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Ethernet Basics – 6

Ethernet Basics – 6. Quality of Service/Class of Service (QOS/COS). Quality of Service/Class of Service (QOS/COS). The problem- You have multiple traffic streams using the same ports, but some are more important than others Solution- Implement QOS/COS What is the difference?

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Ethernet Basics – 6

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  1. Ethernet Basics – 6 Quality of Service/Class of Service (QOS/COS)

  2. Quality of Service/Class of Service (QOS/COS) • The problem- You have multiple traffic streams using the same ports, but some are more important than others • Solution- Implement QOS/COS • What is the difference? • QOS- the level of guarantee that I have that a given packet of some importance will make it to the end point • COS- The way you can classify a given traffic type so that QOS can take place • There are 3 ways to provide Class of Service- • Port based Prority (802.1p)- network centric • TOS- A field in the IP packet header. The contents of this byte specify the kind of transmission desired, with respect to delay, throughput and reliability- generated by the end device, handled by the network

  3. Quality of Service/Class of Service (QOS/COS) • Differentiated Service (DIFFSERV)- A replacement header field, called the DS field, is defined, which is intended to supersede the existing definitions of the IPv4 TOS octet [RFC791] and the IPv6 Traffic Class octet [IPv6]. Six bits of the DS field are used as a codepoint (DSCP) to select the per-hop-behavior a packet experiences at each node. This is both end user and network based mechanism • Ethernet Direct currently supports Port Based 802.1p • 802.1p is also the easiest to implement • 802.1p has 2 classes of priority- normal and high • 0-3 Normal • 4-7 High

  4. Preamble SFD Destination- Address Source Address Length/Type Data FCS Preamble SFD Destination- Address Source Address TAG Length/Type Data FCS Prioritisation (QoS) • Original Ethernet standards • Maximum frame size – 1518 bytes • Recent change to allow Prioritisation • Maximum frame size – 1522 bytes (increase of 4 bytes) 64 byte - 1518 byte TPID = Tag Protocol Identifier TCI = Tag Control Information CFI = Canonical Format Indicator TPID TCI User Priority Tag Protocol ID CFI VLAN ID 16 bit 3 bit 1 bit 12 bit

  5. Video Voice Prioritisation (QoS) Email + Attach File Priority Voice 6 Video 5 File 3 Email 0

  6. Thank You If you have any questions or comments about this presentation, email us at techsupport@ethernetdirect.com Or Skype us at Ethernet Direct1

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