Implementing Host Services and Applications

Cisco IOS XR software Host Services and Applications features on the router are used primarily for checking network connectivity and the route a packet follows to reach a destination, mapping a hostname to an IP address or an IP address to a hostname, and transferring files between routers and UNIX workstations.

Prerequisites for implementing Host Services and Applications

Ensure to install the relevant optional RPM package before using the host services or applications.

HTTP clients

A HTTP client is a network utility that

  • transfers files and data from HTTP servers to devices over a network using the HTTP protocol,

  • enables configuration of connection, security, and transport parameters via http client command, and

  • and supports advanced features such as SSL/TLS options, source interface selection, and protocol versioning.

Configurable parameters for HTTP clients

HTTP client is available by default. You can configure http client settings or view and modify the existing settings. To configure the settings, use the http client command in XR configuration mode. 

RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:ios(config)#http client ?
connection          Configure HTTP Client connection
response            How long HTTP Client waits for a response from the server
                    for a request message before giving up
secure-verify-host  Verify that if server certificate is for the server it is known as
secure-verify-peer  Verify authenticity of the peer's certificate
source-interface    Specify interface for source address
ssl                 SSL configuration to be used for HTTPS requests
tcp-window-scale    Set tcp window-scale factor for High Latency links
version             HTTP Version to be used in HTTP requests
vrf                 Name of vrf
Table 1. Commands used to configure HTTP client settings

Parameters

Description
connection Configure HTTP Client connection by using either retry or timeout options.
response How long HTTP Client waits for a response from the server for a request message before giving up.
secure-verify-host Verify host in peer's certificate. To disable verifying this, you can use the command http client secure-verify-host disable
secure-verify-peer Verify authenticity of the peer's certificate.
source-interface Specifies the interface for source address for all outgoing HTTP connections. You can enter either an ipv4 or ipv6 address or both.
ssl version SSL version (configuration) to be used for HTTPS requests.
tcp-window-scale scale Set tcp window-scale factor for high latency links.
version version

HTTP version to be used in HTTP requests.

  • 1.0 - HTTP1.0 will be used for all HTTP requests.

  • 1.1 - HTTP1.1 will be used for all HTTP requests.

  • default libcurl - will use HTTP version automatically.
vrf name Name of vrf.

This example shows how to set the tcp window-scale to 8.

RP/0/RP0/CPU0:ios(config)#http client tcp-window-scale 8

This example shows how to set the HTTP version to 1.0.

RP/0/RP0/CPU0:ios(config)#http client version 1.0

Note

HTTP client uses libcurl version 7.30

TCP Overview

TCP is a connection-oriented protocol that specifies the format of data and acknowledgments that two computer systems exchange to transfer data. TCP also specifies the procedures the computers use to ensure that the data arrives correctly. TCP allows multiple applications on a system to communicate concurrently, because it handles all demultiplexing of the incoming traffic among the application programs.

TCP Dump File Converter

TCP dump file converter is a tool that converts ios-xr dump-files in binary format to user-friendly format such as PCAP or text.

It proves especially useful when you disable Non-Stop Routing (NSR) or experience a session flap on your system. During such incidents, by default, the TCP process running on the NCS system promptly stores the latest 200 packet traces in binary format within a temporary folder.

TCP dump packet traces also includes data about the configured routing protocols and the overall network traffic traversing your system. This data equips you with the necessary insights to identify and resolve issues within your network infrastructure, facilitating proactive network troubleshooting.

You can view the packet traces binary files in the user-readable format using the following methods:

  • You can use the show tcp dump-file <binary filename> command to view each binary file in text format manually. For more information, refer to View Binary Files in Text Format Manually.

    This process consumes much time, as you have to view each file manually one after another.

  • You can convert all stored packet traces in binary files into PCAP, text, or both using the tcp dump-file convert command. For more information, refer to Convert Binary Files to Readable Format Using TCP Dump File Converter.

    This active approach greatly improves the efficiency and ease of packet analysis during network troubleshooting.

Limitations and Restrictions for TCP Dump File Converter

  • The system only stores the most recent 200 message exchanges that occurred right before the session termination, when NSR is disabled, or during a session flap.

  • You can view only one binary file in text format using the show tcp dump-file <binary filename> command.

  • TCP dump files are generated by default for BGP, MSDP, MPLS LDP and SSH.

View Binary Files in Text Format Manually

Perform the following steps to view each packet traces binary file in text format without using the TCP dump file converter:
Procedure

Step 1

View the list of packet traces in binary files stored in the tcpdump folder using the show tcp dump-file list all command.

Example:
RP/0/RP0/CPU0:ios# show tcp dump-file list all
total 1176
-rw-r--r-- 1 root root 5927 Nov 22 12:42 31_0_0_126.179.20966.cl.1700656933
-rw-r--r-- 1 root root 5892 Nov 22 12:42 31_0_0_127.179.35234.cl.1700656933
-rw-r--r-- 1 root root 6148 Nov 22 12:42 31_0_0_149.179.54939.cl.1700656933
-rw-r--r-- 1 root root 5894 Nov 22 12:42 31_0_0_155.179.18134.cl.1700656933
-rw-r--r-- 1 root root 6063 Nov 22 12:42 31_0_0_156.179.25445.cl.1700656933
-rw-r--r-- 1 root root 5860 Nov 22 12:42 31_0_0_161.179.30859.cl.1700656933
-rw-r--r-- 1 root root 5832 Nov 22 12:42 31_0_0_173.179.36935.cl.1700656933
-rw-r--r-- 1 root root 5906 Nov 22 12:42 31_0_0_190.179.25642.cl.1700656933

Step 2

View each packet traces binary file in text format using the show tcp dump-file <binary filename> command.

Example:
RP/0/RP0/CPU0:ios# show tcp dump-file 10_106_0_73.179.34849.cl.1707424077 location 0/RP0/CPU0 
Filename: 10_106_0_73.179.34849.cl.1707424077

==============================================================
Connection state is CLOSED, I/O status: 0, socket status: 103
PCB 0x00007f86bc05e3b8, SO 0x7f86bc05e648, TCPCB 0x7f86bc0c3718, vrfid 0x60000000, 
Pak Prio: Medium, TOS: 192, TTL: 1, Hash index: 1593
Local host: 10.106.0.72, Local port: 179 (Local App PID: 11354)
Foreign host: 10.106.0.73, Foreign port: 34849
(Local App PID/instance/SPL_APP_ID: 11354/1/0)

Current send queue size in bytes: 0 (max 0)
Current receive queue size in bytes: 0 (max 0)  mis-ordered: 0 bytes
Current receive queue size in packets: 0 (max 0)

Timer          Starts    Wakeups         Next(msec)
Retrans        103448          8                0
SendWnd             0          0                0
TimeWait            1          0                0
AckHold        106815     106545                0
KeepAlive           1          0                0
PmtuAger            0          0                0
GiveUp              0          0                0
Throttle            0          0                0
FirstSyn            0          0                0

   iss: 161240548   snduna: 163206936   sndnxt: 163206936 
sndmax: 163206936   sndwnd: 63104       sndcwnd: 18120     
   irs: 3691232436  rcvnxt: 3693473072  rcvwnd: 26099   rcvadv: 3693499171

The above sample displays only a part of the actual output; the actual output displays more details.

Convert Binary Files to Readable Format Using TCP Dump File Converter

Perform the following steps to convert the dump packet traces in binary files into PCAP and text formats:
Procedure

Step 1

Execute the tcp dump-file convert all-formats all command to convert the dump packet traces in binary files into PCAP and text formats.

Example:
RP/0/RP0/CPU0:ios# tcp dump-file convert all-formats all
ascii file is saved at : /harddisk:/decoded_dumpfiles/text_tcpdump_peer_all_node0_RP0_CPU0_2024_3_19_10_8_53.462070.txt
pcap file is saved at : /harddisk:/decoded_dumpfiles/pcap_tcpdump_peer_all_node0_RP0_CPU0_2024_3_19_10_8_40.154838.pcap
[OK]

By default, the system stored the converted files in the "decoded_dumpfiles" folder on the "hard disk".

Using the location node-id and file <file path> keywords, you can save the converted TCP dump file to your desired location.

For example, tcp dump-file convert all-formats all location 0/RP0/CPU0 file /harddisk:/demo2 . 

RP/0/RP0/CPU0:ios# tcp dump-file convert all-formats all location 0/RP0/CPU0 file /harddisk:/demo2
ascii file is saved at : /harddisk:/demo2.txt
pcap file is saved at : /harddisk:/demo2.pcap
[OK]

Step 2

To view the converted text file in the CLI, use the run cat <text file path> command.

Example:
RP/0/RP0/CPU0:ios# run cat /harddisk:/decoded_dumpfiles/text_tcpdump_peer_all_node0_RP0_CPU0_2024_3_19_10_8_53.462070.txt
Filename: 2024_3_19_10_8_53.462070

==============================================================
Connection state is CLOSED, I/O status: 0, socket status: 103
PCB 0x0000000000f47a80, SO 0xf476d0, TCPCB 0xf6a370, vrfid 0x60000000, 
Pak Prio: Medium, TOS: 192, TTL: 255, Hash index: 563
Local host: 14:11:11::1, Local port: 47743 (Local App PID: 19579)
Foreign host: 14:11:11::2, Foreign port: 179
(Local App PID/instance/SPL_APP_ID: 19579/1/0)

Current send queue size in bytes: 0 (max 0)
Current receive queue size in bytes: 0 (max 0)  mis-ordered: 0 bytes
Current receive queue size in packets: 0 (max 0)

Timer          Starts    Wakeups         Next(msec)
Retrans            70          2                0
SendWnd             0          0                0
TimeWait            2          0                0
AckHold            66         61                0
KeepAlive           1          0                0
PmtuAger            0          0                0
GiveUp              0          0                0
Throttle            0          0                0
FirstSyn            1          1                0

   iss: 3113104891  snduna: 3113106213  sndnxt: 3113106213
sndmax: 3113106213  sndwnd: 31523       sndcwnd: 2832      
   irs: 4250126727  rcvnxt: 4250128049  rcvwnd: 31448   rcvadv: 4250159497

The above sample displays only a part of the actual output; the actual output displays more details.

Step 3

Copy the converted packet traces from the system to your local computer using the scp command and view the converted PCAP file.