Foundation Summary
This section is a collection of information that provides a convenient review of many key concepts in this chapter. If you are already comfortable with the topics in this chapter, this summary can help you recall a few details. If you just read this chapter, this review should help solidify some key facts. If you are doing your final preparation before the exam, these tables are a convenient way to review the day before the exam.
Table 15-5 summarizes the various advanced queuing techniques discussed in this chapter.
Table 15-5 Queuing Summary
|
FIFO |
Class-Based Weighted Fair |
Low-Latency |
|
No configuration |
Define flows (class-map), policy per flow (policy-map), and assign to an interface (service-policy) |
Same configuration as CBWFQ, but add a priority queue for delay-sensitive traffic |
|
No priority traffic |
Administrator-defined policies |
High-priority traffic has its own priority queue—guarantee of service |
|
Traffic dispatched on first-come, first-served basis |
Traffic dispatched using WFQ between flows, FIFO within flows |
Priority queue is sent first, then remaining queues are WFQ, with FIFO within a queue |
Table 15-6 summarizes the various queuing commands discussed in this chapter.
Table 15-6 Queuing Command Summary
|
Command |
Function |
|
class-map { match-all | match-any } class-map-name |
Creates a data structure to select specific traffic. match-all is an AND of all conditions within the class-map. match-any is an OR of the conditions within the class-map. |
|
match |
Matches specific traffic within a class-map (defined below). |
|
access-group {number | name} |
Matches a numbered or named IP access list. |
|
any |
Matches all traffic. |
|
class-map class-map-name |
Creates a nested class-map. |
|
cos IP-TOS |
Matches the IP ToS bits. |
|
destination-address mac MAC-address |
Matches a specific destination MAC address. |
|
input-interface interface |
Matches the interface the traffic arrived on. |
|
ip {dscp value | precedence value | rtp start-port port-range} |
Matches various IP header values. |
|
mpls experimental value |
Matches the MPLS experimental bits. |
|
protocol value |
Matches any given protocol. |
|
qos-group value |
Matches traffic from a specific QoS group. |
|
source-address mac MAC-address |
Matches a specific source MAC address. |
|
policy-map policy-map-name |
Creates a data structure to reference one or more class-maps and is assigned to an interface. |
|
class class-map-name |
Maps the class-map (defined earlier) to the policy-map. There are many parameters (below) to reference only specific traffic within the class map. |
|
bandwidth {Kbps-value | percent value} |
Defines how traffic is handled during congested situation (CBWFQ). |
|
priority Kbps-value |
Defines how traffic is handled at all times (LLQ). |
|
queue-limit #-packets |
Defines how many packets may reside in a particular queue. |
|
service-policy policy-map-name |
Creates nested policy maps. |
|
shape {average bps-value | max-buffers buffer-value | peak bps-value} |
Defines traffic shaping (buffering) parameters. |
|
police bps-value |
Defines traffic policing (discarding) parameters. |
|
set {cos value | ip value | mpls experimental value | qos-group value} |
Allows marking of various parameters. |
|
service-policy { input | output } policy-map-name |
Assigns a policy map to an interface. Packet queuing is normally done outbound. |
Table 15-7 summarizes the various advanced queuing techniques discussed in this chapter.
Table 15-7 Compression Summary
|
Link |
Stac |
Predictor |
Payload |
TCP Header |
|
Compresses OSI Layers 2–7 |
Very CPU intensive |
Memory intensive |
Compresses OSI Layers 3–7 |
Compresses OSI Layers 3–4 |
|
Two algorithms = Stac and Predictor |
Replaces redundant strings with tokens |
Replaces text with smaller codes |
|
Compresses ONLY IP and TCP headers |
|
|
Does not expand encrypted or compressed data (no redundant strings) |
Could possibly expand compressed data |
|
Good for very small data packets |
|
|
Open standard |
Cisco proprietary |
Open standard |
|
|
Used across point-to-point circuits only |
Can be used on both PPP and HDLC links |
Can be used on PPP links only |
Can be used on HDLC, PPP, and Frame Relay links |
Can be used on any links |