Switched Multimegabit Data Service (SMDS)

Switched Multimegabit Data Service (SMDS) merupakan sebuah jaringan packet-switching publik, sekaligus termasuk ke dalam Teknologi jaringan WAN, Teknologi ini terutama digunakan untuk mengirim data dalam jumlah besar dengan proses yang sporadis. 

SMDS mirip dengan jaringan Telefoni Piblik (PSTN) dalam hal bahwa, para pengguna jaringan mendapatkan sebuah alamat yang unik, berupa nomor sepanjang 10 digit. Berbeda dengan Frame Relay, SMDS tidak menggunakan virtual circuit. Jalur-jalur komunikasi yang dibangun didalam jaringan sepenuhnya bersifat dinamis, sehingga setiap pengguna dapat mengirimkan data ke pengguna lainnya tanpa terlebih dahulu harus mendefiniikan jalur komunikasinya. Karena paket-paket SMDS dapat memiliki ukuran hingga 7168 byte, hampir semua protokol LAN lainnya dapat berkomunikasi dengan protokol ini tanpa masalah fragmentasi frame.

ni ada contoh configurasi SMDS pada Cisco

Let’s say there is a retail operation that has 3 sites in the metropolitan area. The organization wants to network the sites as if they were all on one LAN. How do they do it?

We have consulted with our service provider to create a VPN/closed user group amongst the sites. That means that we have our individual addresses (unicast) for our sites as well as our group addresses (multicast). We are now ready to configure our routers. We will perform the following operations in interface configuration mode.

Checklist for interface configuration:

• We are going to use point-to-point sub-interfaces for our example
• Set the Encapsulation method on the (main) interface
• Set the SMDS Address
• Create the ARP Address Mapping (to SMDS Multicast Address)
• Create a map for IP Multicast to SMDS Multicast Address
• Enable ARP

After we are all done, the HSSI interface might look like this.

interface Hssi5/0
 description SMDS DS-3 36QFDD555111
 no ip address
 encapsulation smds
 no ip route-cache optimum
 bandwidth 34000
 crc 32
!
interface Hssi5/0.1 point-to-point
 description smds
 ip address 172.16.31.1 255.255.255.0
 ip ospf network broadcast
 smds address c120.2202.6800
 smds multicast ARP e170.3202.4329 172.16.31.0 255.255.255.0
 smds multicast IP e170.3202.4329 172.16.31.0 255.255.255.0
 smds enable-arp

In this instance, we set the encapsulation on the major interface. Note that we recorded the circuit ID in the description. It is a good idea to have this information available without having to look it up in notebooks or documents on a workstations. This is especially helpful when you have a lot of circuits. The other two routers for this retail operation would have similar configurations. The IP addresses and SMDS addresses on the interfaces would of course be different. And that's it!

For routing, we might configure OSPF on our network, telling it the interface is a broadcast medium. EIGRP would be another obvious possibility.

(Note: for protocols other than IP, you have to statically map all peers, since there is no SMDS counterpart to ARP for matching layer 2 addresses to layer 3 addresses in the other network protocols).

*Peter J. Welcher and Alec L. Bullard