[e2e] Types Of Service

David P. Reed dpreed at reed.com
Mon Jul 28 12:25:41 PDT 2003

I disagree - the protocols are defined to optimize a particular type of 

TCP provides high reliability end-to-end.   Modifying the size of its 
checksum and encrypting its payload including a virtual header is all that 
you would need to increase its reliability to an arbitrary level.

RTP provides lowest jitter for a data stream where loss is not a problem 
(error correction adds jitter by definition).

UDP has no QoS goals - it exists to enable protocols like RTP to be 
dispatched at the endpoints to the right process that implements the protocol.

Luby's Digital Fountain (over UDP) provides most efficient goodput on a 
noisy channel for messages that occupy many packets (efficiency = 
goodput/total_transmitted; for Digital Fountain efficiency ~ 1 - packet 
error rate, which is optimal).

At 03:42 PM 7/28/2003 -0300, Fernando Gont wrote:
>In the same paper (David Clark's) as that of my previous post, it's stated 
>that "The second goal of the Internet architecture is that it should 
>support, at the transport service level, a variety of types of service.".
>However, only TCP, UDP, and RTP (which is built over UDP) come to my mind, 
>they don't guarantee any specific type of service (for example, "low 
>delay", "high throughput", etc.) by themselves.
>Besides that, for example, TCP provides a "realiable" byte stream. 
>However, there are some errors that TCP won't catch, so if reliability is 
>a real issue, then another layer of error control must be built up on top 
>of TCP.
>Have there been any efforts (I *do* think so) in developing transport 
>protocols that focus on providing different types of service ("low delay", 
>"high throughput", "true (?) reliability", etc. ) ?
>Pointers to any papers discussing the problems and efforts around this 
>will be appreciated, too.
>Fernando Gont
>e-mail: fernando at gont.com.ar || fgont at acm.org

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