frame relay

Answered Question
Mar 29th, 2009

Hi every body!

I have few questions about frame relay.

1) When a client orders a frame relay service, what information/configurations are provided by telco besides dlci?

2)The lapf header and trailer does not have protocol type feild. Cisco and three other companies created an additional header which comes between the lapf header and layer 3 packet. It includes a 2 byte protocol type feild.

What were the those three companies? Does it mean the routers from these companies can work together using " cisco encapsulation" since these companies together created this header to make up for the absence of protocol type field in lapf header and trailer?

Thanks a lot!

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Correct Answer by Giuseppe Larosa about 7 years 8 months ago

Hello Sarah,

1) a FR PVC is defined by the DLCI and by the traffic parameters that can apply to it: CIR, burst rate, MBR and so on

These are contracted but can be used to implement effective FR traffic shaping

2)

This is a too old story since 1992 a standards based protocol type optional field has been added to FR.

So FR IETF encapsulation allows for multiprotocol too.

see

http://www.rfc-editor.org/rfc/rfc1294.txt

and later RFC 2427

the real difference is in HDLC where Cisco HDLC has a protocol type and standard HDLC hasn't at all.

Hope to help

Giuseppe

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Correct Answer
Giuseppe Larosa Mon, 03/30/2009 - 01:19

Hello Sarah,

1) a FR PVC is defined by the DLCI and by the traffic parameters that can apply to it: CIR, burst rate, MBR and so on

These are contracted but can be used to implement effective FR traffic shaping

2)

This is a too old story since 1992 a standards based protocol type optional field has been added to FR.

So FR IETF encapsulation allows for multiprotocol too.

see

http://www.rfc-editor.org/rfc/rfc1294.txt

and later RFC 2427

the real difference is in HDLC where Cisco HDLC has a protocol type and standard HDLC hasn't at all.

Hope to help

Giuseppe

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