L3 QoS Standards

1
L3 QoS Standards

• CIT 443

2
Differentiated Services

• DiffServ
• IETF Standard
• RFC 2474 2475

3
DiffServ

• Priority is set in DS CodePoint (DSCP) byte of
  the IP Header
• IPv4 Type of Service field
• IPv6 Traffic Class field
• 8 bits hence the DSCP byte
• Two bits are reserved
• Six bits (64 values) are used for priority levels
• 32 are reserved for testing

4
(No Transcript)
5
DiffServ
Image from Cisco Systems Inc http//www.cisco.com
/en/US/technologies/tk543/tk766/technologies_white
_paper09186a00800a3e2f.html
6
DiffServ
Image from Cisco Systems Inc http//www.cisco.com
/en/US/technologies/tk543/tk766/technologies_white
_paper09186a00800a3e2f.html
7
(No Transcript)
8
DiffServ

• Each network device
• Must support DiffServ
• Must agree on the treatment for each CodePoint
  value (policy)
• Queues and forwards based on ToS priority

9
DiffServ

• Per hop forwarding policies
• Expedited Forwarding (EF) RFC 3246
• Maximum priority
• Packets matching the EF CodePoint are immediately
  forwarded
• Egress rate exceeds the ingress rate on these
  packets
• Must be kept to a small fraction of overall
  traffic
• Assured Forwarding (AF)
• Four priorities
• Gold, Silver, Bronze, Best Available

10
DiffServ

• Limitations
• Requires advance provisioning and bandwidth
  reservation
• All network devices must agree on the
  prioritization scheme
• Including the source, destination, and all
  intermediate networks

11
For Next Time

• Find and document the table of all DiffServ Code
  Points (DSCP)
• Identify which DSCP values would be applicable to
  the service(s) you are deploying in lab
• Be sure to include all necessary references