Subject: Support of Frame-Relay RFC1490 SNA Encapsulation

From: [email-masked]
Date: Thu, 22 Jun 95 07:27:47 EDT

*** Reply to note of 06/21/95 01:30                                            
From: Jean-Pierre Marce                   TEL: (33) 92 11 45 83                
      3745 and 3746-900 Design, NHD La Gaude                                   
      E-MAIL: IBMMAIL(FRIBMB9D)           FAX: (33) 93 24 75 12                
Subject: Support of Frame-Relay RFC1490 SNA Encapsulation                      
                                                                               
As far as my box is concerned we don't want to drop the RFC1490                
routed format created by Rao Cherukuri that we used between APPN               
nodes (and also for INN and BNN traditional subarea traffics).                 
                                                                               
1.RFC1490 routed format gives the lowest overhead for DLC purpose and          
  is used for point to point connection between DTEs or for DTE to DTE         
  connection across a frame relay bearer services.                             
  Overhead by frame is 16 bytes, including heading and trailing flags.         
  On a 19.2 Kbps line it's already a big overhead mainly for                   
  isolated acknowledgments when they occur.                                    
2.For APPN and HPR, as we are using frame relay on a single hop                
  communication between adjacent nodes, the RFC1490 bridged format             
  would not make sense: which MAC addresses will be coded in the               
  format?                                                                      
3.RFC1490 routed format is supported by 3745/NCP, 3746-900, 3174 and by        
  a lot of non IBM routers.                                                    
4.RFC1490 bridged format for token ring, called BAN, has an overhead which     
  can go up to 50 bytes.                                                       
                                                                               
I agree with Jim Cobban that supporting three formats to solve almost          
the same problem is not efficient. BAN provides a dynamic support              
for DSPUs in a SNA gateway; when this gateway supports DLUR, the DSPUs         
should be supported by DLUR and the SNA and APPN traffic should be             
transported with RFC1490 routed format to the adjacent APPN/HPR node.          
                                                                               
Regards, Jean-Pierre.

---

From: "Derek Bolton" <[email-masked]>
Date: Fri, 23 Jun 95 08:26:07

Jim,

As one of the original authors of RXR/2, I can assure you that it supports 
both the bridged (encapsulated 802.5) format and Rao Cherukuri's routed 
format.  And the reason for supporting both was that, at that time, 6611 
supported one while NCP supported the other.

Regards,
  Derek Bolton