Quality of ServiceCLASSIFICATION AND MARKING

What is QoS?1. It’s a CCIE topic – but that doesn’t mean you can’t learn!

1. Understand traffic flows

A B

SYNSYN, ACK

ACK

ESTABLISHED

A BTCP UDP

SRC & DST IPs and Ports

Hardware Queue

Categories of QoS1. Classification and Marking

2. Congestion Management and Avoidance

Packet (EF)Packet

(AF21)Data Packet

(EF)Voice Packet

Soft Priority Queue

Soft Queue

Hardware Queue

Categories of QoS1. Classification and Marking

2. Congestion Management and Avoidance

3. Shaping, Policing, and Link Fragmentation1. Rate limiting

1. Shaping buffers offending packets while policing is a little more rough and by default drops offending packets.

Packet (EF)Packet

(AF21)Data Packet

(EF)Voice Packet

QoS Fields1. IP ToS Byte

2. CoS (802.1q and ISL)

3. WAN

QoS Fields1. IP ToS Byte

QoS Fields1. CoS and WAN fields

1. CoS has 3 bits to work with on the 802.1q header and ISL header2. WAN markings aren’t’ much

1. MPLS has 3 bits to work with, Frame-Relay and ATM both have 1 bit1. IP header maintains it’s markings, but not much good over L2 and L2.5 WAN networks

QoS Fields Continued…Field Location Length

IP Precedence (IPP) IP Header 3 bits

IP DSCP IP Header 6 bits

DS Field IP Header 1 byte

ToS Byte IP Header 1 byte

CoS ISL and 802.1q header 3 bits

Discard Eligible (DE) Frame Relay header 1 bit

Cell Loss Priority (CLP) ATM cell header 1 bit

MPLS Experimental MPLS header 3 bits

Per Hop Behaviors (PHB)DSCP Class Selector Names

Binary DSCP Values IPP Binary Values IPP Names

Default/CS0* 000000 000 Routine

CS1 001000 001 Priority

CS2 010000 010 Immediate

CS3 011000 011 Flash

CS4 100000 100 Flash Override

CS5 101000 101 Critical

CS6 110000 110 Internetwork Control

CS7 111000 111 Network Control

Assured Forwarding PHB and DSCP Values

Queue Class

Low Drop Probability Medium Drop Probability High Drop Probability

Name/Decimal/Binary Name/Decimal/Binary Name/Decimal/Binary

1 AF11 / 10 / 001010 AF12 / 12 / 001100 AF13 / 14 / 001110

2 AF21 / 18 / 010010 AF22 / 20 / 010100 AF23 / 22 / 010110

3 AF31 / 26 / 011010 AF32 / 28 / 011100 AF33 / 30 / 011110

4 AF41 / 34 / 100010 AF42 / 36 / 100100 AF43 / 38 / 100110

Expedited Forwarding PHB and DSCP Values1. Two PHBs

1. Quick scheduling low latency queuing2. Police to ensure EF packets do not hog all the bandwidth and/or starve

the other queues.3. Decimal 46 – Binary 101110

1. AF11 / 10 / 0010101. AF1 | 1 = 001 | 01 | 0

1. 001010 = 10

2. AF43 / 38 / 1001101. AF4 | 3 = 100 | 11 | 0

1. 100110 = 38

Assured Forwarding PHB and DSCP Values Continued…

Modular Quality of Service CLI1. Class map

1. Used to Classify your traffic

2. Policy Map1. Used to Mark your traffic (and choose what to do with marked traffic) this is also where you set

Congestion Management and Policing. Normally we want to keep marking as close to the source as possible, but best practices aren’t always possible…

3. Service Policy1. Same thing as a policy-map, but you use the service-policy command on an interface to apply the

policy map

Network Based Application Recognition (NBAR)

1. NBAR is also known as Deep Packet Inspection

2. NBAR has the ability to look past TCP and UDP ports such as the URL, MIME type in HTTP requests allowing recognition of application information

3. Ability to use regular expressions to isolate the domain or another portion

4. Use the match protocol command under a class map to use NBAR to match traffic