Technology - IP Techniques 7 - Quality of Service

Synopsis

Quality of Service (QoS) is the ability to reserve capacity on a network so it will deliver a specified rate of packets within guaranteed delay, jitter and packet loss constraints. QoS is vital for video, VoIP and many other applications. This report discusses QoS techniques including explicit congestion notification, IntServ and DiffServ for IPv4, IPv6 and MPLS streams and the use of the EXP bits in the MPLS header.

Table of Contents

• 1. Synopsis
• 2. Introduction
  • 2.1 Reservation and guaranteed QoS – IntServ
  • 2.2 Prioritisation without guarantees – DiffServ and Class of Service
  • 2.3 IP not designed for QoS
  • 2.4 Asynchronous Transfer Mode (ATM)
• 3. Methods of applying QoS to IP
  • 3.1 QoS attributes
    • 3.1.1 Data rate and dropped packets
    • 3.1.2 Delay and Jitter
    • 3.1.3 Out of order delivery
    • 3.1.4 Errors in packet payloads
  • 3.2 IntServ – guaranteed QoS
    • 3.2.1 Resource Reservation Protocol (RSVP) – with IP
    • 3.2.2 RSVP-TE - with MPLS
  • 3.3 DiffServ and Class of Service (CoS)
    • 3.3.1 Per-Hop Behaviour (PHB)
    • 3.3.2 IPv4 DiffServ field
    • 3.3.3 IPv6 DiffServ field
    • 3.3.4 DiffServ Code Point basic values and PHBs
    • 3.3.5 Assured Forwarding PHBs
    • 3.3.6 Expedited Forwarding PHB
    • 3.3.7 Metering and marking
• 4. MPLS with DiffServ
  • 4.1 MPLS’s EXP bits
    • 4.1.1 Ordered aggregate
    • 4.1.2 Drop precedence
  • 4.2 EXP-Inferred-PSC (E-LSP)
  • 4.3 Label-Only-Inferred-PSC (L-LSP)
  • 4.4 Mapping IP DiffServ to EXP bits
• 5. Ethernet VLAN QoS
• 6. WiFi 802.11e QoS
• 7. Explicit Congestion Notification
• 8. Related reports