IPTraf-ng User's Manual
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# 3.2. Lower Window

The lower window displays information about the other types of traffic on your network. The following protocols are detected internally:

- User Datagram Protocol (UDP)

- Internet Control Message Protocol (ICMP)

- Open Shortest-Path First (OSPF)

- Interior Gateway Routing Protocol (IGRP)

- Interior Gateway Protocol (IGP)

- Internet Group Management Protocol (IGMP)

- General Routing Encapsulation (GRE)

- Layer 2 Tunneling Protocol (L2TP)

- IPSec AH and ESP protocols (IPSec AH and IPSec ESP)

- Address Resolution Protocol (ARP)

- Reverse Address Resolution Protocol (RARP)

Other IP protocols are looked up from the `/etc/services` file. If `/etc/services` doesn't contain information about that protocol, the protocol number is indicated.

Non-IP packets are indicated as `Non-IP` in the lower window.

| Note
| The source and destination addresses for ARP and RARP entries are MAC addresses. Strictly speaking, ARP and RARP packets aren't IP packets, since they are not encapsulated in an IP datagram. They're just indicated because they are integral to proper IP operation on LANs.

For all packets in the lower window, only the first IP fragment is indicated (since that contains the header of the IP-encapsulated protocol) but with no further information from the encapsulated protocol.

UDP packets are also displayed in ``address`:`port`` format while ICMP entries also contain the ICMP message type. For easier location, each type of protocol is color-coded (only on color terminals such as the Linux console).

UDP

  Red on White

ICMP

  Yellow on Blue

OSPF

  Black on Cyan

IGRP

  Bright white on Cyan

IGP

  Red on Cyan

IGMP

  Bright green on Blue

GRE

  Blue on white

ARP

  Bright white on Red

RARP

  Bright white on Red

Other IP

  Yellow on red

Non-IP

  Yellow on Red

The lower window can hold up to 512 entries. You can scroll the lower window by using the W key to move the Active indicator to it, and by using the Up and Down cursor keys. The lower window automatically scrolls every time a new entry is added, and either the first entry or last entry is visible. Upon reaching 512 entries, old entries are thrown out as new entries are added.

Some entries may be too long to completely fit in a screen line. You can use the Left and Right cursor keys to vertically scroll the lower window when it is marked `Active`. If your terminal can be resized (e.g. xterm), you may do so before starting IPTraf-ng.

Entries for packets received on LAN interfaces also include the source MAC address of the LAN host which delivered it. This behavior is enabled by turning on the Source MAC addrs in traffic monitor toggle in the Configure... menu.

## 3.2.1. Entry Details

In general, the entries in the lower window indicate the protocol, the IP datagram size (full frame size for non-IP, including ARP and RARP), the source address, the destination address, and the network interface the packet was detected on. However, some protocols have a little more information.

### 3.2.1.1. ICMP

ICMP entries are displayed in this format:

    ICMP type [(subtype)] (size bytes) from source to destination
    [(src HWaddr srcMACaddress)] on interface

where type could be any of the following:

`echo req, echo rply`

  ICMP echo request and reply. Usually used by the ping program and other network monitoring and diagnostic program.

`dest unrch`

  ICMP destination unreachable. Something failed to reach its target. The dest unreach type is supplemented with a further indicator of the problem. Destination unreachable messages for TCP traffic causes the corresponding TCP entry in the upper window to be made available for reuse by new connections.

`redirct`

  ICMP redirect. Usually generated by a router to tell a host that a better gateway is available.

`src qnch`

  The ICMP source quench is used to stop a host from transmitting. It's a flow control mechanism for IP.

`time excd`

  Indicates a packet's time-to-live value expired before it got to its destination. Mostly happens if a destination is too far away. Also used by the traceroute program.

`router adv`

  ICMP router advertisement

`router sol`

  ICMP router solicitation

`timestmp req`

  ICMP timestamp request

`timestmp rep`

  ICMP timestamp reply

`info req`

  ICMP information request

`info rep`

  ICMP information reply

`addr mask req`

  ICMP address mask request

`addr mask rep`

  ICMP address mask reply

`param prob`

  ICMP parameter problem

`bad/unknown`

  An unrecognized ICMP packet was received, or the packet is corrupted.

The destination unreachable message also includes information on the type of error encountered. Here are the destination unreachable codes:

`ntwk`

  network unreachable

`host`

  host unreachable

`proto`

  protocol unreachable

`port`

  port unreachable

`pkt fltrd`

  packet filtered (normally by an access rule on a router or firewall)

`DF set`

  the packet has to be fragmented somewhere, but its don't fragment (DF) bit is set.

`src rte fail`

  source route failed

`src isltd`

  source isolated (obsolete)

`net comm denied`

  network communication denied

`host comm denied`

  host communication denied

`net unrch for TOS`

  network unreachable for specified IP type-of-service

`host unrch for TOS`

  host unreachable for specified IP type-of-service

`prec violtn`

  precedence violation

`prec cutoff`

  precedence cutoff

`dest net unkn`

  destination network unknown

`dest host unkn`

  destination network unknown

For more information on ICMP, see RFC 792.

### 3.2.1.2. OSPF

OSPF messages also include a little more information. The format of an OSPF message in the window is:

    OSPF type (a=area r=router) (sizebytes) from source to destination
    [(src HWaddr srcMACaddress)] on interface

The type can be one of the following:

`hlo`

  OSPF hello. Hello messages establish OSPF communications and keep routers informed of each other's presence.

`DB desc`

  OSPF Database Description

`LSR`

  OSPF Link State Request

`LSU`

  OSPF Link State Update. Messages indicating the states of the OSPF network links

`LSA`

  OSPF Link State Acknowledgment

The entries in parentheses:

`a=`area``

  The area number of the OSPF message

`r=`router``

  The IP address of the router that generated the message. It is not necessarily the same as the source address of the encapsulating IP packet.

Many times, the destination addresses for OSPF packets are class D multicast addresses in standard dotted decimal notation or (if reverse lookup is enabled), hosts under the `MCAST.NET` domain. Such multicast addresses are defined as follows:

`224.0.0.5 (OSPF-ALL.MCAST.NET)`

  OSPF all routers

`224.0.0.6 (OSPF-DSIG.MCAST.NET)`

  OSPF all designated routers

See RFC 1247 for details on the OSPF protocol.

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