Frame-relay compression and fragmentation.
Link optimization on frame-relay.
Using frame-relay, bandwidth is especially a concern.
It is possible to optimize this bandwidth in several ways.
I will concentrate this post about compression and fragmentation.
First off, with compression on frame-relay there several methods of accomplishing this.
You can have payload compression, tcp compression and RTP compression. How they are each
configured depends on your interface.
I will show how all of these are configured using a mix of point-to-point and multipoint interfaces.
Fragmentation is fundamentally a method to “chop up” packets when they reach a certain size. This feature is
also configured differently depending on the interface type. Again, i will show this on both types of interfaces.
Topology
R1: R1#sh run int s0/0 Building configuration... Current configuration : 117 bytes ! interface Serial0/0 no ip address encapsulation frame-relay clock rate 2000000 no frame-relay inverse-arp end R1#sh run int s0/0.12 Building configuration... Current configuration : 140 bytes ! interface Serial0/0.12 point-to-point ip address 12.12.12.1 255.255.255.0 snmp trap link-status frame-relay interface-dlci 102 end R1#sh run int s0/0.13 Building configuration... Current configuration : 146 bytes ! interface Serial0/0.13 multipoint ip address 13.13.13.1 255.255.255.0 snmp trap link-status frame-relay map ip 13.13.13.3 103 broadcast end
and R2:
R2#sh run int s0/0 Building configuration... Current configuration : 117 bytes ! interface Serial0/0 no ip address encapsulation frame-relay clock rate 2000000 no frame-relay inverse-arp end R2#sh run int s0/0.12 Building configuration... Current configuration : 140 bytes ! interface Serial0/0.12 point-to-point ip address 12.12.12.2 255.255.255.0 snmp trap link-status frame-relay interface-dlci 201 end
And finally R3:
R3#sh run int s0/0 Building configuration... Current configuration : 184 bytes ! interface Serial0/0 ip address 13.13.13.3 255.255.255.0 encapsulation frame-relay clock rate 2000000 frame-relay map ip 13.13.13.1 301 broadcast no frame-relay inverse-arp end
And lets verify reachability before we start messing about with things:
R1#ping 12.12.12.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 12.12.12.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/32/76 ms R1#ping 13.13.13.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 13.13.13.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/28/68 ms
Great. Now we are ready to apply some things.
First of, lets add some compression to payload traffic on our p2p interface towards R2.
On the subinterface itself, you can simply specify directly that you want to enable compression.
Check out your options:
R1(config-subif)#frame-relay payload-compression ? FRF9 FRF9 encapsulation data-stream cisco proprietary encapsulation packet-by-packet cisco proprietary encapsulation
They each work differently and with varying results. I will leave it up to you to figure out more about the individual algorithms they use.
For now, lets use packet-by-packet compression which is more CPU intensive than the rest of them.
R1(config-subif)#do ping 12.12.12.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 12.12.12.2, timeout is 2 seconds: ..
We are getting timeouts. Why?
Well, compression is a two way thing. It must be configured on each side of the PVC in order to maintain reachability.
Verify the compression by using:
R1#sh compress
Serial0/0
Software compression enabled
uncompressed bytes xmt/rcv 500/0
compressed bytes xmt/rcv 206/0
Compressed bytes sent: 206 bytes 0 Kbits/sec ratio: 2.427
Compressed bytes recv: 0 bytes 0 Kbits/sec
1 min avg ratio xmt/rcv 1.633/0.000
5 min avg ratio xmt/rcv 1.633/0.000
10 min avg ratio xmt/rcv 1.633/0.000
no bufs xmt 0 no bufs rcv 0
resyncs 0
Additional Stac Stats:
Transmit bytes: Uncompressed = 0 Compressed = 206
Received bytes: Compressed = 0 Uncompressed = 0
So its sending compressed information to the other side, but getting nothing back.
Lets configure R2 to use compression as well.
R2(config)#int s0/0.12 R2(config-subif)#frame-relay payload-compression packet-by-packet
Now, lets try a ping test from R1 again:
R1#ping 12.12.12.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 12.12.12.2, timeout is 2 seconds: !!!!!
Looks great. Lets check out the compression statistics on both R1 and R2:
R1#sh compress
Serial0/0
Software compression enabled
uncompressed bytes xmt/rcv 1400/1000
compressed bytes xmt/rcv 581/412
Compressed bytes sent: 581 bytes 0 Kbits/sec ratio: 2.409
Compressed bytes recv: 412 bytes 0 Kbits/sec ratio: 2.427
1 min avg ratio xmt/rcv 0.941/0.771
5 min avg ratio xmt/rcv 0.941/0.771
10 min avg ratio xmt/rcv 0.941/0.771
no bufs xmt 0 no bufs rcv 0
resyncs 0
Additional Stac Stats:
Transmit bytes: Uncompressed = 0 Compressed = 581
Received bytes: Compressed = 412 Uncompressed = 0
And R2:
R2#sh compress
Serial0/0
Software compression enabled
uncompressed bytes xmt/rcv 1000/1000
compressed bytes xmt/rcv 412/415
Compressed bytes sent: 412 bytes 0 Kbits/sec ratio: 2.427
Compressed bytes recv: 415 bytes 0 Kbits/sec ratio: 2.409
1 min avg ratio xmt/rcv 0.758/0.741
5 min avg ratio xmt/rcv 0.801/1.063
10 min avg ratio xmt/rcv 0.801/1.063
no bufs xmt 0 no bufs rcv 0
resyncs 0
Additional Stac Stats:
Transmit bytes: Uncompressed = 0 Compressed = 412
Received bytes: Compressed = 415 Uncompressed = 0
We can actually see that the routers have not transmitted anything that is not being compressed.
Before we move on, lets verify R1s connectivity to R3 again, just to be sure:
R1#ping 13.13.13.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 13.13.13.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/9/24 ms
Everything seems to be in working order.
Remember that R1s interface towards R3 is a multipoint subinterface and R3s interface towards R1 is the physical frame-relay interface.
Now if you just use the same command set as we did on the P2P interface, you will get the following error:
R1(config-subif)#frame-relay payload-compression packet-by-packet couldn't find map! Compression state not changed!
We need to apply this on our frame-relay map command in order for it to be working:
R1(config)#int s0/0.13 R1(config-subif)# frame-relay map ip 13.13.13.3 103 broadcast payload-compression packet-by-packet
And on R3s s0/0 interface as well:
R3(config-if)#int s0/0 R3(config-if)# frame-relay map ip 13.13.13.1 301 broadcast payload-compression packet-by-packet
Lets verify with a ping from R1:
R1#ping 13.13.13.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 13.13.13.3, timeout is 2 seconds: !!!!!
And show the compression:
R1#sh compress
Serial0/0
Software compression enabled
uncompressed bytes xmt/rcv 2900/2000
compressed bytes xmt/rcv 1205/824
Compressed bytes sent: 1205 bytes 0 Kbits/sec ratio: 2.406
Compressed bytes recv: 824 bytes 0 Kbits/sec ratio: 2.427
1 min avg ratio xmt/rcv 1.084/1.076
5 min avg ratio xmt/rcv 0.529/0.383
10 min avg ratio xmt/rcv 0.475/0.352
no bufs xmt 0 no bufs rcv 0
resyncs 0
Additional Stac Stats:
Transmit bytes: Uncompressed = 0 Compressed = 1205
Received bytes: Compressed = 824 Uncompressed = 0
Note that we dont see individual compression statistics for each dlci or subinterface.
Now lets change pace and look at some fragmentation. First off, i want to configure fragmentation on the link between
R1 and R2. Lets do it!
One very important thing to note, is the fact that fragmentation is part of the “traffic-shaping” command set.
We cannot do fragmentation without having frame-relay traffic-shaping enabled. This ofcourse has some consequences on our dlcis, but i will leave this unexplored in this post.
So, on R1, we need to create a map-class and apply this to our P2P interface.
R1(config)#map-class frame TST R1(config-map-class)#frame-relay fragment 400
Next, we need to apply this to our interface:
R1(config-map-class)#int s0/0.12 R1(config-subif)#frame-relay class TST
Lets verify without having traffic-shaping enabled:
R1#sh frame-relay fragment interface dlci frag-type size in-frag out-frag dropped-frag
And then lets enable traffic-shaping:
R1(config)#int s0/0 R1(config-if)#frame-relay traffic-sha R1(config-if)#^Z R1#sh *Mar 1 00:20:32.203: %SYS-5-CONFIG_I: Configured from console by console R1#sh frame-relay frag interface dlci frag-type size in-frag out-frag dropped-frag Se0/0.12 102 end-to-end 400 0 0 0
Now we can see that it has been enabled.
We are actually faced with a dilemma at the moment. Right now we have compression enabled on our interfaces which makes it very hard to test things out. Even if we did a ping with a size of 400 bytes, it would be compressed very heavily and thus not be fragmented. I have opted for disabling our compression to keep everything simple:
R1#sh run int s0/0.12 interface Serial0/0.12 point-to-point ip address 12.12.12.1 255.255.255.0 snmp trap link-status frame-relay class TST frame-relay interface-dlci 102 end
And R2:
R2(config-subif)#do sh run int s0/0.12 interface Serial0/0.12 point-to-point ip address 12.12.12.2 255.255.255.0 snmp trap link-status frame-relay interface-dlci 201 end
Now remember that a ping command adds 2 bytes of “overhead”, so lets ping from R1 to R2 with a payload of 398 bytes, which will make the packet 400 bytes in total:
R1#ping 12.12.12.2 size 398 Type escape sequence to abort. Sending 5, 398-byte ICMP Echos to 12.12.12.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/27/60 ms R1#sh frame frag interface dlci frag-type size in-frag out-frag dropped-frag Se0/0.12 102 end-to-end 400 0 0 0
Nothing has been fragmented yet.
Lets say 400 instead of 398:
R1#ping 12.12.12.2 size 400 Type escape sequence to abort. Sending 5, 400-byte ICMP Echos to 12.12.12.2, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) R1#sh frame frag interface dlci frag-type size in-frag out-frag dropped-frag Se0/0.12 102 end-to-end 400 0 10 0
We can see that we are now fragmenting our packets, but since R2 is not doing the same, the ping fails.
Lets add the same on R2:
R2(config)#map-class fra TST R2(config-map-class)#frame-relay fragment 400 R2(config-map-class)# R2(config-map-class)#int s0/0.12 R2(config-subif)#frame-relay class TST R2(config-subif)#int s0/0 R2(config-if)#frame-relay traffic-shaping
And verify:
R2#sh frame-relay fragment interface dlci frag-type size in-frag out-frag dropped-frag Se0/0.12 201 end-to-end 400 0 0 0
Lets try out the ping from R1 again:
R1#ping 12.12.12.2 size 400 Type escape sequence to abort. Sending 5, 400-byte ICMP Echos to 12.12.12.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 12/50/104 ms R1#sh frame frag interface dlci frag-type size in-frag out-frag dropped-frag Se0/0.12 102 end-to-end 400 10 20 0
And lets verify from R2:
R2#sh frame-relay fragment interface dlci frag-type size in-frag out-frag dropped-frag Se0/0.12 201 end-to-end 400 10 10 0
Awesome. Our fragmentation is now working as it should between R1 and R2.
This will have to do for the first segment of the post. Next time i will cover some of the RTP and TCP compression methods.
Take care!!