Re: [ns] Specifying arbitrary node addresses

[Sean Murphy <murphys@Teltec.DCU.IE>]

> > I had a look at hierarchical addressing, but I'm quite sure that this
> > carries hierarchical routing baggage with it. Can someone confirm
> > this? Afaik, this then imposes constraints on the addresses chosen for the
> > nodes. This is not what I want. Is it possible to decouple hierarchical
> > addressing from hierarchical routing?
>
> This would be ideal if done - the existing flat address space can (and
> IMO should) be thought of as hierarchical addressing with one level of
> hierarchy.

I had a look at the way that hierarchical addressing and routing are
implemented, but it seemed like a bit of a nightmare to start changing. I
didn't like the fact that the address was stored in a tcl variable as a
string of dotted quads, and seemed to be manipulated in this format. I
still haven't figured out how packets are assigned a 32-bit address.

I did hack together some (rather unsubstantial) changes to the way that
flat routing is implemented. I added code to enable a node address to be
specified (either in dotted quad format or as some abstract number) and I
modified the routing tables in each node so that node address is used to
index the table rather than the node id.

If these changes are made to the code a node can now be added as follows:
	set n(0) [$ns node 1.0.0.1]
or
	set some_arbitrary_node_number 89753
	set n(0) [$ns node $some_arbitrary_node_number]
I only wrote it to work with generic nodes, so I don't know if it will
cause other things to break.

I made the changes to a bastardised version of ns-2.1b6 - I think that the
files I changed are the same as those in ns-2.1b6, but I've provided
context diffs in any case.

One rather obvious caveat - allowing such control over the node addresses
has the potential to go pear-shaped: multiple nodes having the same
address can now exist in the network.

Sean.

-----
Sean Murphy,			Email: sean.murphy@teltec.dcu.ie
Teltec Ireland,			Phone: +353-1-7045080
DCU, Dublin 9,			Fax:   +353-1-7045092
Ireland.

*** ns-address.tcl	Wed Jun 21 16:17:42 2000
--- ns-address.tcl.old	Wed Jun 21 15:31:09 2000
***************
*** 432,467 ****
  	}
  	error "get-node-id-by-addr:Cannot find node with given address"
  }
- 
- proc convert-dotted-ip-to-number {dottedipaddr} {
-     if { [string first "." $dottedipaddr] == -1 } {
- 	return $dottedipaddr
-     }
-     set fields [split $dottedipaddr .]
-     if { [llength $fields] > 4 } {
- 	puts "IP Address contains more than 4 fields"
- 	exit 1
-     }
- 
-     set addr(0) [check-field-value [lindex $fields 0]]
-     set addr(1) [check-field-value [lindex $fields 1]]
-     set addr(2) [check-field-value [lindex $fields 2]]
-     set addr(3) [check-field-value [lindex $fields 3]]
- 
-     # puts "0 = $addr(0), 1 = $addr(1), 2 = $addr(2), 3 = $addr(3)"
-     set addressnumber [expr "$addr(3) + ($addr(2) << 8) + \
- ($addr(1) << 16) + ($addr(0) << 24)"]
- 
-     return $addressnumber
- }
- 
- proc check-field-value {fieldvalue} {
-     if {$fieldvalue == "" } {
- 	return 0
-     }
-     if { $fieldvalue > 255 } {
- 	puts "dotted IP address must contain fields in range (0-255)"
- 	exit 1
-     }
-     return $fieldvalue
- }
--- 432,434 ----

*** ns-node.tcl	Wed Jun 21 16:19:35 2000
--- ns-node.tcl.old	Wed Jun 21 14:26:57 2000
***************
*** 73,89 ****
  }
  
  Node instproc set-node-address { args } {
-     $self instvar address_
-     # this assumes that args contains a single address (either dotted IP, or
-     # abstract number)
-     
-     if { $args != "{{}}" } {
- 	if { [string first "." $args] != -1 } {
- 	    set address_ [convert-dotted-ip-to-number $args]
- 	} else {
- 	    set address_ $args
- 	}
-     }
  }
  
  Node instproc set-node-addressMIPBS { args } {
--- 73,78 ----

*** ns-route.tcl	Wed Jun 21 15:23:25 2000
--- ns-route.tcl.old	Wed Jun 21 15:20:23 2000
***************
*** 206,213 ****
  				# a single line
  				set nh [$r lookup $i $j]
  			    if { $nh >= 0 } {
! 				set nj $Node_($j)
! 				$n1 add-route [$nj node-addr] [$link_($i:$nh) head]
  				###$n1 incr-rtgtable-size
  				}
  			} 
--- 206,212 ----
  				# a single line
  				set nh [$r lookup $i $j]
  			    if { $nh >= 0 } {
! 				$n1 add-route $j [$link_($i:$nh) head]
  				###$n1 incr-rtgtable-size
  				}
  			}