 3/10 2/10 Transmit Queue Output Line

30. 30oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Weighted Fair Queuing Discriminates between CoS Aggregate guaranteed bandwidth allocated to each CoS Excess bandwidth shared by all CoS’s (based on weight) High scalability/performance COS 1COS 2 COS 3 COS 4 Gold Gets at least 40% of bandwidth Standard Gets at least 10% of bandwidth Silver Gets at least 30% of bandwidth Bronze Gets at least 20% of bandwidth

31. 31oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Class-Based WFQ (CBWFQ) “Classes” have an associated bandwidth in Kbps Traffic assigned to classes via match criteria Protocol, interface, or access lists Maximum of 64 classes which support: Bandwidth allocation (guarantees) per class RED/WRED per class Unclassified traffic can either: Have a fixed allocated BW (use class-default with “bandwidth”), or Be treated by a standard WFQ system (use class- default with “fair”)

32. 32oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Class-Based WFQ—QoS Guarantees and Bandwidth Efficiency Weights guarantee minimum bandwidth Buffering controls latency Unused capacity is shared amongst the other classes Each queue can be separately configured for QoS Benefits Maximize transport of paying traffic No loss of service class guarantees No wasted bandwidth as with PVCs 40% 25% 10% Gold Silver Bronze Step 1: Define Buffering Step 2: Define Bandwidth Guaranteed: Latency, Delivery Guaranteed: Delivery Best Effort

33. 33oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com PQ-WFQ (IP RTP Priority) WFQ Interface 33 33 22 43211 VV 44 44 PQ WAN Circuit Exhaustive Queuing WFQ DLCI 33 33 2L PQ - voice WFQ - Data 44 44 PQ WAN Circuit WFQ - Data Interface High Low LMI 11 VV 432 43L 1 V 1 V L 1 1 VV 2 1 1 VV PQ - voice WFQ - Data Leased Lines Frame Relay

34. 34oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Low Latency Queuing (LLQ) CBWFQ does not effectively handle real- time traffic well on its own LLQ adds a priority queue to CBWFQ specifically for priority traffic only Supports VoIP on serial and ATM PVCs only VoIP over Frame Relay is not supported VoIPoFR as of 12.1(2)T

35. 35oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Difference Between IP RTP Priority and LLQ? IP RTP Priority Does not need CBWFQ, but can be combined with it Configured on interface When using voice ports, gives priority to even ports (actual call) within specified range only LLQ Configured as part of CBWFQ priority maps When using voice ports, gives priority to both odd (RTCP control) and even (actual call) ports Note: the initial call control is TCP traffic

36. 36oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Transmit Queue Output Line Traffic Destined for Interface Classification by: Extended Access List Functionality “Leaky Bucket” Shaping Configured Queuing (WFQ, PQ, and so on) Match No Match Classify (Generic) Traffic Shaping

37. 37oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Link Fragmentation and Interleaving (LFI) LFI fragments large datagrams and interleaves them with low-delay traffic packets Transmit Queue Output Line Traffic Destined for Interface Large Packet Fragmentation: Fragment Size Based on Required Delay WFQ Multlink PPP with LFI on Jumbogram IP Voice

38. 38oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Compressed Real-Time Transport Protocol (cRTP) Configured Queuing Traffic Destined for Interface Identify RTP Traffic Compression RTP Traffic (Video, Audio, and so on) Classify RTP Compressor Non-RTP Transmit Queue Output Line VoIP SQL FTP 20 Byte 256 Byte 1,500 Byte Efficiencies Payload Packet Size Reduction* *Also ~5 ms Reduction in serialization delay at 64 Kbps ~ 240% ~ 13% ~ 2.3% RTP 12 UDP 8 IPH 20 5 IP Data

39. 39oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com IntServ Over DiffServ Framework describing how to achieve end-to-end Int-Serv in the presence of Diff-Serv clouds Key to scaling RSVP both in Enterprise and SP Mapping of RSVP flows onto PHBs Multiple Alternatives for Admission Control over DS Cloud No Admission Control Admission Control AT EDGE ONLY Admission Control at every hop in DS cloud Admission Control at every hop in DS cloud BUT via Aggregated Resevations Handset PBX Server IntServ e2e DiffServ

40. 40oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com QoS Admin Console Policy Server Policy Servers Policies Application Servers RSVP: Vehicle for Policy Based Networking LDAP Directory COPS DNS/DHCP COPS RSVP name, password secret You can do this or you can’t COPS= Common Open Policy Service protocol RAP WG = Resource Allocation Protocol

41. 41oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Typical Use for ERP/Mission Critical 1: Application signals “identity” and no bandwidth (“Null Service”) 2: Router relays identity to Policy Server via COPS 3: PS returns DSCP to be used for this application 4: Network edge Device programmed to allow this DSCP on this port 5: Host notified of which DSCP to use via DCLASS in Resv handset PBX server Server Diff-Serv (*) concept formerly introduced as “RSVP+” Path Resv 1 Policy Server 2 3 5 4

42. 42oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Diff-Serv Acceptance Time Enthusiasm today Diff-Serv will solve some of the world’s QoS Diff-Serv Engineering? Diff-Serv SLA ? Internet e2e SLA? Diff-Serv Routers Diff-Serv Design & Deployment intra Domain (eg VPN QoS) Real value Inter-SP Diff-Serv and end-to-end Internet QoS need further standardisation and commercial arrangements

43. 43oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Int-Serv/RSVP Acceptance Time Enthusiasm Today Intra-ISP Int-Serv/RSVP will solve the world’s QoS ISP mapping RSVP over ATM Real value Today Enterprise for VoIP in Enterprise for Mission Critical and Multimedia in Enterprise (Int-Serv over Diff-Serv) for MPLS TE in ISP Cool thing to say: “RSVP does not scale”

44. 44oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com What Are 802.1P and ISL? QoS for a Layer 2 Ethernet switched world! 802.1P QoS is: An IEEE specification Focuses on support for QoS over LANs and 802.1Q trunks Supports 8 classes of service ISL QoS is: Cisco specification Focuses on support for QoS over ISL trunks Supports 8 classes of service

45. 45oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com Differences Between 802.1P and ISL ISL Header 26 Bytes Encapsulated Frame 1 to 24.5 KBytes FCS 4 Bytes PTDATAFCSPREAM.SFDDASA Layer 2 802.1Q/p TAG 4 Bytes 3 bits used for CoS (user priority) Layer 2 ISL 3 bits used for CoS

46. 46oebb_update_062k © 1999, Cisco Systems, Inc. www.cisco.com How 802.1p QoS Functions Edge QoS based on 802.1P CoS: Mark 802.1p Priority bits on untagged packets on per port basis Do you trust the device on the port to set the bits correctly? Upstream Layer 3 device performs TOS mapping to map 802.1P to IP Precedence or DSCP

47. 47 Presentation_ID © 1999, Cisco Systems, Inc. www.cisco.com