Explanation
+ bandwidth management technique which delays datagrams: shaping+ mechanism to create a scheduler for packets prior to forwarding: policy map+ portion of the IP header used to classify packets: DSCP+ mechanism to apply a QoS policy to an interface: service policy+ tool to enforce rate-limiting on ingress/egress: policing+ portion of the 802.1Q header used to classify packets: CoS To attach a policy map to an input interface, a virtual circuit (VC), an output interface, or a VC that will be used as the service policy for the interface or VC, use the service-policy command in the appropriate configuration mode.
Class of Service (CoS) is a 3 bit field within an Ethernet frame header when we use 802.1q which supports virtual LANs on an Ethernet network. This field specifies a priority value which is between 0 and 63 inclusive which can be used in the Quality of Service (QoS) to differentiate traffic.
The Differentiated Services Code Point (DSCP) is a 6-bit field in the IP header for the classification of packets. Differentiated Services is a technique which is used to classify and manage network traffic and it helps to provide QoS for modern Internet networks. It can provide services to all kinds of networks.
Traffic policing is also known as rate limiting as it propagates bursts. When the traffic rate reaches the configured maximum rate (or committed information rate), excess traffic is dropped (or remarked). The result is an output rate that appears as a saw-tooth with crests and troughs.
Traffic shaping retains excess packets in a queue and then schedules the excess for later transmission over increments of time -> It causes delay.

172.16.50.5 in hex is
We will have the answer from this paragraph:
"TLV values for the Option 43 suboption: Type + Length + Value. Type is always the suboption code 0xf1. Length is the number of controller management IP addresses times 4 in hex. Value is the IP address of the controller listed sequentially in hex. For example, suppose there are two controllers with management interface IP addresses, 192.168.10.5 and 192.168.10.20. The type is 0xf1. The length is 2 * 4 = 8 = 0x08. The IP addresses translates to c0a80a05 (192.168.10.5) and c0a80a14 (192.168.10.20). When the string is assembled, it yields f108c0a80a05c0a80a14. The Cisco IOS command that is added to the DHCP scope is option 43 hex f108c0a80a05c0a80a14." Reference:
Therefore in this question the option 43 in hex should be "F104.AC10.3205 (the management IP address of 172.16.50.5 in hex is AC.10.32.05).

Explanation
Timeout (in milliseconds) sets the amount of time an IP SLAs operation waits for a response from its request packet. In other words, the timeout specifies how long the router should wait for a response to its ping before it is considered failed.Threshold (in milliseconds too) sets the upper threshold value for calculating network monitoring statistics created by an IP SLAs operation. Threshold is used to activate a response to IP SLA violation, e.g. send SNMP trap or start secondary SLA operation. In other words, the threshold value is only used to indicate over threshold events, which do not affect reachability but may be used to evaluate the proper settings for the timeout command.
For reachability tracking, if the return code is OK or OverThreshold, reachability is up; if not OK, reachability is down.
This
tutorial can help you revise IP SLA tracking topic:
http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/813-cisco-router-ipsla-basic.html and
http://www.ciscozine.com/using-ip-sla-to-change-routing/
Note: Maybe some of us will wonder why there are these two commands:
R1(config)#ip route 0.0.0.0 0.0.0.0 172.20.20.2 track 10 R1(config)#no ip route 0.0.0.0 0.0.0.0 172.20.20.2 In fact the two commands:
ip route 0.0.0.0 0.0.0.0 172.20.20.2 track 10 ip route 0.0.0.0 0.0.0.0 172.20.20.2 are different. These two static routes can co-exist in the routing table. Therefore if the tracking goes down, the first command will be removed but the second one still exists and the backup path is not preferred. So we have to remove the second one.

Explanation