LLD stand for Low Level Document. This is the last and final document for ICT Implementation Project. When you will get sign-off from customer on successful UAT, then its time to submit the final project details to get project signoff.
Purpose of LLD:
- Officially successfully Project closure document
- Officially document to get project sign-off
- SI/Vendor/OEM are eligible to invoice
- Now Project is ready to handover Operation team.
Difference between HLD and LLD:
In High Level Document (HLD) SI/Vendor/OEM proposed a solution with an expected result and a have road-map that how this project will be implemented, which technology going to used, time lines etc. But in LLD we mentioned Actual implementation journey.
How to Prepare LLD
As we already discuss that LLD is the document where we need to capture all actual implementation report, data and information.
Below are some information which we need to capture in LLD:
- Brief Introduction
- Purpose of this document
- Agreed SOW
- Assumptions and Caveats
- Reference documents
- Detailed Implemented Network Architecture ( Link level, device level, Rack level etc)
- Detailed IP Schema & VLAN information
- Detailed Technology used ( Protocol, Routing and Switching protocols)
- Detailed Inventory
- Detailed Packet flow and traffic
- Actual Configuration of every devices
- Any deviation or Changes as per HLD or RFP
Information should be part of LLD
- Brief Introduction : This section will cover some brief introduction of Project and its requirement.
- Purpose of this document : Need to explain why we are preparing this LLD and what is the requirement and what all information you are going to capture or share. Customer, SI/Vendor details.
- Agreed SOW : Detailed SOW which is already agreed in HLD.
- Assumptions and Caveats : It will cover like this document is prepared based on HLD and it has been assumed that Customer and other stockholders are aware about this project and what we agreed in HLD.
- Reference documents : What all document has been refered during this implementation like:
- RFP
- HLD
- OEM Product Data sheet and configuration guides
- Any specific compliance Guidelines
- Detailed Implemented Network Architecture : This is very important part of LLD because in HLD we only share high level network architecture, but in LLD it will be in details and need to explain each and every connectivity. Below are some network diagram which needs to be explain in LLD:
- Link Level : How Devices are connected, What is use, Link Capacity, HA connectivity everything.
- Device Level : How devices are connected, what is their Role, their feature, HA etc.
- Protocol Level : Which Protocol is running and why
- Rack Level : How Devices installed in Racks, Rack Labelling, Rack Unit (RU) wise hardware details, Rack level redundancy, Hardware level Redundancy, Power Level Redundancy etc
- Cabling and Labelling : How Cabling are structured for Intra-Rack device connectivity, Inter-Rack device connectivity with proper Labling to understand easily.
I know it is looking simple in writing and reading, but when you are doing is practically you will find that things are not as easy as we think. It required lots of efforts to prepare such diagram, gathering information, documenting correctly, but before that you should have proper network architecture. It should not be much complicated.
Note: Always try to plan and design the network in simple way not complicated. Some time we design the network in very Un-professionally or un-structured. Some time we design, Config or connect the devices to just complete the project or to show case to customer that services is running, but in background there are lots of Gap that might Customer can not identify during UAT or project sign off. But once you handover to Operation team then it will be very difficult for them to manage or troubleshoot the network. So always try to design and implement the network that easy to understand and manage.
Technical Information
- Detailed IP Schema & VLAN information : in HLD we only share IP Subnet. But in LLD we need to share detailed IP Schema for each and every devices. Their Management IP, Loop-back IP, Vlans, subnet mask, Gateways etc. Also need to share how much IP address are reserved or available for future use.
- Detailed Technology used (Protocol, Routing and Switching protocols): Although which technology needs to configure that is already decided and agreed in HLD, but exactly on which devices and what exactly configuration has been done, that needs to explain in detail in LLD.
- LAN : Everybody knows that LAN is very critical part of if any ICT network design. In HLD we simply explain that what hardware and technology will be used. But in LLD need to explain in details that on how LAN network built and what all technology used and Why and how.
WAN : In some project there are multiple remote locations which needs to connect with HQ DC. For such solution WAN solution is required like,
- Which WAN protocol using and why
- Which ISP services taken
- What all services implemented for remote location.
- How traffic flow
WIFI : Wireless solution is same as LAN. To setup a WiFi network or solution needs to capture below information
- WLC Model details and its specification
- Basic configuration
- SSID Details
- WIFI VLAN Details
- DHCP Subnet
- Access Points Details
- Site Survey or Heat Map reports
Security : Security is always a major concern for IT/ICT network. All Security Parameter/access should be clearly agreed with customer. Like what rules, Policies, ports, ACLs, Ext Firewall, Int Firewall, all should be clearly designed and agreed with customer.
Server, DB, Storage- MZ : All services, tools, productions are stored in Servers, storage and DB. These are kind of Locker for any project and required extra security and only Authorized person have access for these servers. During Solution finalization Sizing of Server is required expertise as it will cater all current and future data. We need to size these server with respect to Future requirement as well. These servers should be secure with Militarized Zone (MZ) behind the internal Firewall.
During Sizing of server few thing need to consider that:
- Gathering requirement for all services
- Total CPU
- RAM
- Operating Software
- Compute
- Servers details ( Blade server or Rack Servers)
- HDD
Web-Server- DMZ : Same as MZ, need to configure De-Militarized Zone ( DMZ) for WEB servers to access the services over web.
Hardware and Passive Details
Detailed Inventory : If you remember, then we have already discuss that before start implementation we need to perform POST for all devices and during POST we capture all inventory details. But in LLD now we have actual inventory that is used. Below are sample format for Inventory list.
Detailed Packet flow and traffic : In HLD we only present high level packet flow or traffic flow. But in LLD, it is actual, and need to explain in details. We can take some referenced from UAT document as well for this section.
Actual Configuration of every devices : It requires complete configuration, including booting sequence, Post, and other configuration details. This Configuration should be direct captured from devices and should not make any manual correction. Configuration should contain proper Banner, Passwords should not be in plane text, it should be encrypted. During sharing configuration do not share any Password. All username and Passwords will be shared separately and securely with customer only.
Tools Details: In any technical project tools are very important part of the project. These tools are used to monitoring, reporting or managing the devices. These tools required special expertise to install. There are some specific hardware requirement. Although these hardware requirement already factors in BOQ, but now we need to show how we have used that hardware like Processor, RAM, Flash, HDD Storage.
Inter/Intra Rack cabling details : As we discussed in above section that Physical connectivity details are very much important to explain and share with Customer, so that customer or operation team have clear picture that what device are connected to with port or device.
Below are Sample format to prepare and share Inter/Intra Rack cabling details :
Document Acceptance : LLD should be both party singed and approved ( Customer and SI/Vendor).
Conclusion
LLD is final and official sing off of project, that project is completed successfully. Now network is ready to run, Go live and ready to handover to customer for Operation.
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