We continue with a detailed study of Microsoft Azure stack as inferred from an introduction of Azure by Microsoft. We reviewed some more features of Azure networking.  We discussed global DNS, dual stacks for IPV4 and IPV6, and load balancers.
Azure load balancer services come at different levels. There is the traffic manager for cross region direction and availability and exposure to the internet.  There is the Azure Load Balancer which provides in-region scalability and availability. There is the Azure application gateway which has URL/content based routing and load balancing. Then there is load balancing on the VMs for web servers.
Load Balancers in Azure use multiple VIPs to simplify designs and reduce cost. They can be setup with internal and external VIP with direct public association. 
Application Gateway can manage backend with rich diagnostics including access and performance logs, VM scale set support and custom health probes.
The Web Application Firewall security protects applications from web based intrusions and is built using ModSecurity and CoreRule set. It is highly available and fully managed.
Cross premises connectivity is maintained with P2S SSTP tunnels and IPSEC S2S VPN tunnels to Azure over Internet. If there is a private WAN, an ExpressRoute is maintained to Azure.
There is dual redundancy with Active-Active gateways which is new in Microsoft Azure. This leads to zero downtime during planned maintenance. This is an improvement from active-standby to active-active. It supports both cross-premises and VNet to VNet connectivity and spreads traffic over multiple tunnels simultaneously. 
There are thirty five express route locations in Microsoft Azure which is more than any other cloud. This has nearly doubled peering locations and partners. There are also improvements in ExpressRoute It supports upto 10G throughputs to VNets where usually the standard is 1Gbps and the high performance is 2Gbps. It has the best cloud enterprise connectivity SLA. It offers more insights, self-help and troubleshooting tools, improved monitoring, diagnostics and alerting than others. We can also see BGP routes, traffic statistics, and ARP tables.
Microsoft Azure has deeper insights into our network regardless of whether it is ExpressRoute, VirtualNetwork or ApplicationGateway For example, the Express Route has peering connection statistics, ARP table, route summary, and route table. The Virtual network has effective security rules on every NIC, and next hop and effective routes for every NIC in the subnet. The Application Gateway has metrics and alerts and back end health information.
#codingexercise
Find pairs with given sums such that pair elements lie in different BSTs.
void GetPairSum(Node root1, Node root2, int sum)
{
var list1 = root1.ToInOrder();
var list2 = root2.ToInOrder();
int left = 0;
int right = list2.Count-1;
while ( left < list1.Count && right >= 0)
{
 if (list1[left] + list2[right] == sum)
{
    Console.WriteLine("{0}:{1}", list1[left], list2[right]);
    left++;
    right--;
}else if ( list1[left] + list2[right] < sum )
{
    left++;
}else
    right--;
}
}
It might be noted that this does not take care of duplicates.