RE: [j-nsp] isis question

From: Chris Flores (chris.flores@onfiber.com)
Date: Wed Apr 25 2001 - 16:56:07 EDT


My response to #1 is in-line.
 

-----Original Message-----
From: Naidu, Venkata [mailto:Venkata.Naidu@Marconi.com]
Sent: Wednesday, April 25, 2001 10:40 AM
To: juniper-nsp@puck.nether.net
Subject: RE: [j-nsp] isis question

Hi Chris
 
I had this question for a long...
* If IS-IS is not using any L3 (CLNP/IP) then
  those IS-IS routing packets can't be forwarded beyond
  1 hope. For example, OSPF packets can be forwarded
  or flooded more than 1 hope in Virtual neighbor
  environment. Am I correct or missing something?
 
CF: An IS floods LSPs on all interfaces within the same level or area. A
particular LSP contains a 32-bit sequence number which qualifies the LSP
within the LSDB. When an IS receives a new LSP from a neighbor, it first
compares the sequence number with one it already has in its LSDB. If the
received sequence number is greater or the LSP was not present in the LSDB,
the IS stores the LSP and marks it for ackknowledgement. Subsequently, the
LSP is flooded on all the interfaces within the same level or area. This
process is repeated on each IS within the same level or area. I hope this
answers your question.
 
* If IS-IS packets are forwarded directly over L2
  then how does it cope up with fragmentation and
  reassembly services. I am not able to visualize
  how IS-IS packets will be transmitted over different
  L2 technologies like ATM and broadcast/multicast capable
  networks etc. How they get code-points?
 
Thanks & Regards --
http://www.geocities.com/kvsnaidu <http://www.geocities.com/kvsnaidu>

-----Original Message-----
From: Chris Flores [mailto:chris.flores@onfiber.com]
Sent: Wednesday, April 25, 2001 10:59 AM
To: 'zheng jiang gu'; mpls-ops@mplsrc.com; juniper-nsp@puck.nether.net;
Aviva Garrett
Subject: RE: [j-nsp] isis question

My response is in-line. I hope it helps...

-----Original Message-----
From: zheng jiang gu [mailto:zjgu@ce-air.com]
Sent: Tuesday, April 24, 2001 9:15 PM
To: mpls-ops@mplsrc.com; juniper-nsp@puck.nether.net; Aviva Garrett
Subject: [j-nsp] isis question

hi all:
   When I study isis, I meet the problem:
1 Which network layer use to encapsulation isis-pdu?
Is it clnp or ip?
 
CF: The OSI packets (or PDUs) are forwarded "as is" or transmitted directly
over the underlying link layer without the need for encapsulation - per RFC
1195.
 
2 How many IS-IS adjacency between point-to-point routers?
 
CF: IIH (IS-IS Hello) PDUs are utilized to initialize and maintain
adjacencies between neighbors. On a p2p link, one neighbor creates one
adjacency. Do you have a more specific question that needs answering?
 
br
shawn<?xml:namespace prefix = o ns =
"urn:schemas-microsoft-com:office:office" />



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