Description
DNS:
In this project, we will permit the hosts and routers to look into
data structures that map a hostname to an ipaddr. We will assume
that this info was obtained via some DNS protocol.
Routing for IP:
Develop a route cmd:
route h1 host_ip my_mac_to_send_on # route to one host
route h1 2.1 101
## we will probably not use this one, but I put it here solely
## for completeness about what it typically supported in a
## real network
route h1 net_ip my_mac_to_send_on # route to attached net
route h1 2 101
route h1 net_ip my_mac_to_send_on gateway_ip # route to remote net
route h1 2 101 1.2
route h1 def my_mac_to_send_on gateway_ip # default route
route h1 def 101 1.2
These examples create route table entries at host h1.
Note that each route cmd is performed on the route table on each
specified host after all hosts and switches are up. They are sent
from the interpreter to the hosts/routers as if they were commands
typed in at the console.
IP layer:
In this project, we will add support for simple routing which is
required for both IP and some ICMP operations. We will not support
fragmentation, so IP and ICMP are largely the same for us.
iptest from_host_or_router to_host_or_router_or_ipaddr
# iptest causes a ping to be sent from the specified host
# there is no ping reply
# more comments below
trtest from_host_or_router to_host_or_router_or_ipaddr payload
# traceroute test
# causes a traceroute to be sent from the specified host
# there is no traceroute reply
# more comments below
If it can not be determined how to send the message to the specified
hostname or ipaddr, simply print:
my_hostname: **** no route to host: hostname_or_ipaddr
Otherwise:
Every host/router at which either a ping or traceroute message
originates should print an informative message.
# my_hostname: sent ping to to_hostname
# my_hostname: sent traceroute to to_hostname
Every host/router that is the *destination* of a ping should print
an informative message.
# my_hostname: received ping from xx_hostname
Every host that is the *destination* of a traceroute, should print
an informative message.
# my_hostname: received traceroute from xx_hostname; route:
# h1 r1 r2 r3 …. rn h2
Format of IP-level message:
len 1 byte (len of entire msg)
ttl 1 byte
# start at 6; decrement by hosts (not switches); discard at 0
protocol 1 byte
# encapsulated protocol inside the packet’s payload
# icmp (iptest/ping, traceroute, etc) (see below)
src-ipaddr 2 bytes
dest-ipaddr 2 bytes
payload
# traceroute can collect the actual route taken in its payload
# field as it progresses to the final destination
ICMP protocols:
Recall that we used protocol 0 for early testing, and then 1 and 2 for
arp request and arp reply, respectively. In this project, we will add
new protocol types for icmp operations:
ping 3
traceroute 4
