While a protocol as a whole, may be comprised of more than one header type that it uses for communication purposes to exchange information such as state and transmit application specific data. This is the reason why sometimes a protocol is described as a protocol suite.
Since January 1, 2006, U.S. employers have been allowed to amend their 401(k) plan document to allow employees to elect Roth IRA type tax treatment for a portion or all of their retirement plan contributions. The same change in law allowed Roth IRA type contributions to 403(b) retirement plans. Employees can roll their Roth 401(k) contributions over to a Roth IRA account upon termination of employment. 2  It is the employer's decision whether to provide access to the Roth 401(k) in addition to the traditional 401(k).
A 401(k) is a retirement account. It is different from some other retirement accounts because they allow capital gains, dividends and interest to grow tax-free (or tax-deferred). However, there are limits on how much you can contribute and restrictions on when and how much you can take out. It is an employer-sponsored retirement plan. Your contributions are deducted from your paycheck. The 2014 contribution limit to this plan is $17,500 for employees under age 50.