MPLS - LDP and LSP

In this section, we will see about LDP protocol and MPLS LSP and how it is formed using LDP.

LDP overview-

The Label Distribution Protocol (LDP) is used to establish MPLS and to form LSPs .It establishes LSPs that follow the existing IP routing table made by IGP, and is particularly well suited for establishing a full mesh of 

LSPs between all of the routers on the network.

LDP can operate in many modes to suit different requirements; however the most common usage is unsolicited mode, which sets up a full mesh of tunnels between routers.

• In solicited mode, the ingress router sends an LDP label request to the next hop router, as determined from its IP routing table. This request is forwarded on through the network hop-by-hop by each router. Once the request reaches the egress router, a return message is generated. This message confirms the LSP and tells each router the label mapping to use on each link for that LSP.

Solicited Distribution

• In unsolicited mode, the egress routers broadcast label mappings for each external link to all of their neighbors. These broadcasts are spread across every link through the network until they reach the ingress routers. Across each hop, they inform the upstream router of the label mapping to use for each external link, and by flooding the network they establish LSPs between all of the external links.

Unsolicited Distribution

The main advantage of LDP is the ease of setting up a full mesh of tunnels using unsolicited mode, so it is most often used in this mode to set up the underlying mesh of tunnels needed by MPLS Layer 3 VPNs.

LSP – Label switched path

•  A Label Switched Path (LSP) is a sequence of LSRs that forward the packets of a certain forwarding equivalence class.
• MPLS unicast IP forwarding builds LSPs based on the output of IP routing protocols.
• LDP advertises the labels only for individual segments in the LSP.
• LSPs are unidirectional
• Return traffic uses different LSP (usually reverse path because the most routing protocol provide symmetrical routing)

An LSP can take a different path from the one chosen by an IP routing protocol.(MPLS TE)           

The IP Routing protocols determine the path of LSP.

LSP is made by IGP

• In MPLS network each router will have LIB (label information base) and LFIB.    In LIB all label are installed then by calculating best next hop. Best labels is installed in LFIB to process the labels for particular network, In this way LSP builds

• LDP propagates the labels to converge the path to LSP.

• We also have other label information which is in LIB, So In this way we can converge fast in failure of link. Since we are having the alternative label information with us. This is known as Liberal retention mode.

 Hope this post will help you to understanding LDP and LSP . 

 For feedback and queries, Plz put comment with your mail id... 

IPFIX and Netflow

Some days before,  I was reading IPFIX. But I was searching something which can help me to understand difference between IPFIX and Netlfow. As we all know Netflow is from Cisco. Many of Engineers are not aware that IPFIX is also flow export like Netflow. But it is 

industry standard. Here let’s see difference between Netflow and IPFIX.

Netflow -

When Cisco first introduced NetFlow a while ago, it was a caching technique based on "flows". It still is, but the emphasis is now on statistics collection.

A network flow is a unidirectional stream of packets, identified by source and destination IP addresses, IP protocol, source and destination ports , and Type of Service  byte. Inbound interface and other information can be tracked per flow. The crucial statistics tracked by NetFlow are packet and byte counts source to destination.

When you enable NetFlow on a router or switch, statistics are collected on the IP traffic passing through that device. The flow data can then be exported to a collection system aka Netflow server for post-processing and storage. Netflow analyzer software provides interactive reports to us as per our requirement.

NetFlow data export allows you to gather data from across a network about the traffic passing through that network. 

For more information about Cisco Netflow Technical and configuration – Plz visit –

http://www.cisco.com/en/US/docs/ios/fnetflow/configuration/guide/fnetflow_overview_ps6441_TSD_Products_Configuration_Guide_Chapter.html

IPFIX - 

The IETF has been working to standardize NetFlow for all vendors. The effort is named IPFIX, which stands for IP Flow Information eXport.

The IETF considered working implementations as a starting point, and elected to work from Cisco NetFlow version 9. Version 9 extends classic NetFlow by using templates to describe the flow records. This provides extensibility. The charter for the working group also lead them to allow securing the flow information -- SCTP secure stream transport can be used instead of TCP or UDP for transport. IPsec or TLS can also be used. 

The IPFIX standard also allows for sampled data, which reduces the burden on devices of classifying and reporting on each and every packet. Cisco is recommending random sampling  to ensure you don't miss flows.

Here have a look for IPFIX configuration for Maipu Router –

Maipu Router configuration:

Command	Description
router(config)# int fastethernet1	Enter the interface; the interface is connected to the internal management network.
router(config-if-fastethernet1)#ip address 50.1.1.1 255.255.255.0	Configure the IP address.
router(config-if-fastethernet1)#exit	Exit the interface.
router(config)#ip flow enable	Enable the flow forwarding
router(config)#int fastethernet0	Enter the interface; the interface is the IPFIX traffic monitoring point.
router(config-if-fastethernet0)#ip address 128.255.42.172 255.255.252.0	Configure the IP address.
router(config-if-fastethernet0)#ip route-cache flow	Enable the flow forwarding on the interface.
router(config-if-fastethernet0)#ipfix ingress	Enable IPFIX on the interface and monitor the ingress traffic.
router(config-if-fastethernet0)#exit	Exit the interface
router(config)#ipfix destination 50.1.1.2 8888	Configure the destination address of the IPfix packet and UDP destination port number

You can enable IPFIX for egress also. Its as per your requirement.

Monitoring Commands

Command	Description
show ipfix statistics	To display the IPFIX statistics data
show ipfix flow interface-name {ingress | egress} [top top-N]	To display the current ingress/egress flow information o of the specified interface
clear ipfix statistics	To clear up the statistics data of the IPFIX

Here is example output, not same with above configuration.

router#show ipfix flow g0 ingress

Displayed Result：

PRO SRC           DST        IF                  TOS SP    DP    PKTS    BYTES

17  128.255.41.200  128.255.41.255  gigaethernet0        0   138   138   1          229

17  128.255.42.17   128.255.43.255  gigaethernet0        0   138   138   1          208

17  128.255.42.190  128.255.43.255  gigaethernet0        0   137   137   3          234

17  128.255.40.68   128.255.43.255  gigaethernet0        0   138   138   2          436

17  128.255.42.190  128.255.43.255  gigaethernet0        0   138   138   2          404

Description and analysis:

PRO: IP protocol number of the monitoring flow;

SRC: The IP source address of the monitoring flow;

DST: The IP destination address of the monitoring flow;

TOS: The TOS of the monitoring flow;

SP: The source port number of the monitoring flow;

DP: The destination port number of the monitoring flow;

PKTS: The packet statistics of the monitoring flow;

BYTES: The byte statistics of the monitoring flow;

The above information displays the current statistics information of all IP flows entering from g0.

Hope the above information is informative for you..

For feedback and queries, Plz comment with your mail id…