UDP does not do any of these services, and instead requires higher layer protocols to handle them. When talking about port numbers, you must indicate if the port number is TCP or UDP, especially when asking firewall teams to open ports. Most of the common ports are TCP, but some e. Voice are UDP. Higher layer protocols run on top of lower layer protocols.
Different port numbers on either side means different TCP Connections. You can view these TCP Connections by running netstat on the server. This means firewall administrators do not have to explicitly permit reply traffic since the firewall will do it automatically. Use Telnet to verify that a Service is listening on a TCP Port number — when you telnet to a server machine on a particular port number, you are essentially completing the three-way TCP handshake with a particular Server Service.
If packets arrive out of order, UDP cannot determine this, and cannot reassemble them in the correct order. No acknowledgements — When UDP packets are received, the receiver does not send an acknowledgement back to the sender. The smaller header size and the lack of three-way handshake means UDP is a lightweight protocol that performs better on high latency and low bandwidth links. Each URL can be broken up into three sections:.
Why forward slashes in URLs? Different codes mean success or error. Code means success. Machines on the subnet can communicate directly with other machines on the same subnet. When one machine puts electrical signals on the wire, every other machine on the same wire sees the electrical signals.
A network packet or frame is a collection of electrical signals. Routers — If two machines are on different subnets, then those two machines can only communicate with each other through an intermediary device that is connected to both subnets.
This intermediary device is called a router. The router is connected to both subnets wires and can take packets from one subnet and put them on the other subnet. Layer 2 — When machines on the same subnet want to communicate with each other, they use a Layer 2 protocol, like Ethernet. Layer 3 — When machines on different subnets want to communicate with each other, they use a Layer 3 protocol, like IP Internet Protocol. Destination is either local or remote — since different protocols are used for intra-subnet Layer 2 and inter-subnet Layer 3 , the machines need to know which machines on are on the local subnet, and which machines are on a remote subnet.
All machines are also configured with a subnet mask. If two machines have the same subnet ID, then those two machines are on the same subnet. If two machines have different subnet IDs, then those two machines are on different subnets. Every machine sees every packet — A characteristic of Layer 2 Ethernet is that every machine sees electrical signals from every other machine on the same subnet.
MAC addresses — When two machines on the same subnet talk to each other, they use a Layer 2 address. In Ethernet, this is called the MAC address. All machines on the same subnet see the packet.
Source MAC address — When an Ethernet packet reaches a destination machine, the destination machine needs to know where to send back the reply. If the destination IP address is on the same subnet as the source machine, then the destination IP address must first be converted to a Layer 2 MAC address. Every machine on the same subnet sees the message. If one of the machines is configured with IP address IP Conflict — a particular IP address can only be assigned to one machine.
Since only half the packets are reaching each machine, both machines will stop working. Routing to other subnets — When a machine wants to talk to a machine on a different subnet, the source machine needs to send the packet to a router. The router will then forward the packet to the destination machine on the other subnet. Default gateway — Every client machine is configured with a default gateway , which is the IP address of a router on the same subnet as the client machine.
The client machine assumes that the default gateway router can reach every other subnet. The router has a list of which IP subnet is on which router interface. If the router is not directly connected to the subnet that contains the destination IP address, then the router will probably send the packet to another router for additional routing.
The Router makes a couple changes to the packet before it puts the modified packet on the destination interface. Here are the modifications:. Router-to-router communication — When a router receives a packet that is destined to a remote IP subnet, the router might not be Layer 2 Ethernet connected to the destination IP subnet.
In that case, the router needs to send the packet to another router. Both routers need to be connected to the same Ethernet subnet. Routing Protocols — Routers communicate with each other to build a topology of the shortest path or quickest path to reach a destination IP subnet. Switch backplane — Today, each machine connects a cable to a port on a switch.
The switch merges the switch ports into a shared backplane. Switches switch known MAC addresses to only known switch ports — If the switch knows which switch port connects to the destination MAC address of an Ethernet packet, then the switch only puts the Ethernet packet on the one switch port. This means that Ethernet packets are no longer seen by every machine on the wire. This improves security because NIC promiscuous mode no longer sees every packet on the Ethernet subnet.
If one of the switch ports replies, then the switch learns the MAC address on that switch port. Switches flood broadcast packets — The switch also floods Ethernet broadcast packets to every switch port in the Ethernet subnet.
Some Switches can route — Some Switches have routing functionality Layer 3. DNS converts words to numbers — When users use a browser to visit a website, the user enters a human-readable, word-based address. The client machine then connects to the IP Address. To handle this scalability problem, DNS names are split into a hierarchy, with different DNS servers handling different portions of the hierarchy.
For example, www. DNS is not in the data path. The same companies that provide public website hosting also provide public DNS zone hosting. Internal clients resolving FQDNs to internal IP addresses avoids internal clients needing to go through a firewall to reach the servers.
Cable Bonding — Two or more cables can be bound together to look like one cable. This increases bandwidth, and increases reliability. If you bond 4 Gigabit cables together, you get 4 Gigabit of bandwidth instead of just 1 Gigabit of bandwidth. If one of those cables stops working for any reason, then traffic can still use the other 3 cables.
Cable Bonding does not impact network functionality — Cable bonding does not affect networking in any way. Bond Both Sides — to bond cables together, you must configure both sides of the connection identically.
You configure the switch to bond cables. And you configure the ADC or server to bond cables. To get around this problem, when a port channel bond is configured, a single MAC address is shared by all of the cables in the bond, and both sides of the cable bond know that the single MAC address is reachable on all members of the cable bond.
Load Balancing across the bond members — The Ethernet switch and the ADC will essentially load balance traffic across all members of the bond. There are several port channel load balancing algorithms. But the most common algorithm is based on source IP and destination IP; all packets that match the same source IP and destination IP will go down the same cable.
Packets with other combinations of source IP and destination IP might go down a different cable. LACP — Cables can be bonded together manually, or automatically. Multi-chassis refers to multiple switches. You almost always want multi-chassis since that lets your Port Channel survive a switch failure.
Port Channel Configuration — first, ask the switch administrator to create a port channel using multiple switch ports. Each switch port is configured to belong to a particular VLAN. Ports in separate VLANs use routers to communicate with each other.
Switch ports default as Access Ports unless a switch administrator specifically configures it as a Trunk Port. Trunk Ports reduce the number of cables — if you had to connect a different cable or Port Channel from ADC for each VLAN, then the number of cables and switch ports can quickly get out of hand.
The purpose of Trunk Ports is to reduce the number of cables. Trunk Ports and Port Channels are separate features — If you want to bond multiple cables together, then you configure a Port Channel.
These are two completely separate features. Port Channels can be Access Ports. Routing is configured in a separate part of the Layer 3 switch, or on a separate router device. In other words, Trunk Ports are unrelated to routing.
A single machine e. Port Channels require identical configuration on the switch side and on the ADC side. One Default Route — the routing table usually has a route 0. There can only be one default route on a device even if that device is connected to multiple VLANs.. ADC-owned IP addresses cannot be configured on any other networking device.
When you create a Virtual Server e. When ADC appliances need to send a packet, they look in the routing table for the next hop address and select a SNIP on the same subnet as the next hop. Web servers reply to the SNIP. The web server does not see the original Client IP address. This behavior is sometimes called Source NAT. ADC has at least three tables for choosing how to forward route a packet. They are listed below in priority order. ADC networking is configured completely differently than server networking.
ADC is configured like a switch, not like a server. One subnet for everything? The switch port should be an access port for the management VLAN. The remaining interface in VLAN 1 is your management interface. Link Redundancy — for each VLAN, connect at least two cables, preferably to different switches, and then bond the cables together into a port channel. If not, then layer 2 is not configured correctly somewhere e. Layer 3 Troubleshooting — There are many potential causes of Layer 3 routing issues.
Then work with the firewall and routing teams to troubleshoot packet routing. The two appliances must be identical hardware, identical firmware version, and identical licensed edition. HA heartbeat packets are untagged — Each node in a HA pair sends heartbeat packets out all interfaces.
How do you upgrade license keys in my VMware? How do you downgrade license keys in MyVMware? How do I access my license keys? My support has expired what do I do? What is the warning period? Are there any options to continue supporting those products that are no longer available in the Standard Bundle 5pt? A La Carte. Which is the next lowest bundle in the program? Will there be a replacement package VMware can highlight? What are the usage meter reporting implications of this change?
What are the benefits of transitioning to another bundle? Who does it impact? How VCloud Air Network addresses new markets? How does VCloud Air Network benefit partners? How does VCloud Air Network help address my issues? What happens once I have selected progression and completed the application? How do I progress to cecome an active service provider? Usage Meter and Reporting Version 3.
Why do you require the appliance to be Installed? How do you install or upgrade Usage Meter? What is the latest supported version of Usage Meter you need to install to submit monthly usage? How do you generate A Monthly Usage Report? What are the different types of reports that can be generated from Usage Meter 3. How could you ensure the usage reported is accurate and correlates with production VMs in its environment?
After upgrading the Usage Meter Tool, what are the differences when comparing the Usage Reports with the previous version? I am unable to login to the Usage Meter Browser User Interface, what are the steps required to recover the password? What are the steps and commands to reset the password? How can you report issues with the Usage Meter Tool? Why should you check to ensure that there are no metering issues? How could you verify the products and bundles used are correct in the reports?
What are your benefits for moving into Flex model? What are the impacts of not moving into the Flex model? Do you automatically move to Flex upon your Contract Renewal? What is Core and the products included in it? What are the add-on products and points associated within the Flex model? When are you required to transition into Flex? What is the process to report monthly usage for Flex? How are vCloud SP bundle points compared to Flex? How long will the promotional point discounts available? What are the different NSX editions available through Flex?
How does the features differ from each edition? What are the possible scenarios that you need to be aware of when upgrading from vCloud SP Standard bundle 5-points to Flex? What is vRealize Operations Chargeback? Does Usage Meter detect this product and apply usage separately? What if you are having a Custom pricing or Custom product bundles? Do you need a new version of vCloud Usage Meter to meter Flex pricing? If you are using vCloud Usage Insight to automate reporting, would that continue to work with using the Flex pricing model?
What do you need to complete immediately? What are the various requirements on progressing to Partner Tiers? What are the current concerns with VIBs? What is an Image Profile?
What is Software Depot? Citrix General Why Citrix and rhipe? What is the Program? What are the requirements of the program? What are the technical requirements of the program? Is there a minimum commitment? Does the partner need training? Is the program a consumption or usage based program? Where do I find a price list?
What are the benefits of the program to the partner? What's in it for me as a partner using Citrix and Microsoft? Does Citrix and Microsoft assist with removing costs from my business? Where can I find more information? What are the issues that Skype for Business Optimisation helps to address? What's in it for me as a partner using Skype for Business Optimisation using Citrix?
Does Skype for Business Optimised help me address new markets? Does Skype for Business Optimised assist with removing costs from my business? Where do I find more information about Skype for Business Optimised? What are the issues that O on Citrix helps to address? Does O on Citrix help me address new markets? Does O and Citrix assist with removing costs from my business? What are the issues that NetScaler helps to address? What's in it for me as a partner using NetScaler? Does NetScaler help me address new markets?
Does NetScaler help me remove cost from my business? Where do I find more information about NetScaler? Why would a partner use XenApp Premium? What are the Issues that XenApp Premium helps to address? What's in it for me as a partner using XenApp Premium?
Does XenApp Premium help me address new markets? Where can I find more information on XenApp Premium? What are the issues that XenApp helps to address? What's in it for me as a partner using XenApp? Does XenApp help me address new markets? Does XenApp help reduce costs for my business? Where do I find more information on XenApp?
Does XenApp help reduce costs from business? What are the issues that ShareFile helps to address? Does ShareFile help me address new markets? Does ShareFile help me remove cost from my business? Where do I find more information about ShareFile? Can users move between Commit and Flex licenses? Acronis Why rhipe and Acronis? Why Rhipe? Why Acronis? Why Rhipe And Acronis? Why Use Acronis Backup Cloud? The NetScaler uses vServers virtual servers to deliver different kinds of services, in this case the vServer will be configured as a gateway server.
Just remember that you can configure multiple independent vServers on the same NetScaler serving different purposes, like a load balancing or SSL offload vServer for example.
When a SNIP address is configured, a corresponding route is added to the NetScalers routing table, which is used to determine the optimal route from the NetScaler to the internal network. A SNIP address is not mandatory. In that case it will also be used as the source IP address. Only when the configured MIP address is the first in the subnet it the NetScaler will add a route entry to its routing table. Hopefully the overview below will help in clarifying some of the concepts mentioned throughout this article.
Up close and personal. Ok, so what happens? Lets take it step by step. ICA file generation etc. An external user will contact the NetScaler Gateway over port 80 or preferred. This is indicated as the VIP followed by the 1 vServer. Load balancing is just what it sounds like, taking a single workload serving up email, webpages, etc.
If we are load balancing application traffic to make sure each end user gets the best experience, we need to know how healthy the servers are that we are balancing the traffic for. If one of the servers is not healthy, we want our Application Delivery Controller to be smart enough to limit or suspend the traffic it sends that server so the person at the other end making the request has a good experience.
Surfing the web is hard, if you are the devices making all of the connections to the web pages you want to see and then subsequently breaking those connections when you move on to the next page. All of this connecting and disconnecting adds overhead which can show up as delay and slowness to the person making the request.
TCP Multiplexing lets a NetScaler make a quick check to see if it has an existing connection can be used instead of creating a brand new connection each time.
The ADC can act as the middle man, taking care to both answer the request from the person and not overwhelm the server containing the information.
The result is a better user experience and getting more performance from each application server, reducing hardware costs. When you send something securely, each little packet of information has to be wrapped up in a special package and encrypted before it goes across the Internet. When each little packet of information arrives at its destination, it has to be unwrapped and delivered to the person making the request.
All of this wrapping and unwrapping takes a considerable amount of time and resources to execute. By moving this functionality to the Application Delivery Controller ADC we reduce the burden on the servers, freeing them up to churn out more data and again giving them more capacity potentially reducing the number of servers needed for the task..
The ADC becomes responsible for verifying proper authorized authentication instead of the application server. This allows the application servers to do what they do best, deliver applications. The concept is a simple one.
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