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CCNP: Optimizing Converged Networks v5.0 - Lab 4-3

Copyright

© 2007, Cisco Systems, Inc

Lab 4.3 TCP Header Compression

Learning Objectives

• Configure TCP header compression

• Verify TCP header compression

Topology Diagram

Scenario

In this lab, you will configure TCP header compression across a link and verify it
by establishing a Telnet session over the link.

This lab does not use the Pagent TGN application for traffic generation.

Step 1: Configure Addressing

Configure all of the physical interfaces shown in the diagram. Set the clock rate
on the serial link to 64000 and use the no shutdown command to enable all of
the interface addresses in the topology diagram.

R1(config)# interface serial0/0/0
R1(config-if)# ip address 172.16.12.1 255.255.255.0
R1(config-if)# clock rate 64000
R1(config-if)# no shutdown

R2(config)# interface serial0/0/0
R2(config-if)# ip address 172.16.12.2 255.255.255.0
R2(config-if)# no shutdown

Step 2: Enable Telnet Access on R2

Enable telnet access on R2 by setting a VTY line password to “cisco”.

R2(config-if)# line vty 0 4
R2(config-line)# password cisco

Step 3: Enable TCP Header Compression

TCP header compression is used to compress TCP headers in a network to
save bandwidth on a link. However, TCP header compression comes at a cost
in terms of processor time.

TCP header compression must be configured on both ends of the network to
compress and decompress packets. RTP header compression is configured
similarly, although it is not shown in this lab.

Issue the ip tcp header-compression command in interface configuration
mode to enable TCP header compression. A class-based form of the command
is used in the modular QoS CLI (MQC), but that information will be covered in
later labs. Configure this command on the Serial 0/0/0 interfaces on both R1
and R2.

R1(config)# interface serial0/0/0
R1(config-if)# ip tcp header-compression

R2(config)# interface serial0/0/0
R2(config-if)# ip tcp header-compression

Describe a traffic profile in which TCP header compression can be very useful.

Step 4: Verify TCP Header Compression

Issue the show ip tcp header-compression command to view statistics for
compressed TCP headers.

R1# show ip tcp header-compression
TCP/IP header compression statistics:
Interface Serial0/0/0 (compression on, VJ)
Rcvd: 0 total, 0 compressed, 0 errors, 0 status msgs
0 dropped, 0 buffer copies, 0 buffer failures
Sent: 0 total, 0 compressed, 0 status msgs, 0 not predicted
0 bytes saved, 0 bytes sent
Connect: 16 rx slots, 16 tx slots,
0 misses, 0 collisions, 0 negative cache hits, 16 free contexts

Generate some TCP traffic by connecting from R1 to R2 via Telnet.

R1# telnet 172.16.12.2
Trying 172.16.12.2 ... Open


User Access Verification

Password: cisco
R2> exit

[Connection to 172.16.12.2 closed by foreign host]
R1#

Verify that the TCP traffic was compressed.

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CCNP: Optimizing Converged Networks v5.0 - Lab 4-3

Copyright

© 2007, Cisco Systems, Inc

R1# show ip tcp header-compression
TCP/IP header compression statistics:
Interface Serial0/0/0 (compression on, VJ)
Rcvd: 17 total, 16 compressed, 0 errors, 0 status msgs
0 dropped, 0 buffer copies, 0 buffer failures
Sent: 19 total, 18 compressed, 0 status msgs, 0 not predicted
622 bytes saved, 181 bytes sent
4.43 efficiency improvement factor
Connect: 16 rx slots, 16 tx slots,
1 misses, 0 collisions, 0 negative cache hits, 16 free contexts
94% hit ratio, five minute miss rate 0 misses/sec, 0 max

R2# show ip tcp header-compression
TCP/IP header compression statistics:
Interface Serial0/0/0 (compression on, VJ)
Rcvd: 19 total, 18 compressed, 0 errors, 0 status msgs
0 dropped, 0 buffer copies, 0 buffer failures
Sent: 17 total, 16 compressed, 0 status msgs, 0 not predicted
537 bytes saved, 229 bytes sent
3.34 efficiency improvement factor
Connect: 16 rx slots, 16 tx slots,
1 misses, 0 collisions, 0 negative cache hits, 16 free contexts
94% hit ratio, five minute miss rate 0 misses/sec, 0 max

Given the numbers in the output of the commands shown above, identify how
the efficiency improvement factor is computed:

Final Configurations

R1# show run
!
hostname R1
!
interface Serial0/0/0
ip address 172.16.12.1 255.255.255.0
ip tcp header-compression
clock rate 64000
no shutdown
!
end

R2# show run
!
hostname R2
!
interface Serial0/0/0
ip address 172.16.12.2 255.255.255.0
ip tcp header-compression
no shutdown
!
line vty 0 4
password cisco
login
!
end

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CCNP: Optimizing Converged Networks v5.0 - Lab 4-3

Copyright

© 2007, Cisco Systems, Inc