1 / 10

L2 QoS Technologies

L2 QoS Technologies. CIT 443. LAN Based QoS. LANs create significant difficulty in implementing QoS Shared bandwidth

lada
Download Presentation

L2 QoS Technologies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. L2 QoS Technologies CIT 443

  2. LAN Based QoS • LANs create significant difficulty in implementing QoS • Shared bandwidth • In a hierarchical layer two switched environment (especially a VLAN environment) there are no means of reading DiffServe CodePoints (they’re in the layer three header) or of reserving bandwidth via RSVP (there is no router present)

  3. LAN Based QoS – 802.1p • Switched LANs use a different prioritization standard known as IEEE 802.1p • 802.1p provides up to eight priority levels in a special field in the frame header called the 802.1p tag • 802.1p priority levels are marked on the NIC • The NIC must support 802.1p tagging • The OS must tell the NIC the priority to put into the 802.1p tag based on input from the source application

  4. LAN Based QoS – 802.1p • Normal values • Guaranteed service • Controlled load • Qualitative • Applications that need specific bandwidth must be “QoS aware” • They speak to the OS’s protocol stack through the generic QoS API (GQoS API) • Available since Win98SE • If no tag is presented then the traffic is considered “best available” • All bandwidth remaining after prioritized traffic is processed is given to this traffic type

  5. LAN Based QoS – 802.1p • 802.1p only prioritizes frames across the network segment • Layer two switches prioritize the traffic based on the tags • The prioritization information is removed at the next hop (layer three processing device – host or router) • Traffic prioritization levels are set by the network segment’s Subnet Bandwidth Manger (SBM) • The SBM broadcasts it’s presence so that everyone knows to re-route the RESV requests • The SBM determines the rules for the flow and sends a prioritization level to be used in the tag to the source • SBMs can be implemented in hosts, switches, or routers

  6. LAN Based QoS – 802.1p • Integration with RSVP • RESV requests from the source are re-routed to the SBM rather than the next router • The SBM assigns priority for the flow across the network segment • The SBM forwards the RESV request to the next upstream router or destination

  7. LAN Based QoS – MPLS • Used to support layer two QoS across multiple layer two technologies • ATM • Frame Relay • Ethernet • Token Ring • Basically creates a connection across a connectionless network • Removes the requirement for each switch or router to make an independent prioritization decision • The connections are known as Label Switch Paths or LSPs

  8. LAN Based QoS – MPLS • Process • Label Edge Routers (LER) examine the packet and encapsulate it with an MPLS header for the next hop that contains the LSP for the packet • MPLS headers are available for each layer two technology • MPLS header is a “shim” between L2 and L3 headers • The LSR then forwards the packet to the next routers (known as Label Switch Routers) • Each router pulls the LSP from the MPLS header and places it into a new MPLS header for the next hop • Each label has only local significance to the LSR

  9. LAN Based QoS – MPLS • Process (cont.) • Routers share MPLS label information using the Label Distribution Protocol (LDP) • Relies in the underlying routing protocol to distribute networks for paths • For public MPLS, LDP relies on BGP

  10. Other L2 QoS Standards?

More Related