Cisco 6500 - Catalyst Series 10 Gigabit EN Interface Module Expansion White Paper - Page 2

Browse online or download pdf White Paper for Switch Cisco 6500 - Catalyst Series 10 Gigabit EN Interface Module Expansion. Cisco 6500 - Catalyst Series 10 Gigabit EN Interface Module Expansion 18 pages. Distributed forwarding card 4 for ws-x68xx, ws-x69xx, and select ws-x67xx modules
Also for Cisco 6500 - Catalyst Series 10 Gigabit EN Interface Module Expansion: Installation Note (14 pages), Solution Manual (17 pages), Installation Note (46 pages), White Paper (19 pages), Description (1 pages), Product Bulletin (6 pages), Notice (4 pages), Datasheet (9 pages), Datasheet (18 pages), Configuration Manual (8 pages), Installation Note (28 pages), Troubleshooting Manual (11 pages), Installation Note (18 pages), User Manual (17 pages), Installation Note (24 pages), Manual (19 pages), Installation Note (36 pages)

Print Page
Cisco 6500 - Catalyst Series 10 Gigabit EN Interface Module Expansion White Paper
Figure 1. CoS Field
®
Cisco Systems
supports the Inter-Switch Link (ISL) VLAN tagging option on selected Cisco Catalyst 6500 line cards. ISL is a Cisco proprietary
VLAN tagging option that also supports an inbuilt 3-bit CoS field just like the IEEE 802.1Q option mentioned earlier.
Type of Service
Built into every IP packet is an IP header, and like in the Ethernet example earlier, the IP header also contains a field that defines a priority value
for this packet. This field is the type-of-service (ToS) field. Unlike the CoS field, the ToS field is an 8-bit field. There are two ways to set a priority
value in the ToS field. One method, called IP precedence, uses the 3 most significant bits of the ToS field to yield eight priority values.
Differentiated Services Code Point (DSCP) is a second method for assigning a priority to an IP packet. DSCP uses the 6 most significant bits of the
ToS field to yield 64 different priority values. Figure 2 shows where the ToS bits are found in the IP header.
Figure 2. Reading IP Precedence and DSCP from the ToS Byte
© 2005 Cisco Systems, Inc. All rights reserved.
Important notices, privacy statements, and trademarks of Cisco Systems, Inc. can be found on cisco.com.
Page 2 of 18