From the Government of Canada Immigration website.
The Student Direct Stream (SDS) is an expedited study permit processing program for those who are applying to study in Canada at a post-secondary designated learning institution (DLI). The SDS is available to legal residents who also reside in

China
India
Morocco
Pakistan
Philippines
Senegal
Vietnam
To be eligible, applicants must meet specific requirements by providing documentation up front.

About the SDS
Some international students can get their study permits faster by using the SDS. IRCC processes most SDS applications within 20 calendar days if the eligibility requirements are met. Only applications submitted electronically are eligible for SDS processing. All paper applications are processed under the regular study permit application stream and are subject to the associated processing times. Foreign nationals who are eligible for SDS processing are still subject to all other eligibility and admissibility requirements under the Immigration and Refugee Protection Act (IRPA) and Immigration and Refugee Protection Regulations (IRPR).

Eligibility criteria
The applicant must include the following documents to be eligible for SDS processing:

proof of a valid language test result, completed within 2 years of the date the SDS application was received, showing either of the following:
an International English Language Testing System (IELTS) score of 6.0 or higher in each language skill: listening, reading, writing and speaking
a Test d’Evaluation de Français (TEF) score that is equivalent to a Canadian Language Benchmark (CLB) score of at least 7 for each ability: at least 310 for speaking, 249 for listening, 207 for reading and 310 for writing
proof of a Guaranteed Investment Certificate (GIC) of CAN$10,000 or more from any bank insured by the Canadian Deposit Insurance Corporation (CDIC) or any bank listed on the IRCC SDS web page

The GIC must meet the following criteria:

When the GIC has been purchased, the bank provides a letter of attestation, the GIC certificate, the Investment Directions Confirmation or the Investment Balance Confirmation to the applicant.
The bank holds the funds in an investment account or a student account that is inaccessible for release to the applicant until the applicant’s arrival in Canada.
Upon entry to Canada, the bank must validate the client’s identity before releasing funds to the study permit holder.
The applicant receives an initial disbursement upon identifying themselves, and the remaining funds are disbursed in monthly or bimonthly installments over a period of 10 to 12 months.
proof of full payment of tuition for the applicant’s first year of study

This may be in the form of the following:

a receipt from the DLI
an official letter from the DLI confirming payment of tuition fees
a receipt from a bank showing that tuition fees have been paid to the DLI
proof that the tuition fee amount has been transferred into a repository account at the DLI to be applied to the tuition bill at a later date
letter of acceptance from a post-secondary DLI
most recent secondary or post-secondary educational transcripts
proof of completion of upfront medical examination from a panel physician for applicants
who have lived or travelled for 6 months in designated countries or territories during the year before coming to Canada
whose field of study requires upfront medical examination results
Note: The medical examination confirmation may be either an information sheet printout, if the physician uses eMedical, or an Upfront Medical Report form [IMM 1017B].

In addition to the above criteria, applicants for SDS processing must include as part of their electronic application (e-application) additional documents. For complete information about SDS, please visit this link.