So given the information AS A is a customer of AS B and AS E, and A is peering with AS C and AS D;
From what I understand, in the first step, we have to discard the routes with the lower local preferences. In this case, A is a customer of B, then that path has a greater local preference or lower local preference?
Below I attach the whole exercise in case I missing some important data:
From what I understand, in the first step, we have to discard the
routes with the lower local preferences.
Correct, one of the very first steps in the BGP best path selection algorithm is to prefer paths with the highest LOCAL_PREF (= discard paths with lower LOCAL_PREFs)
See https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html for more details.
In this case, A is a customer of B, then that path has a greater local
preference or lower local preference?
It is customary to give paths received from a customer a higher LOCAL_PREF (= more preferred) than paths received from peering partners or transit providers.
See https://www.noction.com/blog/what-you-should-know-about-bgps-local_pref for more details.
Related
For my internship, I need to implement a blockchain based solution to manage a drug supply chain. The management of this supply chain implies to track-and-trace (geolocate) a drug on the chain, but also to monitor the storage temperature to see if the cold chain is respected. For that I created a mock-up of the POC my Dapps (https://balsamiq.cloud/sum5oq5/p8lsped)and also I wanted to prepare myself by doing a UML and a use cases. However, I didn't find a lot of information about blockchain's UML and use cases besides two literatures which were quite different, so I don't know if what I did was correct or not...
The users of my Dapps will be the following ones:
The stakeholders (Manufacturers, Distributors and Retailers) which will use the Dapps to place orders and also monitor them. They also can search in the historic a specific order. Finally, trough IOT sensors they update the conditions of the order (temperature & location).
The administrator which roles is to update the Dapps and its rules. But also to add or delete user while also defining the rights that they have on the blockchain (I intend to use a permisionned blockchain). Finally, they are also here to help in case of technical problem.
The Dapps that I'm thinking about works in the following:
A user, the customer, can place an order (a list of products) to a
certain seller and choose the final destination of the order.
The order is then put together before being shipped or stocked in the
depots of one of the stakeholders (distributor or retailer) with a
description of the stocking and/or shipping condition of the product
(for example the product must be stocked or transported in a room
with a temperature of less than 5°C). During the shipping and
storing, an IOT device will feed the drops with the temperature and
geolocation of the product by updating the data each 5-10mn.
Obviously they will be a function that allows all the users to see
the history of the order passed and search inside a specific order.
In case where the temperature doesn't respect the temperature
recommended, then the smart-contract send an alert. The same if the
collocation of the product is "weird" like being in some European
countries and not in an Asian country, an alert will be sent again by
the smart-contractual. Finally, in the case where the product is sent
to the asked location by the customer, then the money for the order
will be paid to the seller.
So based on what I explained, I came here in hope that someone tell me if the use cases and UML that I did were correct or not.
I thank in advance anybody who'll take the time to help me.
We write app.example.com instead of com.example.app in major DNS-based systems, including WWW, FTP, and email. What is the reason behind this design? Why not the reverse order?
Hostnames existed before the DNS and even before TLDs.
Structures to the names have been added through RFC 921 "Domain Name System Implementation Schedule - Revised" (October 1984)
This document explains the change from simple names (no dot) to hierarchical ones, and this was needed because the Internet was growing at that time and a single flat list of names was not enough to describe every hosts.
Some excerpts:
The names are being changed from simple names, or globally unique
strings, to structured names, where each component name is unique
only with respect to the superior component name.
...
The elements (or components) of the structured names are separated
with periods, and the elements are written from the most
specific on the left to the most general on the right.
For example: USC-ISIF.ARPA
RFC 882 "DOMAIN NAMES - CONCEPTS and FACILITIES" (November 1983) just says it is a convention:
The domain name of a node or leaf is the path from
the root of the tree to the node or leaf. By convention, the
labels that compose a domain name are read left to right, from the
most specific (lowest) to the least specific (highest).
A clue may come from RFC 1034 "DOMAIN NAMES - CONCEPTS AND FACILITIES" (November 1987) that repeats the above with some details:
The domain name of a node is the list of the labels on the path from
the node to the root of the tree. By convention, the labels that
compose a domain name are printed or read left to right, from the most
specific (lowest, farthest from the root) to the least specific
(highest, closest to the root).
RFCs (see RFC 1166) have the tradition to use the "MSB 0" bit numbering: it means that when you write down a byte, with 8 bits, you start with the most significant one, the bit with highest value (the encode encoding for the 128 decimal value).
This was then extended with the concent of network byte order, where the most significant one is firsts.
I guess that the idea of starting with the most specific label of the name comes directly from this idea of the most specific bit first, which means starting with the label farthest from the root and hence finally having the root at the top right side and then reading a full name in a kind of right to left pattern.
I have a column which is made up of addresses as show below.
Address
1 Reid Street, Manchester, M1 2DF
12 Borough Road, London, E12,2FH
15 Jones Street, Newcastle, Tyne & Wear, NE1 3DN
etc .. etc....
I am wanting to split this into different columns to import into my SQL database. I have been trying to use Findstring to seperate by the comma but am having trouble when some addresses have more "sections" than others. ANy ideas whats the best way to go about this?
Many THanks
This is a requirements specification problem, not an implementation problem. The more you can afford to assume about the format of the addresses, the more detailed parsing you will be able to do; the other side of the same coin is that the less you will assume about the structure of the address, the fewer incorrect parses you will be blamed for.
It is crucial to determine whether you will only need to process UK postal emails, or whether worldwide addresses may occur.
Based on your examples, certain parts of the address seem to be always present, but please check this resource to determine whether they are really required in all UK email addresses.
If you find a match between the depth of parsing that you need, and the assumptions that you can safely make, you should be able to keep parsing by comma indexes (FINDSTRING); determine some components starting from the left, and some starting from the right of the string; and keep all that remains as an unparsed body.
It may also well happen that you will find that your current task is a mission impossible, especially in connection with international postal addresses. This is why most websites and other data collectors require the entry of postal address in an already parsed form by the user.
Excellent points raised by Hanika. Some of your parsing will depend on what your target destination looks like. As an ignorant yank, based on Hanika's link, I'd think your output would look something like
Addressee
Organisation
BuildingName
BuildingAddress
Locality
PostTown
Postcode
BasicsMet (boolean indicating whether minimum criteria for a good address has been met.)
In the US, just because an address could not be properly CASSed doesn't mean it couldn't be delivered - cip, my grandparent-in-laws live in enough small town that specifying their name and city is sufficient for delivery as local postal officials know who they are. For bulk mailings though, their address would not qualify for the bulk mailing rate and would default to first class mailing. I assume a similar scenario exists for UK mail
The general idea is for each row flowing through, you'll want to do your best to parse the data out into those buckets. The optimal solution for getting it "right" is to change the data entry method to validate and capture data into those discrete buckets. Since optimal never happens, it becomes your task to sort through the dross to find your gold.
Whilst you can write some fantastic expressions with FINDSTRING, I'd advise against it in this case as maintenance alone will drive you mad. Instead, add a Script Transformation and build your parsing logic in .NET (vb or c#). There will then be a cycle of running data through your transformation and having someone eyeball the results. If you find a new scenario, you go back and adjust your business rules. It's ugly, it's iterative and it's prone to producing results that a human wouldn't have.
Alternatives to rolling your address standardisation logic
buy it. Eventually your business needs outpace your ability to cope with constantly changing business rules. There are plenty of vendors out there but I'm only familiar with US based ones
upgrade to SQL Server 2012 to use DQS (Data Quality Services). You'll probably still need to buy a product to build out your knowledge base but you could offload the business rule making task to a domain expert ("Hey you, you make peanuts an hour. Make sure all the addresses coming out of this look like addresses" was how they covered this in the beginning of one of my jobs).
I'm writing a Regex to validate email. The only one thing confuse me is:
Is it possible to have single character for top level domain name? (e.g.: lockevn.c)
Background: I knew top level domain name can be from 2 characters to anything (.uk, .us to .canon, .museum). I read some documents but I can't figure out does it allow 1 character or not.
It is technically possible, however, there are no single character tlds that have been accepted into the root (as of the moment) so the answer is:
Yes, it is possible to have single character for top level domain name, however, there are currently no single character TLDs in the root.
You can see the list of TLDs that are currently in the root at this URL:
http://data.iana.org/TLD/tlds-alpha-by-domain.txt
RFC-952 shows what a "name" is, this includes what is valid as a top level domain:
A "name" (Net, Host, Gateway, or Domain name) is a text string up
to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus
sign (-), and period (.).
Additionally, the grammar from RFC-952 shows:
<name> ::= <let>[*[<let-or-digit-or-hyphen>]<let-or-digit>]
RFC-1123 section 2.1 specifically allowed single letter domains & subdomains, changing the initial grammar of RFC-952 from starting with just a letter to being more relaxed, so now you are allowed to have single letter top level domains that are a number:
2.1 Host Names and Numbers
The syntax of a legal Internet host name was specified in RFC-952.
One aspect of host name syntax is hereby changed: the
restriction on the first character is relaxed to allow either a
letter or a digit. Host software MUST support this more liberal
syntax.
EDIT: As per #mr.spuratic's comment, RFC-3696 section 2 tightened the rules for top level domains, stating:
There is an additional rule that essentially requires
that top-level domain names not be all-numeric.
This means that:
a. is a valid top level domain
1. is not a valid top level domain
A very unscientific test of this shows that if I add "a" into my hosts file pointing to my local machine, going to http://a in my address bar does show my Apache welcome page.
I'm not sure about the internet standard, but in practice, no.
See,
http://www.norid.no/domenenavnbaser/domreg.html
and,
http://sqa.fyicenter.com/Online_Test_Tools/Domain_Name_Format_Validator.php
You should DEFINITELY allow 1-character domains since some registries allow them not by accident (and I speak of quite big registries like UK, Germany, Poland, Ireland too - so important contributors to the Internet community, not oney exotic small exceptions). Since I also plan using such domains, that definitely work also with all e-mail services I used, letters AND numbers, I really would give the hint to allow this, else your script might need later correction.
Also some of the biggest internet companies use such domains - one of the most famous examples is Twitters t.co for shortening. Other companies I know of who have such domains are Facebook, Google, PayPal, Deutsche Telekom. But the list is longer and also some bigger investors hold them as assets.
By the way as proof there is a website trading this kind of domains online if You search for "1 letter domain names" :)
I need a script to find out what is the lowest available domain name with a give TLD (say .com, .info, or .net).
For example, 1000423.com is free but 1000.com is taken.
Probably my spammiest question so far.
NOTE
I mean "lowest" domain name numerically (i.e. 1.com, 2.com, 3.com, ..., n.com, n+1.com, ...) and not shortest as in String.length.
In your web-capable language of choice:
Ask the user for a top-level domain name.
i <- 0.
Send out an HTTP GET to a registrar to see if "i.(tld)" is taken.
If it's not taken, notify the user and quit.
i <- i + 1.
Go to step 2.
You may need to add a loop delay to avoid the registrar thinking that you're trying to do a DOS attack.
Unfortunately, as far as I know, there's no central repository saying that a certain domain name is or isn't for sale. You'll have to look up a domain name and see if it's owned by any of the major domain name vendors (GoDaddy, etc.)