HP 2424M - Manual (Page 16)

HP ProCurve Switch 4000M / 8000M / 2424M / 1600M Reviewer’s Guide
• Source or destination IP address (up to 30 different addresses)
• IP-ToS or Diff-Serv field – Based on the IP Type of Service or Diff-Serv field
• Protocol type of the packet – Priority set based on whether packet is IP, IPX, ARP, DEC LAT,
AppleTalk, SNA or NetBeui
• VLAN membership
• Incoming 802.1p Priority setting
If a packet meets more than one of the conditions above, the priority setting of the packet is
determined in the order given above, with the first in the list having the highest precedent.
These settings determine not only the priority of how the packet is handled in the HP ProCurve
Switch 4000M/8000M/2424M/1600M itself, but the switch will also set the 802.1p priority tag for the
packet outbound from the switch if it leaves via an 802.1p tagged port. This feature can be used to
provide a network end-to-end priority for a packet. The HP ProCurve 9300 Routing Switches, for
example, will internally maintain and prioritize the packet based on this 802.1p tag, even when the
packet is routed through the 9300 Routing Switch.
End-to-end priority setting is thus possible even
without the end node that created the packet explicitly
setting the priority in the packet. This is advantageous in that end node NIC cards do not have to be
replaced or have their drivers updated in order to take advantage of priority settings. The end user also
doesn’t have to wait for PC operating systems and applications to support priority settings. The Switch
4000M/8000M/2424M/1600M provides 802.1p edge or backbone services for end nodes into the rest of
the network, a powerful capability as different data types converge in the data network.
In addition, this feature can be used to reset the incoming 802.1p priority setting, thus allowing the
network manager an override capability from errant end nodes once they do support 802.1p priority
settings.
2.7.3 IP-ToS Support
The IP-ToS (Type of Service) field has been in the IP header for a long time, but until recently has been
largely unused. There are a number of applications now starting to use this field, such as IP-telephony,
to provide priority handling of such packets within a network. Since many emerging switches use the
802.1p field to provide priority rather than the IP-ToS field, the HP ProCurve
Switch 4000M/8000M/2424M/1600M’s ability to map this field to an 802.1p priority setting provides more
flexibility in a network as to how this packet will be handled end-to-end.
2.7.4 Diff-Serv Support
An upcoming standard, Differential Services (Diff-Serv) will use the IP-ToS field to provide a
standardized set of class-of-service for packets. Still in the standards definition phase, Diff-Serv will be
used in the future to define a full set of delivery services for a packet. The HP ProCurve
Switch 4000M/8000M/2424M/1600M can be configured to specify a particular 802.1p priority setting and
set the 802.1p tag for each of the 32 different settings that the Diff-Serv field can take. This provides
future proofing for a network using the HP ProCurve Switch 4000M/8000M/2424M/1600M.
2.8 IGMP Support
For multicast traffic, the switch eavesdrops on Internet Group Multicast Protocol (IGMP) traffic so that
it knows which nodes are part of which multicast groups. If there is no multicast router available, the
HP ProCurve Switch 4000M/8000M/2424M/1600M can act as an IGMP querier to learn which nodes have
subscribed to which multicast streams. The switch can then direct a specific multicast stream to only
those switch segments that have nodes that have joined the multicast group associated with that
stream. Configuration of this feature is a single check box to turn it on. HP switches support version 2
of IGMP.
©1998, 1999, 2000 Hewlett-Packard Co Revision 3.2b – 1/15/2000 Page 16 of 36